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This is dash.info, produced by makeinfo version 6.8 from dash.texi.
This manual is for Dash version 2.19.1.
Copyright © 2012–2024 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this
document under the terms of the GNU Free Documentation License,
Version 1.3 or any later version published by the Free Software
Foundation; with the Invariant Sections being “GNU General Public
License,” and no Front-Cover Texts or Back-Cover Texts. A copy of
the license is included in the section entitled “GNU Free
Documentation License”.
INFO-DIR-SECTION Emacs
START-INFO-DIR-ENTRY
* Dash: (dash.info). A modern list library for GNU Emacs.
END-INFO-DIR-ENTRY

File: dash.info, Node: Top, Next: Installation, Up: (dir)
Dash
****
This manual is for Dash version 2.19.1.
Copyright © 2012–2024 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this
document under the terms of the GNU Free Documentation License,
Version 1.3 or any later version published by the Free Software
Foundation; with the Invariant Sections being “GNU General Public
License,” and no Front-Cover Texts or Back-Cover Texts. A copy of
the license is included in the section entitled “GNU Free
Documentation License”.
* Menu:
* Installation:: Installing and configuring Dash.
* Functions:: Dash API reference.
* Development:: Contributing to Dash development.
Appendices
* FDL:: The license for this documentation.
* GPL:: Conditions for copying and changing Dash.
* Index:: Index including functions and macros.
— The Detailed Node Listing —
Installation
* Using in a package:: Listing Dash as a package dependency.
* Fontification of special variables:: Font Lock of anaphoric macro variables.
* Info symbol lookup:: Looking up Dash symbols in this manual.
Functions
* Maps::
* Sublist selection::
* List to list::
* Reductions::
* Unfolding::
* Predicates::
* Partitioning::
* Indexing::
* Set operations::
* Other list operations::
* Tree operations::
* Threading macros::
* Binding::
* Side effects::
* Destructive operations::
* Function combinators::
Development
* Contribute:: How to contribute.
* Contributors:: List of contributors.

File: dash.info, Node: Installation, Next: Functions, Prev: Top, Up: Top
1 Installation
**************
Dash is available on GNU ELPA (https://elpa.gnu.org/), GNU-devel ELPA
(https://elpa.gnu.org/devel/), and MELPA (https://melpa.org/), and can
be installed with the standard command ‘package-install’ (*note
(emacs)Package Installation::).
‘M-x package-install <RET> dash <RET>’
Install the Dash library.
Alternatively, you can just dump ‘dash.el’ in your ‘load-path’
somewhere (*note (emacs)Lisp Libraries::).
* Menu:
* Using in a package:: Listing Dash as a package dependency.
* Fontification of special variables:: Font Lock of anaphoric macro variables.
* Info symbol lookup:: Looking up Dash symbols in this manual.

File: dash.info, Node: Using in a package, Next: Fontification of special variables, Up: Installation
1.1 Using in a package
======================
If you use Dash in your own package, be sure to list it as a dependency
in the library’s headers as follows (*note (elisp)Library Headers::).
;; Package-Requires: ((dash "2.19.1"))

File: dash.info, Node: Fontification of special variables, Next: Info symbol lookup, Prev: Using in a package, Up: Installation
1.2 Fontification of special variables
======================================
The autoloaded minor mode ‘dash-fontify-mode’ is provided for optional
fontification of anaphoric Dash variables (‘it’, ‘acc’, etc.) in Emacs
Lisp buffers using search-based Font Lock (*note (emacs)Font Lock::).
In older Emacs versions which do not dynamically detect macros, the
minor mode also fontifies calls to Dash macros.
To automatically enable the minor mode in all Emacs Lisp buffers,
just call its autoloaded global counterpart ‘global-dash-fontify-mode’,
either interactively or from your ‘user-init-file’:
(global-dash-fontify-mode)

File: dash.info, Node: Info symbol lookup, Prev: Fontification of special variables, Up: Installation
1.3 Info symbol lookup
======================
While editing Elisp files, you can use ‘C-h S’ (‘info-lookup-symbol’) to
look up Elisp symbols in the relevant Info manuals (*note (emacs)Info
Lookup::). To enable the same for Dash symbols, use the command
‘dash-register-info-lookup’. It can be called directly when needed, or
automatically from your ‘user-init-file’. For example:
(with-eval-after-load 'info-look
(dash-register-info-lookup))

File: dash.info, Node: Functions, Next: Development, Prev: Installation, Up: Top
2 Functions
***********
This chapter contains reference documentation for the Dash API
(Application Programming Interface). The names of all public functions
defined in the library are prefixed with a dash character (‘-’).
The library also provides anaphoric macro versions of functions where
that makes sense. The names of these macros are prefixed with two
dashes (‘--’) instead of one.
For instance, while the function ‘-map’ applies a function to each
element of a list, its anaphoric counterpart ‘--map’ evaluates a form
with the local variable ‘it’ temporarily bound to the current list
element instead.
;; Normal version.
(-map (lambda (n) (* n n)) '(1 2 3 4))
⇒ (1 4 9 16)
;; Anaphoric version.
(--map (* it it) '(1 2 3 4))
⇒ (1 4 9 16)
The normal version can, of course, also be written as in the
following example, which demonstrates the utility of both versions.
(defun my-square (n)
"Return N multiplied by itself."
(* n n))
(-map #'my-square '(1 2 3 4))
⇒ (1 4 9 16)
* Menu:
* Maps::
* Sublist selection::
* List to list::
* Reductions::
* Unfolding::
* Predicates::
* Partitioning::
* Indexing::
* Set operations::
* Other list operations::
* Tree operations::
* Threading macros::
* Binding::
* Side effects::
* Destructive operations::
* Function combinators::

File: dash.info, Node: Maps, Next: Sublist selection, Up: Functions
2.1 Maps
========
Functions in this category take a transforming function, which is then
applied sequentially to each or selected elements of the input list.
The results are collected in order and returned as a new list.
-- Function: -map (fn list)
Apply FN to each item in LIST and return the list of results.
This function’s anaphoric counterpart is ‘--map’.
(-map (lambda (num) (* num num)) '(1 2 3 4))
⇒ (1 4 9 16)
(-map #'1+ '(1 2 3 4))
⇒ (2 3 4 5)
(--map (* it it) '(1 2 3 4))
⇒ (1 4 9 16)
-- Function: -map-when (pred rep list)
Use PRED to conditionally apply REP to each item in LIST. Return a
copy of LIST where the items for which PRED returns ‘nil’ are
unchanged, and the rest are mapped through the REP function.
Alias: ‘-replace-where’
See also: ‘-update-at’ (*note -update-at::)
(-map-when 'even? 'square '(1 2 3 4))
⇒ (1 4 3 16)
(--map-when (> it 2) (* it it) '(1 2 3 4))
⇒ (1 2 9 16)
(--map-when (= it 2) 17 '(1 2 3 4))
⇒ (1 17 3 4)
-- Function: -map-first (pred rep list)
Use PRED to determine the first item in LIST to call REP on.
Return a copy of LIST where the first item for which PRED returns
non-‘nil’ is replaced with the result of calling REP on that item.
See also: ‘-map-when’ (*note -map-when::), ‘-replace-first’ (*note
-replace-first::)
(-map-first 'even? 'square '(1 2 3 4))
⇒ (1 4 3 4)
(--map-first (> it 2) (* it it) '(1 2 3 4))
⇒ (1 2 9 4)
(--map-first (= it 2) 17 '(1 2 3 2))
⇒ (1 17 3 2)
-- Function: -map-last (pred rep list)
Use PRED to determine the last item in LIST to call REP on. Return
a copy of LIST where the last item for which PRED returns non-‘nil’
is replaced with the result of calling REP on that item.
See also: ‘-map-when’ (*note -map-when::), ‘-replace-last’ (*note
-replace-last::)
(-map-last 'even? 'square '(1 2 3 4))
⇒ (1 2 3 16)
(--map-last (> it 2) (* it it) '(1 2 3 4))
⇒ (1 2 3 16)
(--map-last (= it 2) 17 '(1 2 3 2))
⇒ (1 2 3 17)
-- Function: -map-indexed (fn list)
Apply FN to each index and item in LIST and return the list of
results. This is like ‘-map’ (*note -map::), but FN takes two
arguments: the index of the current element within LIST, and the
element itself.
This function’s anaphoric counterpart is ‘--map-indexed’.
For a side-effecting variant, see also ‘-each-indexed’ (*note
-each-indexed::).
(-map-indexed (lambda (index item) (- item index)) '(1 2 3 4))
⇒ (1 1 1 1)
(--map-indexed (- it it-index) '(1 2 3 4))
⇒ (1 1 1 1)
(-map-indexed #'* '(1 2 3 4))
⇒ (0 2 6 12)
-- Function: -annotate (fn list)
Pair each item in LIST with the result of passing it to FN.
Return an alist of (RESULT . ITEM), where each ITEM is the
corresponding element of LIST, and RESULT is the value obtained by
calling FN on ITEM.
This function’s anaphoric counterpart is ‘--annotate’.
(-annotate #'1+ '(1 2 3))
⇒ ((2 . 1) (3 . 2) (4 . 3))
(-annotate #'length '((f o o) (bar baz)))
⇒ ((3 f o o) (2 bar baz))
(--annotate (> it 1) '(0 1 2 3))
⇒ ((nil . 0) (nil . 1) (t . 2) (t . 3))
-- Function: -splice (pred fun list)
Splice lists generated by FUN in place of items satisfying PRED in
LIST.
Call PRED on each element of LIST. Whenever the result of PRED is
‘nil’, leave that ‘it’ as-is. Otherwise, call FUN on the same ‘it’
that satisfied PRED. The result should be a (possibly empty) list
of items to splice in place of ‘it’ in LIST.
This can be useful as an alternative to the ‘,@’ construct in a ‘`’
structure, in case you need to splice several lists at marked
positions (for example with keywords).
This function’s anaphoric counterpart is ‘--splice’.
See also: ‘-splice-list’ (*note -splice-list::), ‘-insert-at’
(*note -insert-at::).
(-splice #'numberp (lambda (n) (list n n)) '(a 1 b 2))
⇒ (a 1 1 b 2 2)
(--splice t (list it it) '(1 2 3 4))
⇒ (1 1 2 2 3 3 4 4)
(--splice (eq it :magic) '((magical) (code)) '((foo) :magic (bar)))
⇒ ((foo) (magical) (code) (bar))
-- Function: -splice-list (pred new-list list)
Splice NEW-LIST in place of elements matching PRED in LIST.
See also: ‘-splice’ (*note -splice::), ‘-insert-at’ (*note
-insert-at::)
(-splice-list 'keywordp '(a b c) '(1 :foo 2))
⇒ (1 a b c 2)
(-splice-list 'keywordp nil '(1 :foo 2))
⇒ (1 2)
(--splice-list (keywordp it) '(a b c) '(1 :foo 2))
⇒ (1 a b c 2)
-- Function: -mapcat (fn list)
Return the concatenation of the result of mapping FN over LIST.
Thus function FN should return a list.
(-mapcat 'list '(1 2 3))
⇒ (1 2 3)
(-mapcat (lambda (item) (list 0 item)) '(1 2 3))
⇒ (0 1 0 2 0 3)
(--mapcat (list 0 it) '(1 2 3))
⇒ (0 1 0 2 0 3)
-- Function: -copy (list)
Create a shallow copy of LIST.
(-copy '(1 2 3))
⇒ (1 2 3)
(let ((a '(1 2 3))) (eq a (-copy a)))
⇒ nil

File: dash.info, Node: Sublist selection, Next: List to list, Prev: Maps, Up: Functions
2.2 Sublist selection
=====================
Functions returning a sublist of the original list.
-- Function: -filter (pred list)
Return a new list of the items in LIST for which PRED returns
non-‘nil’.
Alias: ‘-select’.
This function’s anaphoric counterpart is ‘--filter’.
For similar operations, see also ‘-keep’ (*note -keep::) and
‘-remove’ (*note -remove::).
(-filter (lambda (num) (= 0 (% num 2))) '(1 2 3 4))
⇒ (2 4)
(-filter #'natnump '(-2 -1 0 1 2))
⇒ (0 1 2)
(--filter (= 0 (% it 2)) '(1 2 3 4))
⇒ (2 4)
-- Function: -remove (pred list)
Return a new list of the items in LIST for which PRED returns
‘nil’.
Alias: ‘-reject’.
This function’s anaphoric counterpart is ‘--remove’.
For similar operations, see also ‘-keep’ (*note -keep::) and
‘-filter’ (*note -filter::).
(-remove (lambda (num) (= 0 (% num 2))) '(1 2 3 4))
⇒ (1 3)
(-remove #'natnump '(-2 -1 0 1 2))
⇒ (-2 -1)
(--remove (= 0 (% it 2)) '(1 2 3 4))
⇒ (1 3)
-- Function: -remove-first (pred list)
Remove the first item from LIST for which PRED returns non-‘nil’.
This is a non-destructive operation, but only the front of LIST
leading up to the removed item is a copy; the rest is LIST’s
original tail. If no item is removed, then the result is a
complete copy.
Alias: ‘-reject-first’.
This function’s anaphoric counterpart is ‘--remove-first’.
See also ‘-map-first’ (*note -map-first::), ‘-remove-item’ (*note
-remove-item::), and ‘-remove-last’ (*note -remove-last::).
(-remove-first #'natnump '(-2 -1 0 1 2))
⇒ (-2 -1 1 2)
(-remove-first #'stringp '(1 2 "first" "second"))
⇒ (1 2 "second")
(--remove-first (> it 3) '(1 2 3 4 5 6))
⇒ (1 2 3 5 6)
-- Function: -remove-last (pred list)
Remove the last item from LIST for which PRED returns non-‘nil’.
The result is a copy of LIST regardless of whether an element is
removed.
Alias: ‘-reject-last’.
This function’s anaphoric counterpart is ‘--remove-last’.
See also ‘-map-last’ (*note -map-last::), ‘-remove-item’ (*note
-remove-item::), and ‘-remove-first’ (*note -remove-first::).
(-remove-last #'natnump '(1 3 5 4 7 8 10 -11))
⇒ (1 3 5 4 7 8 -11)
(-remove-last #'stringp '(1 2 "last" "second"))
⇒ (1 2 "last")
(--remove-last (> it 3) '(1 2 3 4 5 6 7 8 9 10))
⇒ (1 2 3 4 5 6 7 8 9)
-- Function: -remove-item (item list)
Return a copy of LIST with all occurrences of ITEM removed. The
comparison is done with ‘equal’.
(-remove-item 3 '(1 2 3 2 3 4 5 3))
⇒ (1 2 2 4 5)
(-remove-item 'foo '(foo bar baz foo))
⇒ (bar baz)
(-remove-item "bob" '("alice" "bob" "eve" "bob"))
⇒ ("alice" "eve")
-- Function: -non-nil (list)
Return a copy of LIST with all ‘nil’ items removed.
(-non-nil '(nil 1 nil 2 nil nil 3 4 nil 5 nil))
⇒ (1 2 3 4 5)
(-non-nil '((nil)))
⇒ ((nil))
(-non-nil ())
⇒ ()
-- Function: -slice (list from &optional to step)
Return copy of LIST, starting from index FROM to index TO.
FROM or TO may be negative. These values are then interpreted
modulo the length of the list.
If STEP is a number, only each STEPth item in the resulting section
is returned. Defaults to 1.
(-slice '(1 2 3 4 5) 1)
⇒ (2 3 4 5)
(-slice '(1 2 3 4 5) 0 3)
⇒ (1 2 3)
(-slice '(1 2 3 4 5 6 7 8 9) 1 -1 2)
⇒ (2 4 6 8)
-- Function: -take (n list)
Return a copy of the first N items in LIST. Return a copy of LIST
if it contains N items or fewer. Return ‘nil’ if N is zero or
less.
See also: ‘-take-last’ (*note -take-last::).
(-take 3 '(1 2 3 4 5))
⇒ (1 2 3)
(-take 17 '(1 2 3 4 5))
⇒ (1 2 3 4 5)
(-take 0 '(1 2 3 4 5))
⇒ ()
-- Function: -take-last (n list)
Return a copy of the last N items of LIST in order. Return a copy
of LIST if it contains N items or fewer. Return ‘nil’ if N is zero
or less.
See also: ‘-take’ (*note -take::).
(-take-last 3 '(1 2 3 4 5))
⇒ (3 4 5)
(-take-last 17 '(1 2 3 4 5))
⇒ (1 2 3 4 5)
(-take-last 1 '(1 2 3 4 5))
⇒ (5)
-- Function: -drop (n list)
Return the tail (not a copy) of LIST without the first N items.
Return ‘nil’ if LIST contains N items or fewer. Return LIST if N
is zero or less.
For another variant, see also ‘-drop-last’ (*note -drop-last::).
(-drop 3 '(1 2 3 4 5))
⇒ (4 5)
(-drop 17 '(1 2 3 4 5))
⇒ ()
(-drop 0 '(1 2 3 4 5))
⇒ (1 2 3 4 5)
-- Function: -drop-last (n list)
Return a copy of LIST without its last N items. Return a copy of
LIST if N is zero or less. Return ‘nil’ if LIST contains N items
or fewer.
See also: ‘-drop’ (*note -drop::).
(-drop-last 3 '(1 2 3 4 5))
⇒ (1 2)
(-drop-last 17 '(1 2 3 4 5))
⇒ ()
(-drop-last 0 '(1 2 3 4 5))
⇒ (1 2 3 4 5)
-- Function: -take-while (pred list)
Take successive items from LIST for which PRED returns non-‘nil’.
PRED is a function of one argument. Return a new list of the
successive elements from the start of LIST for which PRED returns
non-‘nil’.
This function’s anaphoric counterpart is ‘--take-while’.
For another variant, see also ‘-drop-while’ (*note -drop-while::).
(-take-while #'even? '(1 2 3 4))
⇒ ()
(-take-while #'even? '(2 4 5 6))
⇒ (2 4)
(--take-while (< it 4) '(1 2 3 4 3 2 1))
⇒ (1 2 3)
-- Function: -drop-while (pred list)
Drop successive items from LIST for which PRED returns non-‘nil’.
PRED is a function of one argument. Return the tail (not a copy)
of LIST starting from its first element for which PRED returns
‘nil’.
This function’s anaphoric counterpart is ‘--drop-while’.
For another variant, see also ‘-take-while’ (*note -take-while::).
(-drop-while #'even? '(1 2 3 4))
⇒ (1 2 3 4)
(-drop-while #'even? '(2 4 5 6))
⇒ (5 6)
(--drop-while (< it 4) '(1 2 3 4 3 2 1))
⇒ (4 3 2 1)
-- Function: -select-by-indices (indices list)
Return a list whose elements are elements from LIST selected as
‘(nth i list)‘ for all i from INDICES.
(-select-by-indices '(4 10 2 3 6) '("v" "e" "l" "o" "c" "i" "r" "a" "p" "t" "o" "r"))
⇒ ("c" "o" "l" "o" "r")
(-select-by-indices '(2 1 0) '("a" "b" "c"))
⇒ ("c" "b" "a")
(-select-by-indices '(0 1 2 0 1 3 3 1) '("f" "a" "r" "l"))
⇒ ("f" "a" "r" "f" "a" "l" "l" "a")
-- Function: -select-columns (columns table)
Select COLUMNS from TABLE.
TABLE is a list of lists where each element represents one row. It
is assumed each row has the same length.
Each row is transformed such that only the specified COLUMNS are
selected.
See also: ‘-select-column’ (*note -select-column::),
‘-select-by-indices’ (*note -select-by-indices::)
(-select-columns '(0 2) '((1 2 3) (a b c) (:a :b :c)))
⇒ ((1 3) (a c) (:a :c))
(-select-columns '(1) '((1 2 3) (a b c) (:a :b :c)))
⇒ ((2) (b) (:b))
(-select-columns nil '((1 2 3) (a b c) (:a :b :c)))
⇒ (nil nil nil)
-- Function: -select-column (column table)
Select COLUMN from TABLE.
TABLE is a list of lists where each element represents one row. It
is assumed each row has the same length.
The single selected column is returned as a list.
See also: ‘-select-columns’ (*note -select-columns::),
‘-select-by-indices’ (*note -select-by-indices::)
(-select-column 1 '((1 2 3) (a b c) (:a :b :c)))
⇒ (2 b :b)

