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This is dash.info, produced by makeinfo version 6.5 from dash.texi.
This manual is for ‘dash.el’ version 2.12.1.
Copyright © 2012-2015 Magnar Sveen
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
<http://www.gnu.org/licenses/>.
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.el’ version 2.12.1.
Copyright © 2012-2015 Magnar Sveen
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
<http://www.gnu.org/licenses/>.
* Menu:
* Installation::
* Functions::
* Development::
* Index::
— The Detailed Node Listing —
Installation
* Using in a package::
* Fontification of special variables::
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
* Changes:: List of significant changes by version
* Contributors:: List of contributors

File: dash.info, Node: Installation, Next: Functions, Prev: Top, Up: Top
1 Installation
**************
It’s available on GNU ELPA (https://elpa.gnu.org/) and MELPA
(https://melpa.org/); use ‘M-x package-install’:
‘M-x package-install <RET> dash’
Install the dash library.
‘M-x package-install <RET> dash-functional’
Optional, if you want the function combinators.
Alternatively, you can just dump dash.el or dash-functional.el in
your load path somewhere.
* Menu:
* Using in a package::
* Fontification of special variables::

File: dash.info, Node: Using in a package, Next: Fontification of special variables, Up: Installation
1.1 Using in a package
======================
Add this to the big comment block at the top:
;; Package-Requires: ((dash "2.12.1"))
To get function combinators:
;; Package-Requires: ((dash "2.12.1") (dash-functional "1.2.0") (emacs "24"))

File: dash.info, Node: Fontification of special variables, Prev: Using in a package, Up: Installation
1.2 Fontification of special variables
======================================
Font lock of special Dash variables (‘it’, ‘acc’, etc.) in Emacs Lisp
buffers can optionally be enabled with the autoloaded minor mode
‘dash-fontify-mode’. In older Emacs versions which do not dynamically
detect macros, the minor mode also fontifies Dash macro calls.
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: Functions, Next: Development, Prev: Installation, Up: Top
2 Functions
***********
This chapter contains reference documentation for the dash application
programming interface (API). All functions and constructs in the library
are prefixed with a dash (-).
There are also anaphoric versions of functions where that makes
sense, prefixed with two dashes instead of one.
For instance, while ‘-map’ takes a function to map over the list, one
can also use the anaphoric form with double dashes - which will then be
executed with ‘it’ exposed as the list item. Here’s an example:
(-map (lambda (n) (* n n)) '(1 2 3 4)) ;; normal version
(--map (* it it) '(1 2 3 4)) ;; anaphoric version
Of course, the original can also be written like
(defun square (n) (* n n))
(-map 'square '(1 2 3 4))
which demonstrates the usefulness of both versions.
* 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 new list.
-- Function: -map (fn list)
Return a new list consisting of the result of applying FN to the
items in LIST.
(-map (lambda (num) (* num num)) '(1 2 3 4))
⇒ '(1 4 9 16)
(-map 'square '(1 2 3 4))
⇒ '(1 4 9 16)
(--map (* it it) '(1 2 3 4))
⇒ '(1 4 9 16)
-- Function: -map-when (pred rep list)
Return a new list where the elements in LIST that do not match the
PRED function are unchanged, and where the elements in LIST that do
match the PRED function 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)
Replace first item in LIST satisfying PRED with result of REP
called on this 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)
Replace last item in LIST satisfying PRED with result of REP called
on this 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)
Return a new list consisting of the result of (FN index item) for
each item in LIST.
In the anaphoric form ‘--map-indexed’, the index is exposed as
symbol ‘it-index’.
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)
-- Function: -annotate (fn list)
Return a list of cons cells where each cell is FN applied to each
element of LIST paired with the unmodified element of LIST.
(-annotate '1+ '(1 2 3))
⇒ '((2 . 1) (3 . 2) (4 . 3))
(-annotate 'length '(("h" "e" "l" "l" "o") ("hello" "world")))
⇒ '((5 "h" "e" "l" "l" "o") (2 "hello" "world"))
(--annotate (< 1 it) '(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 elements matching PRED in
LIST.
FUN takes the element matching PRED as input.
This function can be used as replacement for ‘,@’ in case you need
to splice several lists at marked positions (for example with
keywords).
See also: ‘-splice-list’