File: dash.info, Node: List to list, Next: Reductions, Prev: Sublist selection, Up: Functions
2.3 List to list
================
Functions returning a modified copy of the input list.
-- Function: -keep (fn list)
Return a new list of the non-‘nil’ results of applying FN to each
item in LIST. Like ‘-filter’ (*note -filter::), but returns the
non-‘nil’ results of FN instead of the corresponding elements of
LIST.
Its anaphoric counterpart is ‘--keep’.
(-keep #'cdr '((1 2 3) (4 5) (6)))
⇒ ((2 3) (5))
(-keep (lambda (n) (and (> n 3) (* 10 n))) '(1 2 3 4 5 6))
⇒ (40 50 60)
(--keep (and (> it 3) (* 10 it)) '(1 2 3 4 5 6))
⇒ (40 50 60)
-- Function: -concat (&rest sequences)
Concatenate all the arguments and make the result a list. The
result is a list whose elements are the elements of all the
arguments. Each argument may be a list, vector or string.
All arguments except the last argument are copied. The last
argument is just used as the tail of the new list.
(-concat '(1))
⇒ (1)
(-concat '(1) '(2))
⇒ (1 2)
(-concat '(1) '(2 3) '(4))
⇒ (1 2 3 4)
-- Function: -flatten (l)
Take a nested list L and return its contents as a single, flat
list.
Note that because ‘nil’ represents a list of zero elements (an
empty list), any mention of ‘nil’ in L will disappear after
flattening. If you need to preserve nils, consider ‘-flatten-n’
(*note -flatten-n::) or map them to some unique symbol and then map
them back.
Conses of two atoms are considered "terminals", that is, they
aren’t flattened further.
See also: ‘-flatten-n’ (*note -flatten-n::)
(-flatten '((1)))
⇒ (1)
(-flatten '((1 (2 3) (((4 (5)))))))
⇒ (1 2 3 4 5)
(-flatten '(1 2 (3 . 4)))
⇒ (1 2 (3 . 4))
-- Function: -flatten-n (num list)
Flatten NUM levels of a nested LIST.
See also: ‘-flatten’ (*note -flatten::)
(-flatten-n 1 '((1 2) ((3 4) ((5 6)))))
⇒ (1 2 (3 4) ((5 6)))
(-flatten-n 2 '((1 2) ((3 4) ((5 6)))))
⇒ (1 2 3 4 (5 6))
(-flatten-n 3 '((1 2) ((3 4) ((5 6)))))
⇒ (1 2 3 4 5 6)
-- Function: -replace (old new list)
Replace all OLD items in LIST with NEW.
Elements are compared using ‘equal’.
See also: ‘-replace-at’ (*note -replace-at::)
(-replace 1 "1" '(1 2 3 4 3 2 1))
⇒ ("1" 2 3 4 3 2 "1")
(-replace "foo" "bar" '("a" "nice" "foo" "sentence" "about" "foo"))
⇒ ("a" "nice" "bar" "sentence" "about" "bar")
(-replace 1 2 nil)
⇒ nil
-- Function: -replace-first (old new list)
Replace the first occurrence of OLD with NEW in LIST.
Elements are compared using ‘equal’.
See also: ‘-map-first’ (*note -map-first::)
(-replace-first 1 "1" '(1 2 3 4 3 2 1))
⇒ ("1" 2 3 4 3 2 1)
(-replace-first "foo" "bar" '("a" "nice" "foo" "sentence" "about" "foo"))
⇒ ("a" "nice" "bar" "sentence" "about" "foo")
(-replace-first 1 2 nil)
⇒ nil
-- Function: -replace-last (old new list)
Replace the last occurrence of OLD with NEW in LIST.
Elements are compared using ‘equal’.
See also: ‘-map-last’ (*note -map-last::)
(-replace-last 1 "1" '(1 2 3 4 3 2 1))
⇒ (1 2 3 4 3 2 "1")
(-replace-last "foo" "bar" '("a" "nice" "foo" "sentence" "about" "foo"))
⇒ ("a" "nice" "foo" "sentence" "about" "bar")
(-replace-last 1 2 nil)
⇒ nil
-- Function: -insert-at (n x list)
Return a list with X inserted into LIST at position N.
See also: ‘-splice’ (*note -splice::), ‘-splice-list’ (*note
-splice-list::)
(-insert-at 1 'x '(a b c))
⇒ (a x b c)
(-insert-at 12 'x '(a b c))
⇒ (a b c x)
-- Function: -replace-at (n x list)
Return a list with element at Nth position in LIST replaced with X.
See also: ‘-replace’ (*note -replace::)
(-replace-at 0 9 '(0 1 2 3 4 5))
⇒ (9 1 2 3 4 5)
(-replace-at 1 9 '(0 1 2 3 4 5))
⇒ (0 9 2 3 4 5)
(-replace-at 4 9 '(0 1 2 3 4 5))
⇒ (0 1 2 3 9 5)
-- Function: -update-at (n func list)
Use FUNC to update the Nth element of LIST. Return a copy of LIST
where the Nth element is replaced with the result of calling FUNC
on it.
See also: ‘-map-when’ (*note -map-when::)
(-update-at 0 (lambda (x) (+ x 9)) '(0 1 2 3 4 5))
⇒ (9 1 2 3 4 5)
(-update-at 1 (lambda (x) (+ x 8)) '(0 1 2 3 4 5))
⇒ (0 9 2 3 4 5)
(--update-at 2 (length it) '("foo" "bar" "baz" "quux"))
⇒ ("foo" "bar" 3 "quux")
-- Function: -remove-at (n list)
Return LIST with its element at index N removed. That is, remove
any element selected as (nth N LIST) from LIST and return the
result.
This is a non-destructive operation: parts of LIST (but not
necessarily all of it) are copied as needed to avoid destructively
modifying it.
See also: ‘-remove-at-indices’ (*note -remove-at-indices::),
‘-remove’ (*note -remove::).
(-remove-at 0 '(a b c))
⇒ (b c)
(-remove-at 1 '(a b c))
⇒ (a c)
(-remove-at 2 '(a b c))
⇒ (a b)
-- Function: -remove-at-indices (indices list)
Return LIST with its elements at INDICES removed. That is, for
each index I in INDICES, remove any element selected as (nth I
LIST) from LIST.
This is a non-destructive operation: parts of LIST (but not
necessarily all of it) are copied as needed to avoid destructively
modifying it.
See also: ‘-remove-at’ (*note -remove-at::), ‘-remove’ (*note
-remove::).
(-remove-at-indices '(0) '(a b c d e))
⇒ (b c d e)
(-remove-at-indices '(1 3) '(a b c d e))
⇒ (a c e)
(-remove-at-indices '(4 0 2) '(a b c d e))
⇒ (b d)

File: dash.info, Node: Reductions, Next: Unfolding, Prev: List to list, Up: Functions
2.4 Reductions
==============
Functions reducing lists to a single value (which may also be a list).
-- Function: -reduce-from (fn init list)
Reduce the function FN across LIST, starting with INIT. Return the
result of applying FN to INIT and the first element of LIST, then
applying FN to that result and the second element, etc. If LIST is
empty, return INIT without calling FN.
This function’s anaphoric counterpart is ‘--reduce-from’.
For other folds, see also ‘-reduce’ (*note -reduce::) and
‘-reduce-r’ (*note -reduce-r::).
(-reduce-from #'- 10 '(1 2 3))
⇒ 4
(-reduce-from #'list 10 '(1 2 3))
⇒ (((10 1) 2) 3)
(--reduce-from (concat acc " " it) "START" '("a" "b" "c"))
⇒ "START a b c"
-- Function: -reduce-r-from (fn init list)
Reduce the function FN across LIST in reverse, starting with INIT.
Return the result of applying FN to the last element of LIST and
INIT, then applying FN to the second-to-last element and the
previous result of FN, etc. That is, the first argument of FN is
the current element, and its second argument the accumulated value.
If LIST is empty, return INIT without calling FN.
This function is like ‘-reduce-from’ (*note -reduce-from::) but the
operation associates from the right rather than left. In other
words, it starts from the end of LIST and flips the arguments to
FN. Conceptually, it is like replacing the conses in LIST with
applications of FN, and its last link with INIT, and evaluating the
resulting expression.
This function’s anaphoric counterpart is ‘--reduce-r-from’.
For other folds, see also ‘-reduce-r’ (*note -reduce-r::) and
‘-reduce’ (*note -reduce::).
(-reduce-r-from #'- 10 '(1 2 3))
⇒ -8
(-reduce-r-from #'list 10 '(1 2 3))
⇒ (1 (2 (3 10)))
(--reduce-r-from (concat it " " acc) "END" '("a" "b" "c"))
⇒ "a b c END"
-- Function: -reduce (fn list)
Reduce the function FN across LIST. Return the result of applying
FN to the first two elements of LIST, then applying FN to that
result and the third element, etc. If LIST contains a single
element, return it without calling FN. If LIST is empty, return
the result of calling FN with no arguments.
This function’s anaphoric counterpart is ‘--reduce’.
For other folds, see also ‘-reduce-from’ (*note -reduce-from::) and
‘-reduce-r’ (*note -reduce-r::).
(-reduce #'- '(1 2 3 4))
⇒ -8
(-reduce #'list '(1 2 3 4))
⇒ (((1 2) 3) 4)
(--reduce (format "%s-%d" acc it) '(1 2 3))
⇒ "1-2-3"
-- Function: -reduce-r (fn list)
Reduce the function FN across LIST in reverse. Return the result
of applying FN to the last two elements of LIST, then applying FN
to the third-to-last element and the previous result of FN, etc.
That is, the first argument of FN is the current element, and its
second argument the accumulated value. If LIST contains a single
element, return it without calling FN. If LIST is empty, return
the result of calling FN with no arguments.
This function is like ‘-reduce’ (*note -reduce::) but the operation
associates from the right rather than left. In other words, it
starts from the end of LIST and flips the arguments to FN.
Conceptually, it is like replacing the conses in LIST with
applications of FN, ignoring its last link, and evaluating the
resulting expression.
This function’s anaphoric counterpart is ‘--reduce-r’.
For other folds, see also ‘-reduce-r-from’ (*note -reduce-r-from::)
and ‘-reduce’ (*note -reduce::).
(-reduce-r #'- '(1 2 3 4))
⇒ -2
(-reduce-r #'list '(1 2 3 4))
⇒ (1 (2 (3 4)))
(--reduce-r (format "%s-%d" acc it) '(1 2 3))
⇒ "3-2-1"
-- Function: -reductions-from (fn init list)
Return a list of FN’s intermediate reductions across LIST. That
is, a list of the intermediate values of the accumulator when
‘-reduce-from’ (*note -reduce-from::) (which see) is called with
the same arguments.
This function’s anaphoric counterpart is ‘--reductions-from’.
For other folds, see also ‘-reductions’ (*note -reductions::) and
‘-reductions-r’ (*note -reductions-r::).
(-reductions-from #'max 0 '(2 1 4 3))
⇒ (0 2 2 4 4)
(-reductions-from #'* 1 '(1 2 3 4))
⇒ (1 1 2 6 24)
(--reductions-from (format "(FN %s %d)" acc it) "INIT" '(1 2 3))
⇒ ("INIT" "(FN INIT 1)" "(FN (FN INIT 1) 2)" "(FN (FN (FN INIT 1) 2) 3)")
-- Function: -reductions-r-from (fn init list)
Return a list of FN’s intermediate reductions across reversed LIST.
That is, a list of the intermediate values of the accumulator when
‘-reduce-r-from’ (*note -reduce-r-from::) (which see) is called
with the same arguments.
This function’s anaphoric counterpart is ‘--reductions-r-from’.
For other folds, see also ‘-reductions’ (*note -reductions::) and
‘-reductions-r’ (*note -reductions-r::).
(-reductions-r-from #'max 0 '(2 1 4 3))
⇒ (4 4 4 3 0)
(-reductions-r-from #'* 1 '(1 2 3 4))
⇒ (24 24 12 4 1)
(--reductions-r-from (format "(FN %d %s)" it acc) "INIT" '(1 2 3))
⇒ ("(FN 1 (FN 2 (FN 3 INIT)))" "(FN 2 (FN 3 INIT))" "(FN 3 INIT)" "INIT")
-- Function: -reductions (fn list)
Return a list of FN’s intermediate reductions across LIST. That
is, a list of the intermediate values of the accumulator when
‘-reduce’ (*note -reduce::) (which see) is called with the same
arguments.
This function’s anaphoric counterpart is ‘--reductions’.
For other folds, see also ‘-reductions’ (*note -reductions::) and
‘-reductions-r’ (*note -reductions-r::).
(-reductions #'+ '(1 2 3 4))
⇒ (1 3 6 10)
(-reductions #'* '(1 2 3 4))
⇒ (1 2 6 24)
(--reductions (format "(FN %s %d)" acc it) '(1 2 3))
⇒ (1 "(FN 1 2)" "(FN (FN 1 2) 3)")
-- Function: -reductions-r (fn list)
Return a list of FN’s intermediate reductions across reversed LIST.
That is, a list of the intermediate values of the accumulator when
‘-reduce-r’ (*note -reduce-r::) (which see) is called with the same
arguments.
This function’s anaphoric counterpart is ‘--reductions-r’.
For other folds, see also ‘-reductions-r-from’ (*note
-reductions-r-from::) and ‘-reductions’ (*note -reductions::).
(-reductions-r #'+ '(1 2 3 4))
⇒ (10 9 7 4)
(-reductions-r #'* '(1 2 3 4))
⇒ (24 24 12 4)
(--reductions-r (format "(FN %d %s)" it acc) '(1 2 3))
⇒ ("(FN 1 (FN 2 3))" "(FN 2 3)" 3)
-- Function: -count (pred list)
Counts the number of items in LIST where (PRED item) is non-‘nil’.
(-count 'even? '(1 2 3 4 5))
⇒ 2
(--count (< it 4) '(1 2 3 4))
⇒ 3
-- Function: -sum (list)
Return the sum of LIST.
(-sum ())
⇒ 0
(-sum '(1))
⇒ 1
(-sum '(1 2 3 4))
⇒ 10
-- Function: -running-sum (list)
Return a list with running sums of items in LIST. LIST must be
non-empty.
(-running-sum '(1 2 3 4))
⇒ (1 3 6 10)
(-running-sum '(1))
⇒ (1)
(-running-sum ())
error→ Wrong type argument: consp, nil
-- Function: -product (list)
Return the product of LIST.
(-product ())
⇒ 1
(-product '(1))
⇒ 1
(-product '(1 2 3 4))
⇒ 24
-- Function: -running-product (list)
Return a list with running products of items in LIST. LIST must be
non-empty.
(-running-product '(1 2 3 4))
⇒ (1 2 6 24)
(-running-product '(1))
⇒ (1)
(-running-product ())
error→ Wrong type argument: consp, nil
-- Function: -inits (list)
Return all prefixes of LIST.
(-inits '(1 2 3 4))
⇒ (nil (1) (1 2) (1 2 3) (1 2 3 4))
(-inits nil)
⇒ (nil)
(-inits '(1))
⇒ (nil (1))
-- Function: -tails (list)
Return all suffixes of LIST.
(-tails '(1 2 3 4))
⇒ ((1 2 3 4) (2 3 4) (3 4) (4) nil)
(-tails nil)
⇒ (nil)
(-tails '(1))
⇒ ((1) nil)
-- Function: -common-prefix (&rest lists)
Return the longest common prefix of LISTS.
(-common-prefix '(1))
⇒ (1)
(-common-prefix '(1 2) '(3 4) '(1 2))
⇒ ()
(-common-prefix '(1 2) '(1 2 3) '(1 2 3 4))
⇒ (1 2)
-- Function: -common-suffix (&rest lists)
Return the longest common suffix of LISTS.
(-common-suffix '(1))
⇒ (1)
(-common-suffix '(1 2) '(3 4) '(1 2))
⇒ ()
(-common-suffix '(1 2 3 4) '(2 3 4) '(3 4))
⇒ (3 4)
-- Function: -min (list)
Return the smallest value from LIST of numbers or markers.
(-min '(0))
⇒ 0
(-min '(3 2 1))
⇒ 1
(-min '(1 2 3))
⇒ 1
-- Function: -min-by (comparator list)
Take a comparison function COMPARATOR and a LIST and return the
least element of the list by the comparison function.
See also combinator ‘-on’ (*note -on::) which can transform the
values before comparing them.
(-min-by '> '(4 3 6 1))
⇒ 1
(--min-by (> (car it) (car other)) '((1 2 3) (2) (3 2)))
⇒ (1 2 3)
(--min-by (> (length it) (length other)) '((1 2 3) (2) (3 2)))
⇒ (2)
-- Function: -max (list)
Return the largest value from LIST of numbers or markers.
(-max '(0))
⇒ 0
(-max '(3 2 1))
⇒ 3
(-max '(1 2 3))
⇒ 3
-- Function: -max-by (comparator list)
Take a comparison function COMPARATOR and a LIST and return the
greatest element of the list by the comparison function.
See also combinator ‘-on’ (*note -on::) which can transform the
values before comparing them.
(-max-by '> '(4 3 6 1))
⇒ 6
(--max-by (> (car it) (car other)) '((1 2 3) (2) (3 2)))
⇒ (3 2)
(--max-by (> (length it) (length other)) '((1 2 3) (2) (3 2)))
⇒ (1 2 3)
-- Function: -frequencies (list)
Count the occurrences of each distinct element of LIST.
Return an alist of (ELEMENT . N), where each ELEMENT occurs N
times in LIST.
The test for equality is done with ‘equal’, or with ‘-compare-fn’
if that is non-‘nil’.
See also ‘-count’ (*note -count::) and ‘-group-by’ (*note
-group-by::).
(-frequencies ())
⇒ ()
(-frequencies '(1 2 3 1 2 1))
⇒ ((1 . 3) (2 . 2) (3 . 1))
(let ((-compare-fn #'string=)) (-frequencies '(a "a")))
⇒ ((a . 2))

File: dash.info, Node: Unfolding, Next: Predicates, Prev: Reductions, Up: Functions
2.5 Unfolding
=============
Operations dual to reductions, building lists from a seed value rather
than consuming a list to produce a single value.
-- Function: -iterate (fun init n)
Return a list of iterated applications of FUN to INIT.
This means a list of the form:
(INIT (FUN INIT) (FUN (FUN INIT)) ...)
N is the length of the returned list.
(-iterate #'1+ 1 10)
⇒ (1 2 3 4 5 6 7 8 9 10)
(-iterate (lambda (x) (+ x x)) 2 5)
⇒ (2 4 8 16 32)
(--iterate (* it it) 2 5)
⇒ (2 4 16 256 65536)
-- Function: -unfold (fun seed)
Build a list from SEED using FUN.
This is "dual" operation to ‘-reduce-r’ (*note -reduce-r::): while
-reduce-r consumes a list to produce a single value, ‘-unfold’
(*note -unfold::) takes a seed value and builds a (potentially
infinite!) list.
FUN should return ‘nil’ to stop the generating process, or a cons
(A . B), where A will be prepended to the result and B is the new
seed.
(-unfold (lambda (x) (unless (= x 0) (cons x (1- x)))) 10)
⇒ (10 9 8 7 6 5 4 3 2 1)
(--unfold (when it (cons it (cdr it))) '(1 2 3 4))
⇒ ((1 2 3 4) (2 3 4) (3 4) (4))
(--unfold (when it (cons it (butlast it))) '(1 2 3 4))
⇒ ((1 2 3 4) (1 2 3) (1 2) (1))
-- Function: -repeat (n x)
Return a new list of length N with each element being X. Return
‘nil’ if N is less than 1.
(-repeat 3 :a)
⇒ (:a :a :a)
(-repeat 1 :a)
⇒ (:a)
(-repeat 0 :a)
⇒ ()
-- Function: -cycle (list)
Return an infinite circular copy of LIST. The returned list cycles
through the elements of LIST and repeats from the beginning.
(-take 5 (-cycle '(1 2 3)))
⇒ (1 2 3 1 2)
(-take 7 (-cycle '(1 "and" 3)))
⇒ (1 "and" 3 1 "and" 3 1)
(-zip-lists (-cycle '(3)) '(1 2))
⇒ ((3 1) (3 2))

File: dash.info, Node: Predicates, Next: Partitioning, Prev: Unfolding, Up: Functions
2.6 Predicates
==============
Reductions of one or more lists to a boolean value.
-- Function: -some (pred list)
Return (PRED x) for the first LIST item where (PRED x) is
non-‘nil’, else ‘nil’.
Alias: ‘-any’.
This function’s anaphoric counterpart is ‘--some’.
(-some #'stringp '(1 "2" 3))
⇒ t
(--some (string-match-p "x" it) '("foo" "axe" "xor"))
⇒ 1
(--some (= it-index 3) '(0 1 2))
⇒ nil
-- Function: -every (pred list)
Return non-‘nil’ if PRED returns non-‘nil’ for all items in LIST.
If so, return the last such result of PRED. Otherwise, once an
item is reached for which PRED returns ‘nil’, return ‘nil’ without
calling PRED on any further LIST elements.
This function is like ‘-every-p’, but on success returns the last
non-‘nil’ result of PRED instead of just ‘t’.
This function’s anaphoric counterpart is ‘--every’.
(-every #'numberp '(1 2 3))
⇒ t
(--every (string-match-p "x" it) '("axe" "xor"))
⇒ 0
(--every (= it it-index) '(0 1 3))
⇒ nil
-- Function: -any? (pred list)
Return ‘t’ if (PRED X) is non-‘nil’ for any X in LIST, else ‘nil’.
Alias: ‘-any-p’, ‘-some?’, ‘-some-p’
(-any? #'numberp '(nil 0 t))
⇒ t
(-any? #'numberp '(nil t t))
⇒ nil
(-any? #'null '(1 3 5))
⇒ nil
-- Function: -all? (pred list)
Return ‘t’ if (PRED X) is non-‘nil’ for all X in LIST, else ‘nil’.
In the latter case, stop after the first X for which (PRED X) is
‘nil’, without calling PRED on any subsequent elements of LIST.
The similar function ‘-every’ (*note -every::) is more widely
useful, since it returns the last non-‘nil’ result of PRED instead
of just ‘t’ on success.
Alias: ‘-all-p’, ‘-every-p’, ‘-every?’.
This function’s anaphoric counterpart is ‘--all?’.
(-all? #'numberp '(1 2 3))
⇒ t
(-all? #'numberp '(2 t 6))
⇒ nil
(--all? (= 0 (% it 2)) '(2 4 6))
⇒ t
-- Function: -none? (pred list)
Return ‘t’ if (PRED X) is ‘nil’ for all X in LIST, else ‘nil’.
Alias: ‘-none-p’
(-none? 'even? '(1 2 3))
⇒ nil
(-none? 'even? '(1 3 5))
⇒ t
(--none? (= 0 (% it 2)) '(1 2 3))
⇒ nil
-- Function: -only-some? (pred list)
Return ‘t’ if different LIST items both satisfy and do not satisfy
PRED. That is, if PRED returns both ‘nil’ for at least one item,
and non-‘nil’ for at least one other item in LIST. Return ‘nil’ if
all items satisfy the predicate or none of them do.
Alias: ‘-only-some-p’
(-only-some? 'even? '(1 2 3))
⇒ t
(-only-some? 'even? '(1 3 5))
⇒ nil
(-only-some? 'even? '(2 4 6))
⇒ nil
-- Function: -contains? (list element)
Return non-‘nil’ if LIST contains ELEMENT.
The test for equality is done with ‘equal’, or with ‘-compare-fn’
if that is non-‘nil’. As with ‘member’, the return value is
actually the tail of LIST whose car is ELEMENT.
Alias: ‘-contains-p’.
(-contains? '(1 2 3) 1)
⇒ (1 2 3)
(-contains? '(1 2 3) 2)
⇒ (2 3)
(-contains? '(1 2 3) 4)
⇒ ()
-- Function: -is-prefix? (prefix list)
Return non-‘nil’ if PREFIX is a prefix of LIST.
Alias: ‘-is-prefix-p’.
(-is-prefix? '(1 2 3) '(1 2 3 4 5))
⇒ t
(-is-prefix? '(1 2 3 4 5) '(1 2 3))
⇒ nil
(-is-prefix? '(1 3) '(1 2 3 4 5))
⇒ nil
-- Function: -is-suffix? (suffix list)
Return non-‘nil’ if SUFFIX is a suffix of LIST.
Alias: ‘-is-suffix-p’.
(-is-suffix? '(3 4 5) '(1 2 3 4 5))
⇒ t
(-is-suffix? '(1 2 3 4 5) '(3 4 5))
⇒ nil
(-is-suffix? '(3 5) '(1 2 3 4 5))
⇒ nil
-- Function: -is-infix? (infix list)
Return non-‘nil’ if INFIX is infix of LIST.
This operation runs in O(n^2) time
Alias: ‘-is-infix-p’
(-is-infix? '(1 2 3) '(1 2 3 4 5))
⇒ t
(-is-infix? '(2 3 4) '(1 2 3 4 5))
⇒ t
(-is-infix? '(3 4 5) '(1 2 3 4 5))
⇒ t
-- Function: -cons-pair? (obj)
Return non-‘nil’ if OBJ is a true cons pair. That is, a cons (A .
B) where B is not a list.
Alias: ‘-cons-pair-p’.
(-cons-pair? '(1 . 2))
⇒ t
(-cons-pair? '(1 2))
⇒ nil
(-cons-pair? '(1))
⇒ nil

File: dash.info, Node: Partitioning, Next: Indexing, Prev: Predicates, Up: Functions
2.7 Partitioning
================
Functions partitioning the input list into a list of lists.
-- Function: -split-at (n list)
Split LIST into two sublists after the Nth element. The result is
a list of two elements (TAKE DROP) where TAKE is a new list of the
first N elements of LIST, and DROP is the remaining elements of
LIST (not a copy). TAKE and DROP are like the results of ‘-take’
(*note -take::) and ‘-drop’ (*note -drop::), respectively, but the
split is done in a single list traversal.
(-split-at 3 '(1 2 3 4 5))
⇒ ((1 2 3) (4 5))
(-split-at 17 '(1 2 3 4 5))
⇒ ((1 2 3 4 5) nil)
(-split-at 0 '(1 2 3 4 5))
⇒ (nil (1 2 3 4 5))
-- Function: -split-with (pred list)
Split LIST into a prefix satisfying PRED, and the rest. The first
sublist is the prefix of LIST with successive elements satisfying
PRED, and the second sublist is the remaining elements that do not.
The result is like performing
((-take-while PRED LIST) (-drop-while PRED LIST))
but in no more than a single pass through LIST.
(-split-with 'even? '(1 2 3 4))
⇒ (nil (1 2 3 4))
(-split-with 'even? '(2 4 5 6))
⇒ ((2 4) (5 6))
(--split-with (< it 4) '(1 2 3 4 3 2 1))
⇒ ((1 2 3) (4 3 2 1))
-- Macro: -split-on (item list)
Split the LIST each time ITEM is found.
Unlike ‘-partition-by’ (*note -partition-by::), the ITEM is
discarded from the results. Empty lists are also removed from the
result.
Comparison is done by ‘equal’.
See also ‘-split-when’ (*note -split-when::)
(-split-on '| '(Nil | Leaf a | Node [Tree a]))
⇒ ((Nil) (Leaf a) (Node [Tree a]))
(-split-on :endgroup '("a" "b" :endgroup "c" :endgroup "d" "e"))
⇒ (("a" "b") ("c") ("d" "e"))
(-split-on :endgroup '("a" "b" :endgroup :endgroup "d" "e"))
⇒ (("a" "b") ("d" "e"))
-- Function: -split-when (fn list)
Split the LIST on each element where FN returns non-‘nil’.
Unlike ‘-partition-by’ (*note -partition-by::), the "matched"
element is discarded from the results. Empty lists are also
removed from the result.
This function can be thought of as a generalization of
‘split-string’.
(-split-when 'even? '(1 2 3 4 5 6))
⇒ ((1) (3) (5))
(-split-when 'even? '(1 2 3 4 6 8 9))
⇒ ((1) (3) (9))
(--split-when (memq it '(&optional &rest)) '(a b &optional c d &rest args))
⇒ ((a b) (c d) (args))
-- Function: -separate (pred list)
Split LIST into two sublists based on whether items satisfy PRED.
The result is like performing
((-filter PRED LIST) (-remove PRED LIST))
but in a single pass through LIST.
(-separate (lambda (num) (= 0 (% num 2))) '(1 2 3 4 5 6 7))
⇒ ((2 4 6) (1 3 5 7))
(--separate (< it 5) '(3 7 5 9 3 2 1 4 6))
⇒ ((3 3 2 1 4) (7 5 9 6))
(-separate 'cdr '((1 2) (1) (1 2 3) (4)))
⇒ (((1 2) (1 2 3)) ((1) (4)))
-- Function: -partition (n list)
Return a new list with the items in LIST grouped into N-sized
sublists. If there are not enough items to make the last group
N-sized, those items are discarded.
(-partition 2 '(1 2 3 4 5 6))
⇒ ((1 2) (3 4) (5 6))
(-partition 2 '(1 2 3 4 5 6 7))
⇒ ((1 2) (3 4) (5 6))
(-partition 3 '(1 2 3 4 5 6 7))
⇒ ((1 2 3) (4 5 6))
-- Function: -partition-all (n list)
Return a new list with the items in LIST grouped into N-sized
sublists. The last group may contain less than N items.
(-partition-all 2 '(1 2 3 4 5 6))
⇒ ((1 2) (3 4) (5 6))
(-partition-all 2 '(1 2 3 4 5 6 7))
⇒ ((1 2) (3 4) (5 6) (7))
(-partition-all 3 '(1 2 3 4 5 6 7))
⇒ ((1 2 3) (4 5 6) (7))
-- Function: -partition-in-steps (n step list)
Partition LIST into sublists of length N that are STEP items apart.
Like ‘-partition-all-in-steps’ (*note -partition-all-in-steps::),
but if there are not enough items to make the last group N-sized,
those items are discarded.
(-partition-in-steps 2 1 '(1 2 3 4))
⇒ ((1 2) (2 3) (3 4))
(-partition-in-steps 3 2 '(1 2 3 4))
⇒ ((1 2 3))
(-partition-in-steps 3 2 '(1 2 3 4 5))
⇒ ((1 2 3) (3 4 5))
-- Function: -partition-all-in-steps (n step list)
Partition LIST into sublists of length N that are STEP items apart.
Adjacent groups may overlap if N exceeds the STEP stride. Trailing
groups may contain less than N items.
(-partition-all-in-steps 2 1 '(1 2 3 4))
⇒ ((1 2) (2 3) (3 4) (4))
(-partition-all-in-steps 3 2 '(1 2 3 4))
⇒ ((1 2 3) (3 4))
(-partition-all-in-steps 3 2 '(1 2 3 4 5))
⇒ ((1 2 3) (3 4 5) (5))
-- Function: -partition-by (fn list)
Apply FN to each item in LIST, splitting it each time FN returns a
new value.
(-partition-by 'even? ())
⇒ ()
(-partition-by 'even? '(1 1 2 2 2 3 4 6 8))
⇒ ((1 1) (2 2 2) (3) (4 6 8))
(--partition-by (< it 3) '(1 2 3 4 3 2 1))
⇒ ((1 2) (3 4 3) (2 1))
-- Function: -partition-by-header (fn list)
Apply FN to the first item in LIST. That is the header value.
Apply FN to each item in LIST, splitting it each time FN returns
the header value, but only after seeing at least one other value
(the body).
(--partition-by-header (= it 1) '(1 2 3 1 2 1 2 3 4))
⇒ ((1 2 3) (1 2) (1 2 3 4))
(--partition-by-header (> it 0) '(1 2 0 1 0 1 2 3 0))
⇒ ((1 2 0) (1 0) (1 2 3 0))
(-partition-by-header 'even? '(2 1 1 1 4 1 3 5 6 6 1))
⇒ ((2 1 1 1) (4 1 3 5) (6 6 1))
-- Function: -partition-after-pred (pred list)
Partition LIST after each element for which PRED returns non-‘nil’.
This function’s anaphoric counterpart is ‘--partition-after-pred’.
(-partition-after-pred #'booleanp ())
⇒ ()
(-partition-after-pred #'booleanp '(t t))
⇒ ((t) (t))
(-partition-after-pred #'booleanp '(0 0 t t 0 t))
⇒ ((0 0 t) (t) (0 t))
-- Function: -partition-before-pred (pred list)
Partition directly before each time PRED is true on an element of
LIST.
(-partition-before-pred #'booleanp ())
⇒ ()
(-partition-before-pred #'booleanp '(0 t))
⇒ ((0) (t))
(-partition-before-pred #'booleanp '(0 0 t 0 t t))
⇒ ((0 0) (t 0) (t) (t))
-- Function: -partition-before-item (item list)
Partition directly before each time ITEM appears in LIST.
(-partition-before-item 3 ())
⇒ ()
(-partition-before-item 3 '(1))
⇒ ((1))
(-partition-before-item 3 '(3))
⇒ ((3))
-- Function: -partition-after-item (item list)
Partition directly after each time ITEM appears in LIST.
(-partition-after-item 3 ())
⇒ ()
(-partition-after-item 3 '(1))
⇒ ((1))
(-partition-after-item 3 '(3))
⇒ ((3))
-- Function: -group-by (fn list)
Separate LIST into an alist whose keys are FN applied to the
elements of LIST. Keys are compared by ‘equal’.
(-group-by 'even? ())
⇒ ()
(-group-by 'even? '(1 1 2 2 2 3 4 6 8))
⇒ ((nil 1 1 3) (t 2 2 2 4 6 8))
(--group-by (car (split-string it "/")) '("a/b" "c/d" "a/e"))
⇒ (("a" "a/b" "a/e") ("c" "c/d"))

File: dash.info, Node: Indexing, Next: Set operations, Prev: Partitioning, Up: Functions
2.8 Indexing
============
Functions retrieving or sorting based on list indices and related
predicates.
-- Function: -elem-index (elem list)
Return the first index of ELEM in LIST. That is, the index within
LIST of the first element that is ‘equal’ to ELEM. Return ‘nil’ if
there is no such element.
See also: ‘-find-index’ (*note -find-index::).
(-elem-index 2 '(6 7 8 3 4))
⇒ nil
(-elem-index "bar" '("foo" "bar" "baz"))
⇒ 1
(-elem-index '(1 2) '((3) (5 6) (1 2) nil))
⇒ 2
-- Function: -elem-indices (elem list)
Return the list of indices at which ELEM appears in LIST. That is,
the indices of all elements of LIST ‘equal’ to ELEM, in the same
ascending order as they appear in LIST.
(-elem-indices 2 '(6 7 8 3 4 1))
⇒ ()
(-elem-indices "bar" '("foo" "bar" "baz"))
⇒ (1)
(-elem-indices '(1 2) '((3) (1 2) (5 6) (1 2) nil))
⇒ (1 3)
-- Function: -find-index (pred list)
Return the index of the first item satisfying PRED in LIST. Return
‘nil’ if no such item is found.
PRED is called with one argument, the current list element, until
it returns non-‘nil’, at which point the search terminates.
This function’s anaphoric counterpart is ‘--find-index’.
See also: ‘-first’ (*note -first::), ‘-find-last-index’ (*note
-find-last-index::).
(-find-index #'numberp '(a b c))
⇒ nil
(-find-index #'natnump '(1 0 -1))
⇒ 0
(--find-index (> it 5) '(2 4 1 6 3 3 5 8))
⇒ 3
-- Function: -find-last-index (pred list)
Return the index of the last item satisfying PRED in LIST. Return
‘nil’ if no such item is found.
Predicate PRED is called with one argument each time, namely the
current list element.
This function’s anaphoric counterpart is ‘--find-last-index’.
See also: ‘-last’ (*note -last::), ‘-find-index’ (*note
-find-index::).
(-find-last-index #'numberp '(a b c))
⇒ nil
(--find-last-index (> it 5) '(2 7 1 6 3 8 5 2))
⇒ 5
(-find-last-index (-partial #'string< 'a) '(c b a))
⇒ 1
-- Function: -find-indices (pred list)
Return the list of indices in LIST satisfying PRED.
Each element of LIST in turn is passed to PRED. If the result is
non-‘nil’, the index of that element in LIST is included in the
result. The returned indices are in ascending order, i.e., in the
same order as they appear in LIST.
This function’s anaphoric counterpart is ‘--find-indices’.
See also: ‘-find-index’ (*note -find-index::), ‘-elem-indices’
(*note -elem-indices::).
(-find-indices #'numberp '(a b c))
⇒ ()
(-find-indices #'numberp '(8 1 d 2 b c a 3))
⇒ (0 1 3 7)
(--find-indices (> it 5) '(2 4 1 6 3 3 5 8))
⇒ (3 7)
-- Function: -grade-up (comparator list)
Grade elements of LIST using COMPARATOR relation. This yields a
permutation vector such that applying this permutation to LIST
sorts it in ascending order.
(-grade-up #'< '(3 1 4 2 1 3 3))
⇒ (1 4 3 0 5 6 2)
(let ((l '(3 1 4 2 1 3 3))) (-select-by-indices (-grade-up #'< l) l))
⇒ (1 1 2 3 3 3 4)
-- Function: -grade-down (comparator list)
Grade elements of LIST using COMPARATOR relation. This yields a
permutation vector such that applying this permutation to LIST
sorts it in descending order.
(-grade-down #'< '(3 1 4 2 1 3 3))
⇒ (2 0 5 6 3 1 4)
(let ((l '(3 1 4 2 1 3 3))) (-select-by-indices (-grade-down #'< l) l))
⇒ (4 3 3 3 2 1 1)

File: dash.info, Node: Set operations, Next: Other list operations, Prev: Indexing, Up: Functions
2.9 Set operations
==================
Operations pretending lists are sets.
-- Function: -union (list1 list2)
Return a new list of distinct elements appearing in either LIST1 or
LIST2.
The test for equality is done with ‘equal’, or with ‘-compare-fn’
if that is non-‘nil’.
(-union '(1 2 3) '(3 4 5))
⇒ (1 2 3 4 5)
(-union '(1 2 2 4) ())
⇒ (1 2 4)
(-union '(1 1 2 2) '(4 4 3 2 1))
⇒ (1 2 4 3)
-- Function: -difference (list1 list2)
Return a new list with the distinct members of LIST1 that are not
in LIST2.
The test for equality is done with ‘equal’, or with ‘-compare-fn’
if that is non-‘nil’.
(-difference () ())
⇒ ()
(-difference '(1 2 3) '(4 5 6))
⇒ (1 2 3)
(-difference '(1 2 3 4) '(3 4 5 6))
⇒ (1 2)
-- Function: -intersection (list1 list2)
Return a new list of distinct elements appearing in both LIST1 and
LIST2.
The test for equality is done with ‘equal’, or with ‘-compare-fn’
if that is non-‘nil’.
(-intersection () ())
⇒ ()
(-intersection '(1 2 3) '(4 5 6))
⇒ ()
(-intersection '(1 2 2 3) '(4 3 3 2))
⇒ (2 3)
-- Function: -powerset (list)
Return the power set of LIST.
(-powerset ())
⇒ (nil)
(-powerset '(x y))
⇒ ((x y) (x) (y) nil)
(-powerset '(x y z))
⇒ ((x y z) (x y) (x z) (x) (y z) (y) (z) nil)
-- Function: -permutations (list)
Return the distinct permutations of LIST.
Duplicate elements of LIST are determined by ‘equal’, or by
‘-compare-fn’ if that is non-‘nil’.
(-permutations ())
⇒ (nil)
(-permutations '(a a b))
⇒ ((a a b) (a b a) (b a a))
(-permutations '(a b c))
⇒ ((a b c) (a c b) (b a c) (b c a) (c a b) (c b a))
-- Function: -distinct (list)
Return a copy of LIST with all duplicate elements removed.
The test for equality is done with ‘equal’, or with ‘-compare-fn’
if that is non-‘nil’.
Alias: ‘-uniq’.
(-distinct ())
⇒ ()
(-distinct '(1 1 2 3 3))
⇒ (1 2 3)
(-distinct '(t t t))
⇒ (t)
-- Function: -same-items? (list1 list2)
Return non-‘nil’ if LIST1 and LIST2 have the same distinct
elements.
The order of the elements in the lists does not matter. The lists
may be of different lengths, i.e., contain duplicate elements. The
test for equality is done with ‘equal’, or with ‘-compare-fn’ if
that is non-‘nil’.
Alias: ‘-same-items-p’.
(-same-items? '(1 2 3) '(1 2 3))
⇒ t
(-same-items? '(1 1 2 3) '(3 3 2 1))
⇒ t
(-same-items? '(1 2 3) '(1 2 3 4))
⇒ nil

File: dash.info, Node: Other list operations, Next: Tree operations, Prev: Set operations, Up: Functions
2.10 Other list operations
==========================
Other list functions not fit to be classified elsewhere.
-- Function: -rotate (n list)
Rotate LIST N places to the right (left if N is negative). The
time complexity is O(n).
(-rotate 3 '(1 2 3 4 5 6 7))
⇒ (5 6 7 1 2 3 4)
(-rotate -3 '(1 2 3 4 5 6 7))
⇒ (4 5 6 7 1 2 3)
(-rotate 16 '(1 2 3 4 5 6 7))
⇒ (6 7 1 2 3 4 5)
-- Function: -cons* (&rest args)
Make a new list from the elements of ARGS. The last 2 elements of
ARGS are used as the final cons of the result, so if the final
element of ARGS is not a list, the result is a dotted list. With
no ARGS, return ‘nil’.
(-cons* 1 2)
⇒ (1 . 2)
(-cons* 1 2 3)
⇒ (1 2 . 3)
(-cons* 1)
⇒ 1
-- Function: -snoc (list elem &rest elements)
Append ELEM to the end of the list.
This is like ‘cons’, but operates on the end of list.
If any ELEMENTS are given, append them to the list as well.
(-snoc '(1 2 3) 4)
⇒ (1 2 3 4)
(-snoc '(1 2 3) 4 5 6)
⇒ (1 2 3 4 5 6)
(-snoc '(1 2 3) '(4 5 6))
⇒ (1 2 3 (4 5 6))
-- Function: -interpose (sep list)
Return a new list of all elements in LIST separated by SEP.
(-interpose "-" ())
⇒ ()
(-interpose "-" '("a"))
⇒ ("a")
(-interpose "-" '("a" "b" "c"))
⇒ ("a" "-" "b" "-" "c")
-- Function: -interleave (&rest lists)
Return a new list of the first item in each list, then the second
etc.
(-interleave '(1 2) '("a" "b"))
⇒ (1 "a" 2 "b")
(-interleave '(1 2) '("a" "b") '("A" "B"))
⇒ (1 "a" "A" 2 "b" "B")
(-interleave '(1 2 3) '("a" "b"))
⇒ (1 "a" 2 "b")
-- Function: -iota (count &optional start step)
Return a list containing COUNT numbers. Starts from START and adds
STEP each time. The default START is zero, the default STEP is 1.
This function takes its name from the corresponding primitive in
the APL language.
(-iota 6)
⇒ (0 1 2 3 4 5)
(-iota 4 2.5 -2)
⇒ (2.5 0.5 -1.5 -3.5)
(-iota -1)
error→ Wrong type argument: natnump, -1
-- Function: -zip-with (fn list1 list2)
Zip LIST1 and LIST2 into a new list using the function FN. That
is, apply FN pairwise taking as first argument the next element of
LIST1 and as second argument the next element of LIST2 at the
corresponding position. The result is as long as the shorter list.
This function’s anaphoric counterpart is ‘--zip-with’.
For other zips, see also ‘-zip-lists’ (*note -zip-lists::) and
‘-zip-fill’ (*note -zip-fill::).
(-zip-with #'+ '(1 2 3 4) '(5 6 7))
⇒ (6 8 10)
(-zip-with #'cons '(1 2 3) '(4 5 6 7))
⇒ ((1 . 4) (2 . 5) (3 . 6))
(--zip-with (format "%s & %s" it other) '(Batman Jekyll) '(Robin Hyde))
⇒ ("Batman & Robin" "Jekyll & Hyde")
-- Function: -zip-pair (list1 list2)
Zip LIST1 and LIST2 together.
Make a pair with the head of each list, followed by a pair with the
second element of each list, and so on. The number of pairs
returned is equal to the length of the shorter input list.
See also: ‘-zip-lists’ (*note -zip-lists::).
(-zip-pair '(1 2 3 4) '(5 6 7))
⇒ ((1 . 5) (2 . 6) (3 . 7))
(-zip-pair '(1 2 3) '(4 5 6))
⇒ ((1 . 4) (2 . 5) (3 . 6))
(-zip-pair '(1 2) '(3))
⇒ ((1 . 3))
-- Function: -zip-lists (&rest lists)
Zip LISTS together.
Group the head of each list, followed by the second element of each
list, and so on. The number of returned groupings is equal to the
length of the shortest input list, and the length of each grouping
is equal to the number of input LISTS.
The return value is always a list of proper lists, in contrast to
‘-zip’ (*note -zip::) which returns a list of dotted pairs when
only two input LISTS are provided.
See also: ‘-zip-pair’ (*note -zip-pair::).
(-zip-lists '(1 2 3) '(4 5 6))
⇒ ((1 4) (2 5) (3 6))
(-zip-lists '(1 2 3) '(4 5 6 7))
⇒ ((1 4) (2 5) (3 6))
(-zip-lists '(1 2) '(3 4 5) '(6))
⇒ ((1 3 6))
-- Function: -zip-lists-fill (fill-value &rest lists)
Zip LISTS together, padding shorter lists with FILL-VALUE. This is
like ‘-zip-lists’ (*note -zip-lists::) (which see), except it
retains all elements at positions beyond the end of the shortest
list. The number of returned groupings is equal to the length of
the longest input list, and the length of each grouping is equal to
the number of input LISTS.
(-zip-lists-fill 0 '(1 2) '(3 4 5) '(6))
⇒ ((1 3 6) (2 4 0) (0 5 0))
(-zip-lists-fill 0 '(1 2) '(3 4) '(5 6))
⇒ ((1 3 5) (2 4 6))
(-zip-lists-fill 0 '(1 2 3) nil)
⇒ ((1 0) (2 0) (3 0))
-- Function: -zip (&rest lists)
Zip LISTS together.
Group the head of each list, followed by the second element of each
list, and so on. The number of returned groupings is equal to the
length of the shortest input list, and the number of items in each
grouping is equal to the number of input LISTS.
If only two LISTS are provided as arguments, return the groupings
as a list of dotted pairs. Otherwise, return the groupings as a
list of proper lists.
Since the return value changes form depending on the number of
arguments, it is generally recommended to use ‘-zip-lists’ (*note
-zip-lists::) instead, or ‘-zip-pair’ (*note -zip-pair::) if a list
of dotted pairs is desired.
See also: ‘-unzip’ (*note -unzip::).
(-zip '(1 2 3 4) '(5 6 7) '(8 9))
⇒ ((1 5 8) (2 6 9))
(-zip '(1 2 3) '(4 5 6) '(7 8 9))
⇒ ((1 4 7) (2 5 8) (3 6 9))
(-zip '(1 2 3))
⇒ ((1) (2) (3))
-- Function: -zip-fill (fill-value &rest lists)
Zip LISTS together, padding shorter lists with FILL-VALUE. This is
like ‘-zip’ (*note -zip::) (which see), except it retains all
elements at positions beyond the end of the shortest list. The
number of returned groupings is equal to the length of the longest
input list, and the length of each grouping is equal to the number
of input LISTS.
Since the return value changes form depending on the number of
arguments, it is generally recommended to use ‘-zip-lists-fill’
(*note -zip-lists-fill::) instead, unless a list of dotted pairs is
explicitly desired.
(-zip-fill 0 '(1 2 3) '(4 5))
⇒ ((1 . 4) (2 . 5) (3 . 0))
(-zip-fill 0 () '(1 2 3))
⇒ ((0 . 1) (0 . 2) (0 . 3))
(-zip-fill 0 '(1 2) '(3 4) '(5 6))
⇒ ((1 3 5) (2 4 6))
-- Function: -unzip-lists (lists)
Unzip LISTS.
This works just like ‘-zip-lists’ (*note -zip-lists::) (which see),
but takes a list of lists instead of a variable number of
arguments, such that
(-unzip-lists (-zip-lists ARGS...))
is identity (given that the lists comprising ARGS are of the same
length).
(-unzip-lists (-zip-lists '(1 2) '(3 4) '(5 6)))
⇒ ((1 2) (3 4) (5 6))
(-unzip-lists '((1 2 3) (4 5) (6 7) (8 9)))
⇒ ((1 4 6 8) (2 5 7 9))
(-unzip-lists '((1 2 3) (4 5 6)))
⇒ ((1 4) (2 5) (3 6))
-- Function: -unzip (lists)
Unzip LISTS.
This works just like ‘-zip’ (*note -zip::) (which see), but takes a
list of lists instead of a variable number of arguments, such that
(-unzip (-zip L1 L2 L3 ...))
is identity (given that the lists are of the same length, and that
‘-zip’ (*note -zip::) is not called with two arguments, because of
the caveat described in its docstring).
Note in particular that calling ‘-unzip’ (*note -unzip::) on a list
of two lists will return a list of dotted pairs.
Since the return value changes form depending on the number of
LISTS, it is generally recommended to use ‘-unzip-lists’ (*note
-unzip-lists::) instead.
(-unzip (-zip '(1 2) '(3 4) '(5 6)))
⇒ ((1 . 2) (3 . 4) (5 . 6))
(-unzip '((1 2 3) (4 5 6)))
⇒ ((1 . 4) (2 . 5) (3 . 6))
(-unzip '((1 2 3) (4 5) (6 7) (8 9)))
⇒ ((1 4 6 8) (2 5 7 9))
-- Function: -pad (fill-value &rest lists)
Pad each of LISTS with FILL-VALUE until they all have equal
lengths.
Ensure all LISTS are as long as the longest one by repeatedly
appending FILL-VALUE to the shorter lists, and return the resulting
LISTS.
(-pad 0 ())
⇒ (nil)
(-pad 0 '(1 2) '(3 4))
⇒ ((1 2) (3 4))
(-pad 0 '(1 2) '(3 4 5 6) '(7 8 9))
⇒ ((1 2 0 0) (3 4 5 6) (7 8 9 0))
-- Function: -table (fn &rest lists)
Compute outer product of LISTS using function FN.
The function FN should have the same arity as the number of
supplied lists.
The outer product is computed by applying fn to all possible
combinations created by taking one element from each list in order.
The dimension of the result is (length lists).
See also: ‘-table-flat’ (*note -table-flat::)
(-table '* '(1 2 3) '(1 2 3))
⇒ ((1 2 3) (2 4 6) (3 6 9))
(-table (lambda (a b) (-sum (-zip-with '* a b))) '((1 2) (3 4)) '((1 3) (2 4)))
⇒ ((7 15) (10 22))
(apply '-table 'list (-repeat 3 '(1 2)))
⇒ ((((1 1 1) (2 1 1)) ((1 2 1) (2 2 1))) (((1 1 2) (2 1 2)) ((1 2 2) (2 2 2))))
-- Function: -table-flat (fn &rest lists)
Compute flat outer product of LISTS using function FN.
The function FN should have the same arity as the number of
supplied lists.
The outer product is computed by applying fn to all possible
combinations created by taking one element from each list in order.
The results are flattened, ignoring the tensor structure of the
result. This is equivalent to calling:
(-flatten-n (1- (length lists)) (apply ’-table fn lists))
but the implementation here is much more efficient.
See also: ‘-flatten-n’ (*note -flatten-n::), ‘-table’ (*note
-table::)
(-table-flat 'list '(1 2 3) '(a b c))
⇒ ((1 a) (2 a) (3 a) (1 b) (2 b) (3 b) (1 c) (2 c) (3 c))
(-table-flat '* '(1 2 3) '(1 2 3))
⇒ (1 2 3 2 4 6 3 6 9)
(apply '-table-flat 'list (-repeat 3 '(1 2)))
⇒ ((1 1 1) (2 1 1) (1 2 1) (2 2 1) (1 1 2) (2 1 2) (1 2 2) (2 2 2))
-- Function: -first (pred list)
Return the first item in LIST for which PRED returns non-‘nil’.
Return ‘nil’ if no such element is found.
To get the first item in the list no questions asked, use
‘-first-item’ (*note -first-item::).
Alias: ‘-find’.
This function’s anaphoric counterpart is ‘--first’.
(-first #'natnump '(-1 0 1))
⇒ 0
(-first #'null '(1 2 3))
⇒ nil
(--first (> it 2) '(1 2 3))
⇒ 3
-- Function: -last (pred list)
Return the last x in LIST where (PRED x) is non-‘nil’, else ‘nil’.
(-last 'even? '(1 2 3 4 5 6 3 3 3))
⇒ 6
(-last 'even? '(1 3 7 5 9))
⇒ nil
(--last (> (length it) 3) '("a" "looong" "word" "and" "short" "one"))
⇒ "short"
-- Function: -first-item (list)
Return the first item of LIST, or ‘nil’ on an empty list.
See also: ‘-second-item’ (*note -second-item::), ‘-last-item’
(*note -last-item::), etc.
(-first-item ())
⇒ ()
(-first-item '(1 2 3 4 5))
⇒ 1
(let ((list (list 1 2 3))) (setf (-first-item list) 5) list)
⇒ (5 2 3)
-- Function: -second-item (list)
Return the second item of LIST, or ‘nil’ if LIST is too short.
See also: ‘-first-item’ (*note -first-item::), ‘-third-item’ (*note
-third-item::), etc.
(-second-item ())
⇒ ()
(-second-item '(1 2 3 4 5))
⇒ 2
(let ((list (list 1 2))) (setf (-second-item list) 5) list)
⇒ (1 5)
-- Function: -third-item (list)
Return the third item of LIST, or ‘nil’ if LIST is too short.
See also: ‘-second-item’ (*note -second-item::), ‘-fourth-item’
(*note -fourth-item::), etc.
(-third-item ())
⇒ ()
(-third-item '(1 2))
⇒ ()
(-third-item '(1 2 3 4 5))
⇒ 3
-- Function: -fourth-item (list)
Return the fourth item of LIST, or ‘nil’ if LIST is too short.
See also: ‘-third-item’ (*note -third-item::), ‘-fifth-item’ (*note
-fifth-item::), etc.
(-fourth-item ())
⇒ ()
(-fourth-item '(1 2 3))
⇒ ()
(-fourth-item '(1 2 3 4 5))
⇒ 4
-- Function: -fifth-item (list)
Return the fifth item of LIST, or ‘nil’ if LIST is too short.
See also: ‘-fourth-item’ (*note -fourth-item::), ‘-last-item’
(*note -last-item::), etc.
(-fifth-item ())
⇒ ()
(-fifth-item '(1 2 3 4))
⇒ ()
(-fifth-item '(1 2 3 4 5))
⇒ 5
-- Function: -last-item (list)
Return the last item of LIST, or ‘nil’ on an empty list.
See also: ‘-first-item’ (*note -first-item::), etc.
(-last-item ())
⇒ ()
(-last-item '(1 2 3 4 5))
⇒ 5
(let ((list (list 1 2 3))) (setf (-last-item list) 5) list)
⇒ (1 2 5)
-- Function: -butlast (list)
Return a list of all items in list except for the last.
(-butlast '(1 2 3))
⇒ (1 2)
(-butlast '(1 2))
⇒ (1)
(-butlast '(1))
⇒ nil
-- Function: -sort (comparator list)
Sort LIST, stably, comparing elements using COMPARATOR. Return the
sorted list. LIST is NOT modified by side effects. COMPARATOR is
called with two elements of LIST, and should return non-‘nil’ if
the first element should sort before the second.
(-sort #'< '(3 1 2))
⇒ (1 2 3)
(-sort #'> '(3 1 2))
⇒ (3 2 1)
(--sort (< it other) '(3 1 2))
⇒ (1 2 3)
-- Function: -list (arg)
Ensure ARG is a list. If ARG is already a list, return it as is
(not a copy). Otherwise, return a new list with ARG as its only
element.
Another supported calling convention is (-list &rest ARGS). In
this case, if ARG is not a list, a new list with all of ARGS as
elements is returned. This use is supported for backward
compatibility and is otherwise deprecated.
(-list 1)
⇒ (1)
(-list ())
⇒ ()
(-list '(1 2 3))
⇒ (1 2 3)
-- Function: -fix (fn list)
Compute the (least) fixpoint of FN with initial input LIST.
FN is called at least once, results are compared with ‘equal’.
(-fix (lambda (l) (-non-nil (--mapcat (-split-at (/ (length it) 2) it) l))) '((1 2 3)))
⇒ ((1) (2) (3))
(let ((l '((starwars scifi) (jedi starwars warrior)))) (--fix (-uniq (--mapcat (cons it (cdr (assq it l))) it)) '(jedi book)))
⇒ (jedi starwars warrior scifi book)

File: dash.info, Node: Tree operations, Next: Threading macros, Prev: Other list operations, Up: Functions
2.11 Tree operations
====================
Functions pretending lists are trees.
-- Function: -tree-seq (branch children tree)
Return a sequence of the nodes in TREE, in depth-first search
order.
BRANCH is a predicate of one argument that returns non-‘nil’ if the
passed argument is a branch, that is, a node that can have
children.
CHILDREN is a function of one argument that returns the children of
the passed branch node.
Non-branch nodes are simply copied.
(-tree-seq 'listp 'identity '(1 (2 3) 4 (5 (6 7))))
⇒ ((1 (2 3) 4 (5 (6 7))) 1 (2 3) 2 3 4 (5 (6 7)) 5 (6 7) 6 7)
(-tree-seq 'listp 'reverse '(1 (2 3) 4 (5 (6 7))))
⇒ ((1 (2 3) 4 (5 (6 7))) (5 (6 7)) (6 7) 7 6 5 4 (2 3) 3 2 1)
(--tree-seq (vectorp it) (append it nil) [1 [2 3] 4 [5 [6 7]]])
⇒ ([1 [2 3] 4 [5 [6 7]]] 1 [2 3] 2 3 4 [5 [6 7]] 5 [6 7] 6 7)
-- Function: -tree-map (fn tree)
Apply FN to each element of TREE while preserving the tree
structure.
(-tree-map '1+ '(1 (2 3) (4 (5 6) 7)))
⇒ (2 (3 4) (5 (6 7) 8))
(-tree-map '(lambda (x) (cons x (expt 2 x))) '(1 (2 3) 4))
⇒ ((1 . 2) ((2 . 4) (3 . 8)) (4 . 16))
(--tree-map (length it) '("<body>" ("<p>" "text" "</p>") "</body>"))
⇒ (6 (3 4 4) 7)
-- Function: -tree-map-nodes (pred fun tree)
Call FUN on each node of TREE that satisfies PRED.
If PRED returns ‘nil’, continue descending down this node. If PRED
returns non-‘nil’, apply FUN to this node and do not descend
further.
(-tree-map-nodes 'vectorp (lambda (x) (-sum (append x nil))) '(1 [2 3] 4 (5 [6 7] 8)))
⇒ (1 5 4 (5 13 8))
(-tree-map-nodes 'keywordp (lambda (x) (symbol-name x)) '(1 :foo 4 ((5 6 :bar) :baz 8)))
⇒ (1 ":foo" 4 ((5 6 ":bar") ":baz" 8))
(--tree-map-nodes (eq (car-safe it) 'add-mode) (-concat it (list :mode 'emacs-lisp-mode)) '(with-mode emacs-lisp-mode (foo bar) (add-mode a b) (baz (add-mode c d))))
⇒ (with-mode emacs-lisp-mode (foo bar) (add-mode a b :mode emacs-lisp-mode) (baz (add-mode c d :mode emacs-lisp-mode)))
-- Function: -tree-reduce (fn tree)
Use FN to reduce elements of list TREE. If elements of TREE are
lists themselves, apply the reduction recursively.
FN is first applied to first element of the list and second
element, then on this result and third element from the list etc.
See ‘-reduce-r’ (*note -reduce-r::) for how exactly are lists of
zero or one element handled.
(-tree-reduce '+ '(1 (2 3) (4 5)))
⇒ 15
(-tree-reduce 'concat '("strings" (" on" " various") ((" levels"))))
⇒ "strings on various levels"
(--tree-reduce (cond ((stringp it) (concat it " " acc)) (t (let ((sn (symbol-name it))) (concat "<" sn ">" acc "</" sn ">")))) '(body (p "some words") (div "more" (b "bold") "words")))
⇒ "<body><p>some words</p> <div>more <b>bold</b> words</div></body>"
-- Function: -tree-reduce-from (fn init-value tree)
Use FN to reduce elements of list TREE. If elements of TREE are
lists themselves, apply the reduction recursively.
FN is first applied to INIT-VALUE and first element of the list,
then on this result and second element from the list etc.
The initial value is ignored on cons pairs as they always contain
two elements.
(-tree-reduce-from '+ 1 '(1 (1 1) ((1))))
⇒ 8
(--tree-reduce-from (-concat acc (list it)) nil '(1 (2 3 (4 5)) (6 7)))
⇒ ((7 6) ((5 4) 3 2) 1)
-- Function: -tree-mapreduce (fn folder tree)
Apply FN to each element of TREE, and make a list of the results.
If elements of TREE are lists themselves, apply FN recursively to
elements of these nested lists.
Then reduce the resulting lists using FOLDER and initial value
INIT-VALUE. See ‘-reduce-r-from’ (*note -reduce-r-from::).
This is the same as calling ‘-tree-reduce’ (*note -tree-reduce::)
after ‘-tree-map’ (*note -tree-map::) but is twice as fast as it
only traverse the structure once.
(-tree-mapreduce 'list 'append '(1 (2 (3 4) (5 6)) (7 (8 9))))
⇒ (1 2 3 4 5 6 7 8 9)
(--tree-mapreduce 1 (+ it acc) '(1 (2 (4 9) (2 1)) (7 (4 3))))
⇒ 9
(--tree-mapreduce 0 (max acc (1+ it)) '(1 (2 (4 9) (2 1)) (7 (4 3))))
⇒ 3
-- Function: -tree-mapreduce-from (fn folder init-value tree)
Apply FN to each element of TREE, and make a list of the results.
If elements of TREE are lists themselves, apply FN recursively to
elements of these nested lists.
Then reduce the resulting lists using FOLDER and initial value
INIT-VALUE. See ‘-reduce-r-from’ (*note -reduce-r-from::).
This is the same as calling ‘-tree-reduce-from’ (*note
-tree-reduce-from::) after ‘-tree-map’ (*note -tree-map::) but is
twice as fast as it only traverse the structure once.
(-tree-mapreduce-from 'identity '* 1 '(1 (2 (3 4) (5 6)) (7 (8 9))))
⇒ 362880
(--tree-mapreduce-from (+ it it) (cons it acc) nil '(1 (2 (4 9) (2 1)) (7 (4 3))))
⇒ (2 (4 (8 18) (4 2)) (14 (8 6)))
(concat "{" (--tree-mapreduce-from (cond ((-cons-pair? it) (concat (symbol-name (car it)) " -> " (symbol-name (cdr it)))) (t (concat (symbol-name it) " : {"))) (concat it (unless (or (equal acc "}") (equal (substring it (1- (length it))) "{")) ", ") acc) "}" '((elisp-mode (foo (bar . booze)) (baz . qux)) (c-mode (foo . bla) (bum . bam)))))
⇒ "{elisp-mode : {foo : {bar -> booze}, baz -> qux}, c-mode : {foo -> bla, bum -> bam}}"
-- Function: -clone (list)
Create a deep copy of LIST. The new list has the same elements and
structure but all cons are replaced with new ones. This is useful
when you need to clone a structure such as plist or alist.
(let* ((a (list (list 1))) (b (-clone a))) (setcar (car a) 2) b)
⇒ ((1))

File: dash.info, Node: Threading macros, Next: Binding, Prev: Tree operations, Up: Functions
2.12 Threading macros
=====================
Macros that conditionally combine sequential forms for brevity or
readability.
-- Macro: -> (x &optional form &rest more)
Thread the expr through the forms. Insert X as the second item in
the first form, making a list of it if it is not a list already.
If there are more forms, insert the first form as the second item
in second form, etc.
(-> '(2 3 5))
⇒ (2 3 5)
(-> '(2 3 5) (append '(8 13)))
⇒ (2 3 5 8 13)
(-> '(2 3 5) (append '(8 13)) (-slice 1 -1))
⇒ (3 5 8)
-- Macro: ->> (x &optional form &rest more)
Thread the expr through the forms. Insert X as the last item in
the first form, making a list of it if it is not a list already.
If there are more forms, insert the first form as the last item in
second form, etc.
(->> '(1 2 3) (-map 'square))
⇒ (1 4 9)
(->> '(1 2 3) (-map 'square) (-remove 'even?))
⇒ (1 9)
(->> '(1 2 3) (-map 'square) (-reduce '+))
⇒ 14
-- Macro: --> (x &rest forms)
Starting with the value of X, thread each expression through FORMS.
Insert X at the position signified by the symbol ‘it’ in the first
form. If there are more forms, insert the first form at the
position signified by ‘it’ in the second form, etc.
(--> "def" (concat "abc" it "ghi"))
⇒ "abcdefghi"
(--> "def" (concat "abc" it "ghi") (upcase it))
⇒ "ABCDEFGHI"
(--> "def" (concat "abc" it "ghi") upcase)
⇒ "ABCDEFGHI"
-- Macro: -as-> (value variable &rest forms)
Starting with VALUE, thread VARIABLE through FORMS.
In the first form, bind VARIABLE to VALUE. In the second form,
bind VARIABLE to the result of the first form, and so forth.
(-as-> 3 my-var (1+ my-var) (list my-var) (mapcar (lambda (ele) (* 2 ele)) my-var))
⇒ (8)
(-as-> 3 my-var 1+)
⇒ 4
(-as-> 3 my-var)
⇒ 3
-- Macro: -some-> (x &optional form &rest more)
When expr is non-‘nil’, thread it through the first form (via ‘->’
(*note ->::)), and when that result is non-‘nil’, through the next
form, etc.
(-some-> '(2 3 5))
⇒ (2 3 5)
(-some-> 5 square)
⇒ 25
(-some-> 5 even? square)
⇒ nil
-- Macro: -some->> (x &optional form &rest more)
When expr is non-‘nil’, thread it through the first form (via ‘->>’
(*note ->>::)), and when that result is non-‘nil’, through the next
form, etc.
(-some->> '(1 2 3) (-map 'square))
⇒ (1 4 9)
(-some->> '(1 3 5) (-last 'even?) (+ 100))
⇒ nil
(-some->> '(2 4 6) (-last 'even?) (+ 100))
⇒ 106
-- Macro: -some--> (expr &rest forms)
Thread EXPR through FORMS via ‘-->’ (*note -->::), while the result
is non-‘nil’. When EXPR evaluates to non-‘nil’, thread the result
through the first of FORMS, and when that result is non-‘nil’,
thread it through the next form, etc.
(-some--> "def" (concat "abc" it "ghi"))
⇒ "abcdefghi"
(-some--> nil (concat "abc" it "ghi"))
⇒ nil
(-some--> '(0 1) (-remove #'natnump it) (append it it) (-map #'1+ it))
⇒ ()
-- Macro: -doto (init &rest forms)
Evaluate INIT and pass it as argument to FORMS with ‘->’ (*note
->::). The RESULT of evaluating INIT is threaded through each of
FORMS individually using ‘->’ (*note ->::), which see. The return
value is RESULT, which FORMS may have modified by side effect.
(-doto (list 1 2 3) pop pop)
⇒ (3)
(-doto (cons 1 2) (setcar 3) (setcdr 4))
⇒ (3 . 4)
(gethash 'k (--doto (make-hash-table) (puthash 'k 'v it)))
⇒ v

File: dash.info, Node: Binding, Next: Side effects, Prev: Threading macros, Up: Functions
2.13 Binding
============
Macros that combine ‘let’ and ‘let*’ with destructuring and flow
control.
-- Macro: -when-let ((var val) &rest body)
If VAL evaluates to non-‘nil’, bind it to VAR and execute body.
Note: binding is done according to ‘-let’ (*note -let::).
(-when-let (match-index (string-match "d" "abcd")) (+ match-index 2))
⇒ 5
(-when-let ((&plist :foo foo) (list :foo "foo")) foo)
⇒ "foo"
(-when-let ((&plist :foo foo) (list :bar "bar")) foo)
⇒ nil
-- Macro: -when-let* (vars-vals &rest body)
If all VALS evaluate to true, bind them to their corresponding VARS
and execute body. VARS-VALS should be a list of (VAR VAL) pairs.
Note: binding is done according to ‘-let*’ (*note -let*::). VALS
are evaluated sequentially, and evaluation stops after the first
‘nil’ VAL is encountered.
(-when-let* ((x 5) (y 3) (z (+ y 4))) (+ x y z))
⇒ 15
(-when-let* ((x 5) (y nil) (z 7)) (+ x y z))
⇒ nil
-- Macro: -if-let ((var val) then &rest else)
If VAL evaluates to non-‘nil’, bind it to VAR and do THEN,
otherwise do ELSE.
Note: binding is done according to ‘-let’ (*note -let::).
(-if-let (match-index (string-match "d" "abc")) (+ match-index 3) 7)
⇒ 7
(--if-let (even? 4) it nil)
⇒ t
-- Macro: -if-let* (vars-vals then &rest else)
If all VALS evaluate to true, bind them to their corresponding VARS
and do THEN, otherwise do ELSE. VARS-VALS should be a list of (VAR
VAL) pairs.
Note: binding is done according to ‘-let*’ (*note -let*::). VALS
are evaluated sequentially, and evaluation stops after the first
‘nil’ VAL is encountered.
(-if-let* ((x 5) (y 3) (z 7)) (+ x y z) "foo")
⇒ 15
(-if-let* ((x 5) (y nil) (z 7)) (+ x y z) "foo")
⇒ "foo"
(-if-let* (((_ _ x) '(nil nil 7))) x)
⇒ 7
-- Macro: -let (varlist &rest body)
Bind variables according to VARLIST then eval BODY.
VARLIST is a list of lists of the form (PATTERN SOURCE). Each
PATTERN is matched against the SOURCE "structurally". SOURCE is
only evaluated once for each PATTERN. Each PATTERN is matched
recursively, and can therefore contain sub-patterns which are
matched against corresponding sub-expressions of SOURCE.
All the SOURCEs are evalled before any symbols are bound (i.e. "in
parallel").
If VARLIST only contains one (PATTERN SOURCE) element, you can
optionally specify it using a vector and discarding the outer-most
parens. Thus
(-let ((PATTERN SOURCE)) ...)
becomes
(-let [PATTERN SOURCE] ...).
‘-let’ (*note -let::) uses a convention of not binding places
(symbols) starting with _ whenever it’s possible. You can use this
to skip over entries you don’t care about. However, this is not
*always* possible (as a result of implementation) and these symbols
might get bound to undefined values.
Following is the overview of supported patterns. Remember that
patterns can be matched recursively, so every a, b, aK in the
following can be a matching construct and not necessarily a
symbol/variable.
Symbol:
a - bind the SOURCE to A. This is just like regular ‘let’.
Conses and lists:
(a) - bind ‘car’ of cons/list to A
(a . b) - bind car of cons to A and ‘cdr’ to B
(a b) - bind car of list to A and ‘cadr’ to B
(a1 a2 a3 ...) - bind 0th car of list to A1, 1st to A2, 2nd to
A3...
(a1 a2 a3 ... aN . rest) - as above, but bind the Nth cdr to REST.
Vectors:
[a] - bind 0th element of a non-list sequence to A (works with
vectors, strings, bit arrays...)
[a1 a2 a3 ...] - bind 0th element of non-list sequence to A0, 1st
to A1, 2nd to A2, ... If the PATTERN is shorter than SOURCE, the
values at places not in PATTERN are ignored. If the PATTERN is
longer than SOURCE, an ‘error’ is thrown.
[a1 a2 a3 ... &rest rest] - as above, but bind the rest of the
sequence to REST. This is conceptually the same as improper list
matching (a1 a2 ... aN . rest)
Key/value stores:
(&plist key0 a0 ... keyN aN) - bind value mapped by keyK in the
SOURCE plist to aK. If the value is not found, aK is ‘nil’. Uses
‘plist-get’ to fetch values.
(&alist key0 a0 ... keyN aN) - bind value mapped by keyK in the
SOURCE alist to aK. If the value is not found, aK is ‘nil’. Uses
‘assoc’ to fetch values.
(&hash key0 a0 ... keyN aN) - bind value mapped by keyK in the
SOURCE hash table to aK. If the value is not found, aK is ‘nil’.
Uses ‘gethash’ to fetch values.
Further, special keyword &keys supports "inline" matching of
plist-like key-value pairs, similarly to &keys keyword of
‘cl-defun’.
(a1 a2 ... aN &keys key1 b1 ... keyN bK)
This binds N values from the list to a1 ... aN, then interprets the
cdr as a plist (see key/value matching above).
A shorthand notation for kv-destructuring exists which allows the
patterns be optionally left out and derived from the key name in
the following fashion:
- a key :foo is converted into ‘foo’ pattern, - a key ’bar is
converted into ‘bar’ pattern, - a key "baz" is converted into ‘baz’
pattern.
That is, the entire value under the key is bound to the derived
variable without any further destructuring.
This is possible only when the form following the key is not a
valid pattern (i.e. not a symbol, a cons cell or a vector).
Otherwise the matching proceeds as usual and in case of an invalid
spec fails with an error.
Thus the patterns are normalized as follows:
;; derive all the missing patterns (&plist :foo ’bar "baz") =>
(&plist :foo foo ’bar bar "baz" baz)
;; we can specify some but not others (&plist :foo ’bar
explicit-bar) => (&plist :foo foo ’bar explicit-bar)
;; nothing happens, we store :foo in x (&plist :foo x) => (&plist
:foo x)
;; nothing happens, we match recursively (&plist :foo (a b c)) =>
(&plist :foo (a b c))
You can name the source using the syntax SYMBOL &as PATTERN. This
syntax works with lists (proper or improper), vectors and all types
of maps.
(list &as a b c) (list 1 2 3)
binds A to 1, B to 2, C to 3 and LIST to (1 2 3).
Similarly:
(bounds &as beg . end) (cons 1 2)
binds BEG to 1, END to 2 and BOUNDS to (1 . 2).
(items &as first . rest) (list 1 2 3)
binds FIRST to 1, REST to (2 3) and ITEMS to (1 2 3)
[vect &as _ b c] [1 2 3]
binds B to 2, C to 3 and VECT to [1 2 3] (_ avoids binding as
usual).
(plist &as &plist :b b) (list :a 1 :b 2 :c 3)
binds B to 2 and PLIST to (:a 1 :b 2 :c 3). Same for &alist and
&hash.
This is especially useful when we want to capture the result of a
computation and destructure at the same time. Consider the form
(function-returning-complex-structure) returning a list of two
vectors with two items each. We want to capture this entire result
and pass it to another computation, but at the same time we want to
get the second item from each vector. We can achieve it with
pattern
(result &as [_ a] [_ b]) (function-returning-complex-structure)
Note: Clojure programmers may know this feature as the ":as
binding". The difference is that we put the &as at the front
because we need to support improper list binding.
(-let (([a (b c) d] [1 (2 3) 4])) (list a b c d))
⇒ (1 2 3 4)
(-let [(a b c . d) (list 1 2 3 4 5 6)] (list a b c d))
⇒ (1 2 3 (4 5 6))
(-let [(&plist :foo foo :bar bar) (list :baz 3 :foo 1 :qux 4 :bar 2)] (list foo bar))
⇒ (1 2)
-- Macro: -let* (varlist &rest body)
Bind variables according to VARLIST then eval BODY.
VARLIST is a list of lists of the form (PATTERN SOURCE). Each
PATTERN is matched against the SOURCE structurally. SOURCE is only
evaluated once for each PATTERN.
Each SOURCE can refer to the symbols already bound by this VARLIST.
This is useful if you want to destructure SOURCE recursively but
also want to name the intermediate structures.
See ‘-let’ (*note -let::) for the list of all possible patterns.
(-let* (((a . b) (cons 1 2)) ((c . d) (cons 3 4))) (list a b c d))
⇒ (1 2 3 4)
(-let* (((a . b) (cons 1 (cons 2 3))) ((c . d) b)) (list a b c d))
⇒ (1 (2 . 3) 2 3)
(-let* (((&alist "foo" foo "bar" bar) (list (cons "foo" 1) (cons "bar" (list 'a 'b 'c)))) ((a b c) bar)) (list foo a b c bar))
⇒ (1 a b c (a b c))
-- Macro: -lambda (match-form &rest body)
Return a lambda which destructures its input as MATCH-FORM and
executes BODY.
Note that you have to enclose the MATCH-FORM in a pair of parens,
such that:
(-lambda (x) body) (-lambda (x y ...) body)
has the usual semantics of ‘lambda’. Furthermore, these get
translated into normal ‘lambda’, so there is no performance
penalty.
See ‘-let’ (*note -let::) for a description of the destructuring
mechanism.
(-map (-lambda ((x y)) (+ x y)) '((1 2) (3 4) (5 6)))
⇒ (3 7 11)
(-map (-lambda ([x y]) (+ x y)) '([1 2] [3 4] [5 6]))
⇒ (3 7 11)
(funcall (-lambda ((_ . a) (_ . b)) (-concat a b)) '(1 2 3) '(4 5 6))
⇒ (2 3 5 6)
-- Macro: -setq ([match-form val] ...)
Bind each MATCH-FORM to the value of its VAL.
MATCH-FORM destructuring is done according to the rules of ‘-let’
(*note -let::).
This macro allows you to bind multiple variables by destructuring
the value, so for example:
(-setq (a b) x (&plist :c c) plist)
expands roughly speaking to the following code
(setq a (car x) b (cadr x) c (plist-get plist :c))
Care is taken to only evaluate each VAL once so that in case of
multiple assignments it does not cause unexpected side effects.
(let (a) (-setq a 1) a)
⇒ 1
(let (a b) (-setq (a b) (list 1 2)) (list a b))
⇒ (1 2)
(let (c) (-setq (&plist :c c) (list :c "c")) c)
⇒ "c"

File: dash.info, Node: Side effects, Next: Destructive operations, Prev: Binding, Up: Functions
2.14 Side effects
=================
Functions iterating over lists for side effect only.
-- Function: -each (list fn)
Call FN on each element of LIST. Return ‘nil’; this function is
intended for side effects.
Its anaphoric counterpart is ‘--each’.
For access to the current element’s index in LIST, see
‘-each-indexed’ (*note -each-indexed::).
(let (l) (-each '(1 2 3) (lambda (x) (push x l))) l)
⇒ (3 2 1)
(let (l) (--each '(1 2 3) (push it l)) l)
⇒ (3 2 1)
(-each '(1 2 3) #'identity)
⇒ nil
-- Function: -each-while (list pred fn)
Call FN on each ITEM in LIST, while (PRED ITEM) is non-‘nil’. Once
an ITEM is reached for which PRED returns ‘nil’, FN is no longer
called. Return ‘nil’; this function is intended for side effects.
Its anaphoric counterpart is ‘--each-while’.
(let (l) (-each-while '(2 4 5 6) #'even? (lambda (x) (push x l))) l)
⇒ (4 2)
(let (l) (--each-while '(1 2 3 4) (< it 3) (push it l)) l)
⇒ (2 1)
(let ((s 0)) (--each-while '(1 3 4 5) (< it 5) (setq s (+ s it))) s)
⇒ 8
-- Function: -each-indexed (list fn)
Call FN on each index and element of LIST. For each ITEM at INDEX
in LIST, call (funcall FN INDEX ITEM). Return ‘nil’; this function
is intended for side effects.
See also: ‘-map-indexed’ (*note -map-indexed::).
(let (l) (-each-indexed '(a b c) (lambda (i x) (push (list x i) l))) l)
⇒ ((c 2) (b 1) (a 0))
(let (l) (--each-indexed '(a b c) (push (list it it-index) l)) l)
⇒ ((c 2) (b 1) (a 0))
(let (l) (--each-indexed () (push it l)) l)
⇒ ()
-- Function: -each-r (list fn)
Call FN on each element of LIST in reversed order. Return ‘nil’;
this function is intended for side effects.
Its anaphoric counterpart is ‘--each-r’.
(let (l) (-each-r '(1 2 3) (lambda (x) (push x l))) l)
⇒ (1 2 3)
(let (l) (--each-r '(1 2 3) (push it l)) l)
⇒ (1 2 3)
(-each-r '(1 2 3) #'identity)
⇒ nil
-- Function: -each-r-while (list pred fn)
Call FN on each ITEM in reversed LIST, while (PRED ITEM) is
non-‘nil’. Once an ITEM is reached for which PRED returns ‘nil’,
FN is no longer called. Return ‘nil’; this function is intended
for side effects.
Its anaphoric counterpart is ‘--each-r-while’.
(let (l) (-each-r-while '(2 4 5 6) #'even? (lambda (x) (push x l))) l)
⇒ (6)
(let (l) (--each-r-while '(1 2 3 4) (>= it 3) (push it l)) l)
⇒ (3 4)
(let ((s 0)) (--each-r-while '(1 2 3 5) (> it 1) (setq s (+ s it))) s)
⇒ 10
-- Function: -dotimes (num fn)
Call FN NUM times, presumably for side effects. FN is called with
a single argument on successive integers running from 0, inclusive,
to NUM, exclusive. FN is not called if NUM is less than 1.
This function’s anaphoric counterpart is ‘--dotimes’.
(let (s) (-dotimes 3 (lambda (n) (push n s))) s)
⇒ (2 1 0)
(let (s) (-dotimes 0 (lambda (n) (push n s))) s)
⇒ ()
(let (s) (--dotimes 5 (push it s)) s)
⇒ (4 3 2 1 0)

File: dash.info, Node: Destructive operations, Next: Function combinators, Prev: Side effects, Up: Functions
2.15 Destructive operations
===========================
Macros that modify variables holding lists.
-- Macro: !cons (car cdr)
Destructive: Set CDR to the cons of CAR and CDR.
(let (l) (!cons 5 l) l)
⇒ (5)
(let ((l '(3))) (!cons 5 l) l)
⇒ (5 3)
-- Macro: !cdr (list)
Destructive: Set LIST to the cdr of LIST.
(let ((l '(3))) (!cdr l) l)
⇒ ()
(let ((l '(3 5))) (!cdr l) l)
⇒ (5)

File: dash.info, Node: Function combinators, Prev: Destructive operations, Up: Functions
2.16 Function combinators
=========================
Functions that manipulate and compose other functions.
-- Function: -partial (fun &rest args)
Return a function that is a partial application of FUN to ARGS.
ARGS is a list of the first N arguments to pass to FUN. The result
is a new function which does the same as FUN, except that the first
N arguments are fixed at the values with which this function was
called.
(funcall (-partial #'+ 5))
⇒ 5
(funcall (-partial #'- 5) 3)
⇒ 2
(funcall (-partial #'+ 5 2) 3)
⇒ 10
-- Function: -rpartial (fn &rest args)
Return a function that is a partial application of FN to ARGS.
ARGS is a list of the last N arguments to pass to FN. The result
is a new function which does the same as FN, except that the last N
arguments are fixed at the values with which this function was
called. This is like ‘-partial’ (*note -partial::), except the
arguments are fixed starting from the right rather than the left.
(funcall (-rpartial #'- 5))
⇒ -5
(funcall (-rpartial #'- 5) 8)
⇒ 3
(funcall (-rpartial #'- 5 2) 10)
⇒ 3
-- Function: -juxt (&rest fns)
Return a function that is the juxtaposition of FNS. The returned
function takes a variable number of ARGS, applies each of FNS in
turn to ARGS, and returns the list of results.
(funcall (-juxt) 1 2)
⇒ ()
(funcall (-juxt #'+ #'- #'* #'/) 7 5)
⇒ (12 2 35 1)
(mapcar (-juxt #'number-to-string #'1+) '(1 2))
⇒ (("1" 2) ("2" 3))
-- Function: -compose (&rest fns)
Compose FNS into a single composite function. Return a function
that takes a variable number of ARGS, applies the last function in
FNS to ARGS, and returns the result of calling each remaining
function on the result of the previous function, right-to-left. If
no FNS are given, return a variadic ‘identity’ function.
(funcall (-compose #'- #'1+ #'+) 1 2 3)
⇒ -7
(funcall (-compose #'identity #'1+) 3)
⇒ 4
(mapcar (-compose #'not #'stringp) '(nil ""))
⇒ (t nil)
-- Function: -applify (fn)
Return a function that applies FN to a single list of args. This
changes the arity of FN from taking N distinct arguments to taking
1 argument which is a list of N arguments.
(funcall (-applify #'+) nil)
⇒ 0
(mapcar (-applify #'+) '((1 1 1) (1 2 3) (5 5 5)))
⇒ (3 6 15)
(funcall (-applify #'<) '(3 6))
⇒ t
-- Function: -on (op trans)
Return a function that calls TRANS on each arg and OP on the
results. The returned function takes a variable number of
arguments, calls the function TRANS on each one in turn, and then
passes those results as the list of arguments to OP, in the same
order.
For example, the following pairs of expressions are morally
equivalent:
(funcall (-on #’+ #’1+) 1 2 3) = (+ (1+ 1) (1+ 2) (1+ 3)) (funcall
(-on #’+ #’1+)) = (+)
(-sort (-on #'< #'length) '((1 2 3) (1) (1 2)))
⇒ ((1) (1 2) (1 2 3))
(funcall (-on #'min #'string-to-number) "22" "2" "1" "12")
⇒ 1
(-min-by (-on #'> #'length) '((1 2 3) (4) (1 2)))
⇒ (4)
-- Function: -flip (fn)
Return a function that calls FN with its arguments reversed. The
returned function takes the same number of arguments as FN.
For example, the following two expressions are morally equivalent:
(funcall (-flip #’-) 1 2) = (- 2 1)
See also: ‘-rotate-args’ (*note -rotate-args::).
(-sort (-flip #'<) '(4 3 6 1))
⇒ (6 4 3 1)
(funcall (-flip #'-) 3 2 1 10)
⇒ 4
(funcall (-flip #'1+) 1)
⇒ 2
-- Function: -rotate-args (n fn)
Return a function that calls FN with args rotated N places to the
right. The returned function takes the same number of arguments as
FN, rotates the list of arguments N places to the right (left if N
is negative) just like ‘-rotate’ (*note -rotate::), and applies FN
to the result.
See also: ‘-flip’ (*note -flip::).
(funcall (-rotate-args -1 #'list) 1 2 3 4)
⇒ (2 3 4 1)
(funcall (-rotate-args 1 #'-) 1 10 100)
⇒ 89
(funcall (-rotate-args 2 #'list) 3 4 5 1 2)
⇒ (1 2 3 4 5)
-- Function: -const (c)
Return a function that returns C ignoring any additional arguments.
In types: a -> b -> a
(funcall (-const 2) 1 3 "foo")
⇒ 2
(mapcar (-const 1) '("a" "b" "c" "d"))
⇒ (1 1 1 1)
(-sum (mapcar (-const 1) '("a" "b" "c" "d")))
⇒ 4
-- Macro: -cut (&rest params)
Take n-ary function and n arguments and specialize some of them.
Arguments denoted by <> will be left unspecialized.
See SRFI-26 for detailed description.
(funcall (-cut list 1 <> 3 <> 5) 2 4)
⇒ (1 2 3 4 5)
(-map (-cut funcall <> 5) `(1+ 1- ,(lambda (x) (/ 1.0 x))))
⇒ (6 4 0.2)
(-map (-cut <> 1 2 3) '(list vector string))
⇒ ((1 2 3) [1 2 3] "\1\2\3")
-- Function: -not (pred)
Return a predicate that negates the result of PRED. The returned
predicate passes its arguments to PRED. If PRED returns ‘nil’, the
result is non-‘nil’; otherwise the result is ‘nil’.
See also: ‘-andfn’ (*note -andfn::) and ‘-orfn’ (*note -orfn::).
(funcall (-not #'numberp) "5")
⇒ t
(-sort (-not #'<) '(5 2 1 0 6))
⇒ (6 5 2 1 0)
(-filter (-not (-partial #'< 4)) '(1 2 3 4 5 6 7 8))
⇒ (1 2 3 4)
-- Function: -orfn (&rest preds)
Return a predicate that returns the first non-‘nil’ result of
PREDS. The returned predicate takes a variable number of
arguments, passes them to each predicate in PREDS in turn until one
of them returns non-‘nil’, and returns that non-‘nil’ result
without calling the remaining PREDS. If all PREDS return ‘nil’, or
if no PREDS are given, the returned predicate returns ‘nil’.
See also: ‘-andfn’ (*note -andfn::) and ‘-not’ (*note -not::).
(-filter (-orfn #'natnump #'booleanp) '(1 nil "a" -4 b c t))
⇒ (1 nil t)
(funcall (-orfn #'symbolp (-cut string-match-p "x" <>)) "axe")
⇒ 1
(funcall (-orfn #'= #'+) 1 1)
⇒ t
-- Function: -andfn (&rest preds)
Return a predicate that returns non-‘nil’ if all PREDS do so. The
returned predicate P takes a variable number of arguments and
passes them to each predicate in PREDS in turn. If any one of
PREDS returns ‘nil’, P also returns ‘nil’ without calling the
remaining PREDS. If all PREDS return non-‘nil’, P returns the last
such value. If no PREDS are given, P always returns non-‘nil’.
See also: ‘-orfn’ (*note -orfn::) and ‘-not’ (*note -not::).
(-filter (-andfn #'numberp (-cut < <> 5)) '(a 1 b 6 c 2))
⇒ (1 2)
(mapcar (-andfn #'numberp #'1+) '(a 1 b 6))
⇒ (nil 2 nil 7)
(funcall (-andfn #'= #'+) 1 1)
⇒ 2
-- Function: -iteratefn (fn n)
Return a function FN composed N times with itself.
FN is a unary function. If you need to use a function of higher
arity, use ‘-applify’ (*note -applify::) first to turn it into a
unary function.
With n = 0, this acts as identity function.
In types: (a -> a) -> Int -> a -> a.
This function satisfies the following law:
(funcall (-iteratefn fn n) init) = (-last-item (-iterate fn init
(1+ n))).
(funcall (-iteratefn (lambda (x) (* x x)) 3) 2)
⇒ 256
(funcall (-iteratefn '1+ 3) 1)
⇒ 4
(funcall (-iteratefn 'cdr 3) '(1 2 3 4 5))
⇒ (4 5)
-- Function: -fixfn (fn &optional equal-test halt-test)
Return a function that computes the (least) fixpoint of FN.
FN must be a unary function. The returned lambda takes a single
argument, X, the initial value for the fixpoint iteration. The
iteration halts when either of the following conditions is
satisfied:
1. Iteration converges to the fixpoint, with equality being tested
using EQUAL-TEST. If EQUAL-TEST is not specified, ‘equal’ is used.
For functions over the floating point numbers, it may be necessary
to provide an appropriate approximate comparison test.
2. HALT-TEST returns a non-‘nil’ value. HALT-TEST defaults to a
simple counter that returns ‘t’ after ‘-fixfn-max-iterations’, to
guard against infinite iteration. Otherwise, HALT-TEST must be a
function that accepts a single argument, the current value of X,
and returns non-‘nil’ as long as iteration should continue. In
this way, a more sophisticated convergence test may be supplied by
the caller.
The return value of the lambda is either the fixpoint or, if
iteration halted before converging, a cons with car ‘halted’ and
cdr the final output from HALT-TEST.
In types: (a -> a) -> a -> a.
(funcall (-fixfn #'cos #'approx=) 0.7)
⇒ 0.7390851332151607
(funcall (-fixfn (lambda (x) (expt (+ x 10) 0.25))) 2.0)
⇒ 1.8555845286409378
(funcall (-fixfn #'sin #'approx=) 0.1)
⇒ (halted . t)
-- Function: -prodfn (&rest fns)
Return a function that applies each of FNS to each of a list of
arguments.
Takes a list of N functions and returns a function that takes a
list of length N, applying Ith function to Ith element of the input
list. Returns a list of length N.
In types (for N=2): ((a -> b), (c -> d)) -> (a, c) -> (b, d)
This function satisfies the following laws:
(-compose (-prodfn f g ...) (-prodfn f’ g’ ...)) = (-prodfn
(-compose f f’) (-compose g g’) ...)
(-prodfn f g ...) = (-juxt (-compose f (-partial #’nth 0))
(-compose g (-partial #’nth 1)) ...)
(-compose (-prodfn f g ...) (-juxt f’ g’ ...)) = (-juxt (-compose f
f’) (-compose g g’) ...)
(-compose (-partial #’nth n) (-prod f1 f2 ...)) = (-compose fn
(-partial #’nth n))
(funcall (-prodfn #'1+ #'1- #'number-to-string) '(1 2 3))
⇒ (2 1 "3")
(-map (-prodfn #'1- #'1+) '((1 2) (3 4) (5 6)))
⇒ ((0 3) (2 5) (4 7))
(apply #'+ (funcall (-prodfn #'length #'string-to-number) '((t) "5")))
⇒ 6

File: dash.info, Node: Development, Next: FDL, Prev: Functions, Up: Top
3 Development
*************
The Dash repository is hosted on GitHub at
<https://github.com/magnars/dash.el>.
* Menu:
* Contribute:: How to contribute.
* Contributors:: List of contributors.

File: dash.info, Node: Contribute, Next: Contributors, Up: Development
3.1 Contribute
==============
Yes, please do. Pure functions in the list manipulation realm only,
please. There’s a suite of examples/tests in ‘dev/examples.el’, so
remember to add tests for your additions, or they may get broken later.
Run the tests with ‘make check’. Regenerate the docs with ‘make
docs’. Contributors are encouraged to install these commands as a Git
pre-commit hook, so that the tests are always running and the docs are
always in sync:
$ cp dev/pre-commit.sh .git/hooks/pre-commit
Oh, and don’t edit ‘README.md’ or ‘dash.texi’ directly, as they are
auto-generated. Instead, change their respective templates
‘readme-template.md’ or ‘dash-template.texi’.
To ensure that Dash can be distributed with GNU ELPA or Emacs, we
require that all contributors assign copyright to the Free Software
Foundation. For more on this, *note (emacs)Copyright Assignment::.

File: dash.info, Node: Contributors, Prev: Contribute, Up: Development
3.2 Contributors
================
• Matus Goljer (https://github.com/Fuco1) contributed lots of
features and functions.
• Takafumi Arakaki (https://github.com/tkf) contributed ‘-group-by’.
• tali713 (https://github.com/tali713) is the author of ‘-applify’.
• Víctor M. Valenzuela (https://github.com/vemv) contributed
‘-repeat’.
• Nic Ferrier (https://github.com/nicferrier) contributed ‘-cons*’.
• Wilfred Hughes (https://github.com/Wilfred) contributed ‘-slice’,
‘-first-item’, and ‘-last-item’.
• Emanuel Evans (https://github.com/shosti) contributed ‘-if-let’,
‘-when-let’, and ‘-insert-at’.
• Johan Andersson (https://github.com/rejeep) contributed ‘-sum’,
‘-product’, and ‘-same-items?’.
• Christina Whyte (https://github.com/kurisuwhyte) contributed
‘-compose’.
• Steve Lamb (https://github.com/steventlamb) contributed ‘-cycle’,
‘-pad’, ‘-annotate’, ‘-zip-fill’, and a variadic version of ‘-zip’.
• Fredrik Bergroth (https://github.com/fbergroth) made the ‘-if-let’
family use ‘-let’ destructuring and improved the script for
generating documentation.
• Mark Oteiza (https://github.com/holomorph) contributed ‘-iota’ and
the script to create an Info manual.
• Vasilij Schneidermann (https://github.com/wasamasa) contributed
‘-some’.
• William West (https://github.com/occidens) made ‘-fixfn’ more
robust at handling floats.
• Cam Saul (https://github.com/camsaul) contributed ‘-some->’,
‘-some->>’, and ‘-some-->’.
• Basil L. Contovounesios (https://github.com/basil-conto)
contributed ‘-common-prefix’, ‘-common-suffix’, and various other
improvements.
• Paul Pogonyshev (https://github.com/doublep) contributed ‘-each-r’
and ‘-each-r-while’.
Thanks!
New contributors are very welcome. *Note Contribute::.

File: dash.info, Node: FDL, Next: GPL, Prev: Development, Up: Top
Appendix A GNU Free Documentation License
*****************************************
Version 1.3, 3 November 2008
Copyright © 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
<https://fsf.org/>
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
0. PREAMBLE
The purpose of this License is to make a manual, textbook, or other
functional and useful document “free” in the sense of freedom: to
assure everyone the effective freedom to copy and redistribute it,
with or without modifying it, either commercially or
noncommercially. Secondarily, this License preserves for the
author and publisher a way to get credit for their work, while not
being considered responsible for modifications made by others.
This License is a kind of “copyleft”, which means that derivative
works of the document must themselves be free in the same sense.
It complements the GNU General Public License, which is a copyleft
license designed for free software.
We have designed this License in order to use it for manuals for
free software, because free software needs free documentation: a
free program should come with manuals providing the same freedoms
that the software does. But this License is not limited to
software manuals; it can be used for any textual work, regardless
of subject matter or whether it is published as a printed book. We
recommend this License principally for works whose purpose is
instruction or reference.
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A “Modified Version” of the Document means any work containing the
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You may add a passage of up to five words as a Front-Cover Text,
and a passage of up to 25 words as a Back-Cover Text, to the end of
the list of Cover Texts in the Modified Version. Only one passage
of Front-Cover Text and one of Back-Cover Text may be added by (or
through arrangements made by) any one entity. If the Document
already includes a cover text for the same cover, previously added
by you or by arrangement made by the same entity you are acting on
behalf of, you may not add another; but you may replace the old
one, on explicit permission from the previous publisher that added
the old one.
The author(s) and publisher(s) of the Document do not by this
License give permission to use their names for publicity for or to
assert or imply endorsement of any Modified Version.
5. COMBINING DOCUMENTS
You may combine the Document with other documents released under
this License, under the terms defined in section 4 above for
modified versions, provided that you include in the combination all
of the Invariant Sections of all of the original documents,
unmodified, and list them all as Invariant Sections of your
combined work in its license notice, and that you preserve all
their Warranty Disclaimers.
The combined work need only contain one copy of this License, and
multiple identical Invariant Sections may be replaced with a single
copy. If there are multiple Invariant Sections with the same name
but different contents, make the title of each such section unique
by adding at the end of it, in parentheses, the name of the
original author or publisher of that section if known, or else a
unique number. Make the same adjustment to the section titles in
the list of Invariant Sections in the license notice of the
combined work.
In the combination, you must combine any sections Entitled
“History” in the various original documents, forming one section
Entitled “History”; likewise combine any sections Entitled
“Acknowledgements”, and any sections Entitled “Dedications”. You
must delete all sections Entitled “Endorsements.”
6. COLLECTIONS OF DOCUMENTS
You may make a collection consisting of the Document and other
documents released under this License, and replace the individual
copies of this License in the various documents with a single copy
that is included in the collection, provided that you follow the
rules of this License for verbatim copying of each of the documents
in all other respects.
You may extract a single document from such a collection, and
distribute it individually under this License, provided you insert
a copy of this License into the extracted document, and follow this
License in all other respects regarding verbatim copying of that
document.
7. AGGREGATION WITH INDEPENDENT WORKS
A compilation of the Document or its derivatives with other
separate and independent documents or works, in or on a volume of a
storage or distribution medium, is called an “aggregate” if the
copyright resulting from the compilation is not used to limit the
legal rights of the compilation’s users beyond what the individual
works permit. When the Document is included in an aggregate, this
License does not apply to the other works in the aggregate which
are not themselves derivative works of the Document.
If the Cover Text requirement of section 3 is applicable to these
copies of the Document, then if the Document is less than one half
of the entire aggregate, the Document’s Cover Texts may be placed
on covers that bracket the Document within the aggregate, or the
electronic equivalent of covers if the Document is in electronic
form. Otherwise they must appear on printed covers that bracket
the whole aggregate.
8. TRANSLATION
Translation is considered a kind of modification, so you may
distribute translations of the Document under the terms of section
4. Replacing Invariant Sections with translations requires special
permission from their copyright holders, but you may include
translations of some or all Invariant Sections in addition to the
original versions of these Invariant Sections. You may include a
translation of this License, and all the license notices in the
Document, and any Warranty Disclaimers, provided that you also
include the original English version of this License and the
original versions of those notices and disclaimers. In case of a
disagreement between the translation and the original version of
this License or a notice or disclaimer, the original version will
prevail.
If a section in the Document is Entitled “Acknowledgements”,
“Dedications”, or “History”, the requirement (section 4) to
Preserve its Title (section 1) will typically require changing the
actual title.
9. TERMINATION
You may not copy, modify, sublicense, or distribute the Document
except as expressly provided under this License. Any attempt
otherwise to copy, modify, sublicense, or distribute it is void,
and will automatically terminate your rights under this License.
However, if you cease all violation of this License, then your
license from a particular copyright holder is reinstated (a)
provisionally, unless and until the copyright holder explicitly and
finally terminates your license, and (b) permanently, if the
copyright holder fails to notify you of the violation by some
reasonable means prior to 60 days after the cessation.
Moreover, your license from a particular copyright holder is
reinstated permanently if the copyright holder notifies you of the
violation by some reasonable means, this is the first time you have
received notice of violation of this License (for any work) from
that copyright holder, and you cure the violation prior to 30 days
after your receipt of the notice.
Termination of your rights under this section does not terminate
the licenses of parties who have received copies or rights from you
under this License. If your rights have been terminated and not
permanently reinstated, receipt of a copy of some or all of the
same material does not give you any rights to use it.
10. FUTURE REVISIONS OF THIS LICENSE
The Free Software Foundation may publish new, revised versions of
the GNU Free Documentation License from time to time. Such new
versions will be similar in spirit to the present version, but may
differ in detail to address new problems or concerns. See
<https://www.gnu.org/licenses/>.
Each version of the License is given a distinguishing version
number. If the Document specifies that a particular numbered
version of this License “or any later version” applies to it, you
have the option of following the terms and conditions either of
that specified version or of any later version that has been
published (not as a draft) by the Free Software Foundation. If the
Document does not specify a version number of this License, you may
choose any version ever published (not as a draft) by the Free
Software Foundation. If the Document specifies that a proxy can
decide which future versions of this License can be used, that
proxy’s public statement of acceptance of a version permanently
authorizes you to choose that version for the Document.
11. RELICENSING
“Massive Multiauthor Collaboration Site” (or “MMC Site”) means any
World Wide Web server that publishes copyrightable works and also
provides prominent facilities for anybody to edit those works. A
public wiki that anybody can edit is an example of such a server.
A “Massive Multiauthor Collaboration” (or “MMC”) contained in the
site means any set of copyrightable works thus published on the MMC
site.
“CC-BY-SA” means the Creative Commons Attribution-Share Alike 3.0
license published by Creative Commons Corporation, a not-for-profit
corporation with a principal place of business in San Francisco,
California, as well as future copyleft versions of that license
published by that same organization.
“Incorporate” means to publish or republish a Document, in whole or
in part, as part of another Document.
An MMC is “eligible for relicensing” if it is licensed under this
License, and if all works that were first published under this
License somewhere other than this MMC, and subsequently
incorporated in whole or in part into the MMC, (1) had no cover
texts or invariant sections, and (2) were thus incorporated prior
to November 1, 2008.
The operator of an MMC Site may republish an MMC contained in the
site under CC-BY-SA on the same site at any time before August 1,
2009, provided the MMC is eligible for relicensing.
ADDENDUM: How to use this License for your documents
====================================================
To use this License in a document you have written, include a copy of
the License in the document and put the following copyright and license
notices just after the title page:
Copyright (C) YEAR YOUR NAME.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3
or any later version published by the Free Software Foundation;
with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
Texts. A copy of the license is included in the section entitled ``GNU
Free Documentation License''.
If you have Invariant Sections, Front-Cover Texts and Back-Cover
Texts, replace the “with...Texts.” line with this:
with the Invariant Sections being LIST THEIR TITLES, with
the Front-Cover Texts being LIST, and with the Back-Cover Texts
being LIST.
If you have Invariant Sections without Cover Texts, or some other
combination of the three, merge those two alternatives to suit the
situation.
If your document contains nontrivial examples of program code, we
recommend releasing these examples in parallel under your choice of free
software license, such as the GNU General Public License, to permit
their use in free software.

File: dash.info, Node: GPL, Next: Index, Prev: FDL, Up: Top
Appendix B GNU General Public License
*************************************
Version 3, 29 June 2007
Copyright © 2007 Free Software Foundation, Inc. <https://fsf.org/>
Everyone is permitted to copy and distribute verbatim copies of this
license document, but changing it is not allowed.
Preamble
========
The GNU General Public License is a free, copyleft license for software
and other kinds of works.
The licenses for most software and other practical works are designed
to take away your freedom to share and change the works. By contrast,
the GNU General Public License is intended to guarantee your freedom to
share and change all versions of a program—to make sure it remains free
software for all its users. We, the Free Software Foundation, use the
GNU General Public License for most of our software; it applies also to
any other work released this way by its authors. You can apply it to
your programs, too.
When we speak of free software, we are referring to freedom, not
price. Our General Public Licenses are designed to make sure that you
have the freedom to distribute copies of free software (and charge for
them if you wish), that you receive source code or can get it if you
want it, that you can change the software or use pieces of it in new
free programs, and that you know you can do these things.
To protect your rights, we need to prevent others from denying you
these rights or asking you to surrender the rights. Therefore, you have
certain responsibilities if you distribute copies of the software, or if
you modify it: responsibilities to respect the freedom of others.
For example, if you distribute copies of such a program, whether
gratis or for a fee, you must pass on to the recipients the same
freedoms that you received. You must make sure that they, too, receive
or can get the source code. And you must show them these terms so they
know their rights.
Developers that use the GNU GPL protect your rights with two steps:
(1) assert copyright on the software, and (2) offer you this License
giving you legal permission to copy, distribute and/or modify it.
For the developers’ and authors’ protection, the GPL clearly explains
that there is no warranty for this free software. For both users’ and
authors’ sake, the GPL requires that modified versions be marked as
changed, so that their problems will not be attributed erroneously to
authors of previous versions.
Some devices are designed to deny users access to install or run
modified versions of the software inside them, although the manufacturer
can do so. This is fundamentally incompatible with the aim of
protecting users’ freedom to change the software. The systematic
pattern of such abuse occurs in the area of products for individuals to
use, which is precisely where it is most unacceptable. Therefore, we
have designed this version of the GPL to prohibit the practice for those
products. If such problems arise substantially in other domains, we
stand ready to extend this provision to those domains in future versions
of the GPL, as needed to protect the freedom of users.
Finally, every program is threatened constantly by software patents.
States should not allow patents to restrict development and use of
software on general-purpose computers, but in those that do, we wish to
avoid the special danger that patents applied to a free program could
make it effectively proprietary. To prevent this, the GPL assures that
patents cannot be used to render the program non-free.
The precise terms and conditions for copying, distribution and
modification follow.
TERMS AND CONDITIONS
====================
0. Definitions.
“This License” refers to version 3 of the GNU General Public
License.
“Copyright” also means copyright-like laws that apply to other
kinds of works, such as semiconductor masks.
“The Program” refers to any copyrightable work licensed under this
License. Each licensee is addressed as “you”. “Licensees” and
“recipients” may be individuals or organizations.
To “modify” a work means to copy from or adapt all or part of the
work in a fashion requiring copyright permission, other than the
making of an exact copy. The resulting work is called a “modified
version” of the earlier work or a work “based on” the earlier work.
A “covered work” means either the unmodified Program or a work
based on the Program.
To “propagate” a work means to do anything with it that, without
permission, would make you directly or secondarily liable for
infringement under applicable copyright law, except executing it on
a computer or modifying a private copy. Propagation includes
copying, distribution (with or without modification), making
available to the public, and in some countries other activities as
well.
To “convey” a work means any kind of propagation that enables other
parties to make or receive copies. Mere interaction with a user
through a computer network, with no transfer of a copy, is not
conveying.
An interactive user interface displays “Appropriate Legal Notices”
to the extent that it includes a convenient and prominently visible
feature that (1) displays an appropriate copyright notice, and (2)
tells the user that there is no warranty for the work (except to
the extent that warranties are provided), that licensees may convey
the work under this License, and how to view a copy of this
License. If the interface presents a list of user commands or
options, such as a menu, a prominent item in the list meets this
criterion.
1. Source Code.
The “source code” for a work means the preferred form of the work
for making modifications to it. “Object code” means any non-source
form of a work.
A “Standard Interface” means an interface that either is an
official standard defined by a recognized standards body, or, in
the case of interfaces specified for a particular programming
language, one that is widely used among developers working in that
language.
The “System Libraries” of an executable work include anything,
other than the work as a whole, that (a) is included in the normal
form of packaging a Major Component, but which is not part of that
Major Component, and (b) serves only to enable use of the work with
that Major Component, or to implement a Standard Interface for
which an implementation is available to the public in source code
form. A “Major Component”, in this context, means a major
essential component (kernel, window system, and so on) of the
specific operating system (if any) on which the executable work
runs, or a compiler used to produce the work, or an object code
interpreter used to run it.
The “Corresponding Source” for a work in object code form means all
the source code needed to generate, install, and (for an executable
work) run the object code and to modify the work, including scripts
to control those activities. However, it does not include the
work’s System Libraries, or general-purpose tools or generally
available free programs which are used unmodified in performing
those activities but which are not part of the work. For example,
Corresponding Source includes interface definition files associated
with source files for the work, and the source code for shared
libraries and dynamically linked subprograms that the work is
specifically designed to require, such as by intimate data
communication or control flow between those subprograms and other
parts of the work.
The Corresponding Source need not include anything that users can
regenerate automatically from other parts of the Corresponding
Source.
The Corresponding Source for a work in source code form is that
same work.
2. Basic Permissions.
All rights granted under this License are granted for the term of
copyright on the Program, and are irrevocable provided the stated
conditions are met. This License explicitly affirms your unlimited
permission to run the unmodified Program. The output from running
a covered work is covered by this License only if the output, given
its content, constitutes a covered work. This License acknowledges
your rights of fair use or other equivalent, as provided by
copyright law.
You may make, run and propagate covered works that you do not
convey, without conditions so long as your license otherwise
remains in force. You may convey covered works to others for the
sole purpose of having them make modifications exclusively for you,
or provide you with facilities for running those works, provided
that you comply with the terms of this License in conveying all
material for which you do not control copyright. Those thus making
or running the covered works for you must do so exclusively on your
behalf, under your direction and control, on terms that prohibit
them from making any copies of your copyrighted material outside
their relationship with you.
Conveying under any other circumstances is permitted solely under
the conditions stated below. Sublicensing is not allowed; section
10 makes it unnecessary.
3. Protecting Users’ Legal Rights From Anti-Circumvention Law.
No covered work shall be deemed part of an effective technological
measure under any applicable law fulfilling obligations under
article 11 of the WIPO copyright treaty adopted on 20 December
1996, or similar laws prohibiting or restricting circumvention of
such measures.
When you convey a covered work, you waive any legal power to forbid
circumvention of technological measures to the extent such
circumvention is effected by exercising rights under this License
with respect to the covered work, and you disclaim any intention to
limit operation or modification of the work as a means of
enforcing, against the work’s users, your or third parties’ legal
rights to forbid circumvention of technological measures.
4. Conveying Verbatim Copies.
You may convey verbatim copies of the Program’s source code as you
receive it, in any medium, provided that you conspicuously and
appropriately publish on each copy an appropriate copyright notice;
keep intact all notices stating that this License and any
non-permissive terms added in accord with section 7 apply to the
code; keep intact all notices of the absence of any warranty; and
give all recipients a copy of this License along with the Program.
You may charge any price or no price for each copy that you convey,
and you may offer support or warranty protection for a fee.
5. Conveying Modified Source Versions.
You may convey a work based on the Program, or the modifications to
produce it from the Program, in the form of source code under the
terms of section 4, provided that you also meet all of these
conditions:
a. The work must carry prominent notices stating that you
modified it, and giving a relevant date.
b. The work must carry prominent notices stating that it is
released under this License and any conditions added under
section 7. This requirement modifies the requirement in
section 4 to “keep intact all notices”.
c. You must license the entire work, as a whole, under this
License to anyone who comes into possession of a copy. This
License will therefore apply, along with any applicable
section 7 additional terms, to the whole of the work, and all
its parts, regardless of how they are packaged. This License
gives no permission to license the work in any other way, but
it does not invalidate such permission if you have separately
received it.
d. If the work has interactive user interfaces, each must display
Appropriate Legal Notices; however, if the Program has
interactive interfaces that do not display Appropriate Legal
Notices, your work need not make them do so.
A compilation of a covered work with other separate and independent
works, which are not by their nature extensions of the covered
work, and which are not combined with it such as to form a larger
program, in or on a volume of a storage or distribution medium, is
called an “aggregate” if the compilation and its resulting
copyright are not used to limit the access or legal rights of the
compilation’s users beyond what the individual works permit.
Inclusion of a covered work in an aggregate does not cause this
License to apply to the other parts of the aggregate.
6. Conveying Non-Source Forms.
You may convey a covered work in object code form under the terms
of sections 4 and 5, provided that you also convey the
machine-readable Corresponding Source under the terms of this
License, in one of these ways:
a. Convey the object code in, or embodied in, a physical product
(including a physical distribution medium), accompanied by the
Corresponding Source fixed on a durable physical medium
customarily used for software interchange.
b. Convey the object code in, or embodied in, a physical product
(including a physical distribution medium), accompanied by a
written offer, valid for at least three years and valid for as
long as you offer spare parts or customer support for that
product model, to give anyone who possesses the object code
either (1) a copy of the Corresponding Source for all the
software in the product that is covered by this License, on a
durable physical medium customarily used for software
interchange, for a price no more than your reasonable cost of
physically performing this conveying of source, or (2) access
to copy the Corresponding Source from a network server at no
charge.
c. Convey individual copies of the object code with a copy of the
written offer to provide the Corresponding Source. This
alternative is allowed only occasionally and noncommercially,
and only if you received the object code with such an offer,
in accord with subsection 6b.
d. Convey the object code by offering access from a designated
place (gratis or for a charge), and offer equivalent access to
the Corresponding Source in the same way through the same
place at no further charge. You need not require recipients
to copy the Corresponding Source along with the object code.
If the place to copy the object code is a network server, the
Corresponding Source may be on a different server (operated by
you or a third party) that supports equivalent copying
facilities, provided you maintain clear directions next to the
object code saying where to find the Corresponding Source.
Regardless of what server hosts the Corresponding Source, you
remain obligated to ensure that it is available for as long as
needed to satisfy these requirements.
e. Convey the object code using peer-to-peer transmission,
provided you inform other peers where the object code and
Corresponding Source of the work are being offered to the
general public at no charge under subsection 6d.
A separable portion of the object code, whose source code is
excluded from the Corresponding Source as a System Library, need
not be included in conveying the object code work.
A “User Product” is either (1) a “consumer product”, which means
any tangible personal property which is normally used for personal,
family, or household purposes, or (2) anything designed or sold for
incorporation into a dwelling. In determining whether a product is
a consumer product, doubtful cases shall be resolved in favor of
coverage. For a particular product received by a particular user,
“normally used” refers to a typical or common use of that class of
product, regardless of the status of the particular user or of the
way in which the particular user actually uses, or expects or is
expected to use, the product. A product is a consumer product
regardless of whether the product has substantial commercial,
industrial or non-consumer uses, unless such uses represent the
only significant mode of use of the product.
“Installation Information” for a User Product means any methods,
procedures, authorization keys, or other information required to
install and execute modified versions of a covered work in that
User Product from a modified version of its Corresponding Source.
The information must suffice to ensure that the continued
functioning of the modified object code is in no case prevented or
interfered with solely because modification has been made.
If you convey an object code work under this section in, or with,
or specifically for use in, a User Product, and the conveying
occurs as part of a transaction in which the right of possession
and use of the User Product is transferred to the recipient in
perpetuity or for a fixed term (regardless of how the transaction
is characterized), the Corresponding Source conveyed under this
section must be accompanied by the Installation Information. But
this requirement does not apply if neither you nor any third party
retains the ability to install modified object code on the User
Product (for example, the work has been installed in ROM).
The requirement to provide Installation Information does not
include a requirement to continue to provide support service,
warranty, or updates for a work that has been modified or installed
by the recipient, or for the User Product in which it has been
modified or installed. Access to a network may be denied when the
modification itself materially and adversely affects the operation
of the network or violates the rules and protocols for
communication across the network.
Corresponding Source conveyed, and Installation Information
provided, in accord with this section must be in a format that is
publicly documented (and with an implementation available to the
public in source code form), and must require no special password
or key for unpacking, reading or copying.
7. Additional Terms.
“Additional permissions” are terms that supplement the terms of
this License by making exceptions from one or more of its
conditions. Additional permissions that are applicable to the
entire Program shall be treated as though they were included in
this License, to the extent that they are valid under applicable
law. If additional permissions apply only to part of the Program,
that part may be used separately under those permissions, but the
entire Program remains governed by this License without regard to
the additional permissions.
When you convey a copy of a covered work, you may at your option
remove any additional permissions from that copy, or from any part
of it. (Additional permissions may be written to require their own
removal in certain cases when you modify the work.) You may place
additional permissions on material, added by you to a covered work,
for which you have or can give appropriate copyright permission.
Notwithstanding any other provision of this License, for material
you add to a covered work, you may (if authorized by the copyright
holders of that material) supplement the terms of this License with
terms:
a. Disclaiming warranty or limiting liability differently from
the terms of sections 15 and 16 of this License; or
b. Requiring preservation of specified reasonable legal notices
or author attributions in that material or in the Appropriate
Legal Notices displayed by works containing it; or
c. Prohibiting misrepresentation of the origin of that material,
or requiring that modified versions of such material be marked
in reasonable ways as different from the original version; or
d. Limiting the use for publicity purposes of names of licensors
or authors of the material; or
e. Declining to grant rights under trademark law for use of some
trade names, trademarks, or service marks; or
f. Requiring indemnification of licensors and authors of that
material by anyone who conveys the material (or modified
versions of it) with contractual assumptions of liability to
the recipient, for any liability that these contractual
assumptions directly impose on those licensors and authors.
All other non-permissive additional terms are considered “further
restrictions” within the meaning of section 10. If the Program as
you received it, or any part of it, contains a notice stating that
it is governed by this License along with a term that is a further
restriction, you may remove that term. If a license document
contains a further restriction but permits relicensing or conveying
under this License, you may add to a covered work material governed
by the terms of that license document, provided that the further
restriction does not survive such relicensing or conveying.
If you add terms to a covered work in accord with this section, you
must place, in the relevant source files, a statement of the
additional terms that apply to those files, or a notice indicating
where to find the applicable terms.
Additional terms, permissive or non-permissive, may be stated in
the form of a separately written license, or stated as exceptions;
the above requirements apply either way.
8. Termination.
You may not propagate or modify a covered work except as expressly
provided under this License. Any attempt otherwise to propagate or
modify it is void, and will automatically terminate your rights
under this License (including any patent licenses granted under the
third paragraph of section 11).
However, if you cease all violation of this License, then your
license from a particular copyright holder is reinstated (a)
provisionally, unless and until the copyright holder explicitly and
finally terminates your license, and (b) permanently, if the
copyright holder fails to notify you of the violation by some
reasonable means prior to 60 days after the cessation.
Moreover, your license from a particular copyright holder is
reinstated permanently if the copyright holder notifies you of the
violation by some reasonable means, this is the first time you have
received notice of violation of this License (for any work) from
that copyright holder, and you cure the violation prior to 30 days
after your receipt of the notice.
Termination of your rights under this section does not terminate
the licenses of parties who have received copies or rights from you
under this License. If your rights have been terminated and not
permanently reinstated, you do not qualify to receive new licenses
for the same material under section 10.
9. Acceptance Not Required for Having Copies.
You are not required to accept this License in order to receive or
run a copy of the Program. Ancillary propagation of a covered work
occurring solely as a consequence of using peer-to-peer
transmission to receive a copy likewise does not require
acceptance. However, nothing other than this License grants you
permission to propagate or modify any covered work. These actions
infringe copyright if you do not accept this License. Therefore,
by modifying or propagating a covered work, you indicate your
acceptance of this License to do so.
10. Automatic Licensing of Downstream Recipients.
Each time you convey a covered work, the recipient automatically
receives a license from the original licensors, to run, modify and
propagate that work, subject to this License. You are not
responsible for enforcing compliance by third parties with this
License.
An “entity transaction” is a transaction transferring control of an
organization, or substantially all assets of one, or subdividing an
organization, or merging organizations. If propagation of a
covered work results from an entity transaction, each party to that
transaction who receives a copy of the work also receives whatever
licenses to the work the party’s predecessor in interest had or
could give under the previous paragraph, plus a right to possession
of the Corresponding Source of the work from the predecessor in
interest, if the predecessor has it or can get it with reasonable
efforts.
You may not impose any further restrictions on the exercise of the
rights granted or affirmed under this License. For example, you
may not impose a license fee, royalty, or other charge for exercise
of rights granted under this License, and you may not initiate
litigation (including a cross-claim or counterclaim in a lawsuit)
alleging that any patent claim is infringed by making, using,
selling, offering for sale, or importing the Program or any portion
of it.
11. Patents.
A “contributor” is a copyright holder who authorizes use under this
License of the Program or a work on which the Program is based.
The work thus licensed is called the contributor’s “contributor
version”.
A contributor’s “essential patent claims” are all patent claims
owned or controlled by the contributor, whether already acquired or
hereafter acquired, that would be infringed by some manner,
permitted by this License, of making, using, or selling its
contributor version, but do not include claims that would be
infringed only as a consequence of further modification of the
contributor version. For purposes of this definition, “control”
includes the right to grant patent sublicenses in a manner
consistent with the requirements of this License.
Each contributor grants you a non-exclusive, worldwide,
royalty-free patent license under the contributor’s essential
patent claims, to make, use, sell, offer for sale, import and
otherwise run, modify and propagate the contents of its contributor
version.
In the following three paragraphs, a “patent license” is any
express agreement or commitment, however denominated, not to
enforce a patent (such as an express permission to practice a
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Nothing in this License shall be construed as excluding or limiting
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12. No Surrender of Others’ Freedom.
If conditions are imposed on you (whether by court order, agreement
or otherwise) that contradict the conditions of this License, they
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if you agree to terms that obligate you to collect a royalty for
further conveying from those to whom you convey the Program, the
only way you could satisfy both those terms and this License would
be to refrain entirely from conveying the Program.
13. Use with the GNU Affero General Public License.
Notwithstanding any other provision of this License, you have
permission to link or combine any covered work with a work licensed
under version 3 of the GNU Affero General Public License into a
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covered work, but the special requirements of the GNU Affero
General Public License, section 13, concerning interaction through
a network will apply to the combination as such.
14. Revised Versions of this License.
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new versions will be similar in spirit to the present version, but
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If the Program specifies that a proxy can decide which future
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WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES
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If the disclaimer of warranty and limitation of liability provided
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reviewing courts shall apply local law that most closely
approximates an absolute waiver of all civil liability in
connection with the Program, unless a warranty or assumption of
liability accompanies a copy of the Program in return for a fee.
END OF TERMS AND CONDITIONS
===========================
How to Apply These Terms to Your New Programs
=============================================
If you develop a new program, and you want it to be of the greatest
possible use to the public, the best way to achieve this is to make it
free software which everyone can redistribute and change under these
terms.
To do so, attach the following notices to the program. It is safest
to attach them to the start of each source file to most effectively
state the exclusion of warranty; and each file should have at least the
“copyright” line and a pointer to where the full notice is found.
ONE LINE TO GIVE THE PROGRAM'S NAME AND A BRIEF IDEA OF WHAT IT DOES.
Copyright (C) YEAR NAME OF AUTHOR
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or (at
your option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>.
Also add information on how to contact you by electronic and paper
mail.
If the program does terminal interaction, make it output a short
notice like this when it starts in an interactive mode:
PROGRAM Copyright (C) YEAR NAME OF AUTHOR
This program comes with ABSOLUTELY NO WARRANTY; for details type ‘show w’.
This is free software, and you are welcome to redistribute it
under certain conditions; type ‘show c’ for details.
The hypothetical commands ‘show w’ and ‘show c’ should show the
appropriate parts of the General Public License. Of course, your
program’s commands might be different; for a GUI interface, you would
use an “about box”.
You should also get your employer (if you work as a programmer) or
school, if any, to sign a “copyright disclaimer” for the program, if
necessary. For more information on this, and how to apply and follow
the GNU GPL, see <https://www.gnu.org/licenses/>.
The GNU General Public License does not permit incorporating your
program into proprietary programs. If your program is a subroutine
library, you may consider it more useful to permit linking proprietary
applications with the library. If this is what you want to do, use the
GNU Lesser General Public License instead of this License. But first,
please read <https://www.gnu.org/licenses/why-not-lgpl.html>.

File: dash.info, Node: Index, Prev: GPL, Up: Top
Index
*****
[index]
* Menu:
* !cdr: Destructive operations.
(line 16)
* !cons: Destructive operations.
(line 8)
* -->: Threading macros. (line 35)
* ->: Threading macros. (line 9)
* ->>: Threading macros. (line 22)
* -all?: Predicates. (line 53)
* -andfn: Function combinators.
(line 184)
* -annotate: Maps. (line 86)
* -any?: Predicates. (line 41)
* -applify: Function combinators.
(line 63)
* -as->: Threading macros. (line 49)
* -butlast: Other list operations.
(line 405)
* -clone: Tree operations. (line 123)
* -common-prefix: Reductions. (line 242)
* -common-suffix: Reductions. (line 252)
* -compose: Function combinators.
(line 49)
* -concat: List to list. (line 23)
* -cons*: Other list operations.
(line 19)
* -cons-pair?: Predicates. (line 154)
* -const: Function combinators.
(line 128)
* -contains?: Predicates. (line 100)
* -copy: Maps. (line 151)
* -count: Reductions. (line 172)
* -cut: Function combinators.
(line 140)
* -cycle: Unfolding. (line 55)
* -difference: Set operations. (line 22)
* -distinct: Set operations. (line 73)
* -dotimes: Side effects. (line 80)
* -doto: Threading macros. (line 99)
* -drop: Sublist selection. (line 149)
* -drop-last: Sublist selection. (line 163)
* -drop-while: Sublist selection. (line 194)
* -each: Side effects. (line 8)
* -each-indexed: Side effects. (line 38)
* -each-r: Side effects. (line 52)
* -each-r-while: Side effects. (line 65)
* -each-while: Side effects. (line 24)
* -elem-index: Indexing. (line 9)
* -elem-indices: Indexing. (line 23)
* -every: Predicates. (line 23)
* -fifth-item: Other list operations.
(line 380)
* -filter: Sublist selection. (line 8)
* -find-index: Indexing. (line 35)
* -find-indices: Indexing. (line 73)
* -find-last-index: Indexing. (line 54)
* -first: Other list operations.
(line 300)
* -first-item: Other list operations.
(line 328)
* -fix: Other list operations.
(line 445)
* -fixfn: Function combinators.
(line 224)
* -flatten: List to list. (line 38)
* -flatten-n: List to list. (line 60)
* -flip: Function combinators.
(line 95)
* -fourth-item: Other list operations.
(line 367)
* -frequencies: Reductions. (line 310)
* -grade-down: Indexing. (line 103)
* -grade-up: Indexing. (line 93)
* -group-by: Partitioning. (line 205)
* -if-let: Binding. (line 34)
* -if-let*: Binding. (line 45)
* -inits: Reductions. (line 222)
* -insert-at: List to list. (line 114)
* -interleave: Other list operations.
(line 56)
* -interpose: Other list operations.
(line 46)
* -intersection: Set operations. (line 36)
* -iota: Other list operations.
(line 67)
* -is-infix?: Predicates. (line 140)
* -is-prefix?: Predicates. (line 116)
* -is-suffix?: Predicates. (line 128)
* -iterate: Unfolding. (line 9)
* -iteratefn: Function combinators.
(line 201)
* -juxt: Function combinators.
(line 37)
* -keep: List to list. (line 8)
* -lambda: Binding. (line 247)
* -last: Other list operations.
(line 318)
* -last-item: Other list operations.
(line 393)
* -let: Binding. (line 61)
* -let*: Binding. (line 227)
* -list: Other list operations.
(line 428)
* -map: Maps. (line 10)
* -map-first: Maps. (line 38)
* -map-indexed: Maps. (line 68)
* -map-last: Maps. (line 53)
* -map-when: Maps. (line 22)
* -mapcat: Maps. (line 140)
* -max: Reductions. (line 286)
* -max-by: Reductions. (line 296)
* -min: Reductions. (line 262)
* -min-by: Reductions. (line 272)
* -non-nil: Sublist selection. (line 95)
* -none?: Predicates. (line 73)
* -not: Function combinators.
(line 153)
* -on: Function combinators.
(line 75)
* -only-some?: Predicates. (line 85)
* -orfn: Function combinators.
(line 167)
* -pad: Other list operations.
(line 241)
* -partial: Function combinators.
(line 8)
* -partition: Partitioning. (line 90)
* -partition-after-item: Partitioning. (line 195)
* -partition-after-pred: Partitioning. (line 162)
* -partition-all: Partitioning. (line 102)
* -partition-all-in-steps: Partitioning. (line 126)
* -partition-before-item: Partitioning. (line 185)
* -partition-before-pred: Partitioning. (line 174)
* -partition-by: Partitioning. (line 138)
* -partition-by-header: Partitioning. (line 149)
* -partition-in-steps: Partitioning. (line 113)
* -permutations: Set operations. (line 60)
* -powerset: Set operations. (line 50)
* -prodfn: Function combinators.
(line 258)
* -product: Reductions. (line 201)
* -reduce: Reductions. (line 53)
* -reduce-from: Reductions. (line 8)
* -reduce-r: Reductions. (line 72)
* -reduce-r-from: Reductions. (line 26)
* -reductions: Reductions. (line 136)
* -reductions-from: Reductions. (line 100)
* -reductions-r: Reductions. (line 154)
* -reductions-r-from: Reductions. (line 118)
* -remove: Sublist selection. (line 26)
* -remove-at: List to list. (line 151)
* -remove-at-indices: List to list. (line 170)
* -remove-first: Sublist selection. (line 44)
* -remove-item: Sublist selection. (line 84)
* -remove-last: Sublist selection. (line 65)
* -repeat: Unfolding. (line 44)
* -replace: List to list. (line 72)
* -replace-at: List to list. (line 125)
* -replace-first: List to list. (line 86)
* -replace-last: List to list. (line 100)
* -rotate: Other list operations.
(line 8)
* -rotate-args: Function combinators.
(line 112)
* -rpartial: Function combinators.
(line 22)
* -running-product: Reductions. (line 211)
* -running-sum: Reductions. (line 190)
* -same-items?: Set operations. (line 88)
* -second-item: Other list operations.
(line 341)
* -select-by-indices: Sublist selection. (line 211)
* -select-column: Sublist selection. (line 241)
* -select-columns: Sublist selection. (line 222)
* -separate: Partitioning. (line 75)
* -setq: Binding. (line 270)
* -slice: Sublist selection. (line 105)
* -snoc: Other list operations.
(line 32)
* -some: Predicates. (line 8)
* -some-->: Threading macros. (line 86)
* -some->: Threading macros. (line 62)
* -some->>: Threading macros. (line 74)
* -sort: Other list operations.
(line 415)
* -splice: Maps. (line 102)
* -splice-list: Maps. (line 127)
* -split-at: Partitioning. (line 8)
* -split-on: Partitioning. (line 40)
* -split-when: Partitioning. (line 58)
* -split-with: Partitioning. (line 23)
* -sum: Reductions. (line 180)
* -table: Other list operations.
(line 256)
* -table-flat: Other list operations.
(line 275)
* -tails: Reductions. (line 232)
* -take: Sublist selection. (line 121)
* -take-last: Sublist selection. (line 135)
* -take-while: Sublist selection. (line 177)
* -third-item: Other list operations.
(line 354)
* -tree-map: Tree operations. (line 28)
* -tree-map-nodes: Tree operations. (line 39)
* -tree-mapreduce: Tree operations. (line 85)
* -tree-mapreduce-from: Tree operations. (line 104)
* -tree-reduce: Tree operations. (line 53)
* -tree-reduce-from: Tree operations. (line 70)
* -tree-seq: Tree operations. (line 8)
* -unfold: Unfolding. (line 25)
* -union: Set operations. (line 8)
* -unzip: Other list operations.
(line 215)
* -unzip-lists: Other list operations.
(line 196)
* -update-at: List to list. (line 137)
* -when-let: Binding. (line 9)
* -when-let*: Binding. (line 21)
* -zip: Other list operations.
(line 150)
* -zip-fill: Other list operations.
(line 176)
* -zip-lists: Other list operations.
(line 114)
* -zip-lists-fill: Other list operations.
(line 135)
* -zip-pair: Other list operations.
(line 98)
* -zip-with: Other list operations.
(line 80)
* dash-fontify-mode: Fontification of special variables.
(line 6)
* dash-register-info-lookup: Info symbol lookup. (line 6)
* global-dash-fontify-mode: Fontification of special variables.
(line 12)

Tag Table:
Node: Top742
Node: Installation2397
Node: Using in a package3159
Node: Fontification of special variables3504
Node: Info symbol lookup4294
Node: Functions4877
Node: Maps6361
Ref: -map6658
Ref: -map-when7031
Ref: -map-first7605
Ref: -map-last8200
Ref: -map-indexed8790
Ref: -annotate9476
Ref: -splice10080
Ref: -splice-list11155
Ref: -mapcat11614
Ref: -copy11987
Node: Sublist selection12175
Ref: -filter12368
Ref: -remove12921
Ref: -remove-first13470
Ref: -remove-last14318
Ref: -remove-item15048
Ref: -non-nil15448
Ref: -slice15730
Ref: -take16259
Ref: -take-last16677
Ref: -drop17114
Ref: -drop-last17561
Ref: -take-while17993
Ref: -drop-while18620
Ref: -select-by-indices19253
Ref: -select-columns19764
Ref: -select-column20467
Node: List to list20930
Ref: -keep21122
Ref: -concat21698
Ref: -flatten22226
Ref: -flatten-n22988
Ref: -replace23372
Ref: -replace-first23833
Ref: -replace-last24328
Ref: -insert-at24816
Ref: -replace-at25141
Ref: -update-at25528
Ref: -remove-at26069
Ref: -remove-at-indices26696
Node: Reductions27386
Ref: -reduce-from27582
Ref: -reduce-r-from28306
Ref: -reduce29569
Ref: -reduce-r30320
Ref: -reductions-from31598
Ref: -reductions-r-from32404
Ref: -reductions33234
Ref: -reductions-r33945
Ref: -count34690
Ref: -sum34920
Ref: -running-sum35108
Ref: -product35429
Ref: -running-product35637
Ref: -inits35978
Ref: -tails36223
Ref: -common-prefix36468
Ref: -common-suffix36762
Ref: -min37056
Ref: -min-by37282
Ref: -max37803
Ref: -max-by38028
Ref: -frequencies38554
Node: Unfolding39169
Ref: -iterate39410
Ref: -unfold39857
Ref: -repeat40662
Ref: -cycle40946
Node: Predicates41343
Ref: -some41520
Ref: -every41949
Ref: -any?42663
Ref: -all?43012
Ref: -none?43754
Ref: -only-some?44074
Ref: -contains?44619
Ref: -is-prefix?45125
Ref: -is-suffix?45457
Ref: -is-infix?45789
Ref: -cons-pair?46149
Node: Partitioning46480
Ref: -split-at46668
Ref: -split-with47332
Ref: -split-on47972
Ref: -split-when48643
Ref: -separate49286
Ref: -partition49820
Ref: -partition-all50269
Ref: -partition-in-steps50694
Ref: -partition-all-in-steps51240
Ref: -partition-by51754
Ref: -partition-by-header52132
Ref: -partition-after-pred52733
Ref: -partition-before-pred53186
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Node: Indexing54613
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Ref: -union58847
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Ref: -powerset60134
Ref: -permutations60411
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Node: Other list operations61852
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Ref: -zip-lists65781
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End Tag Table

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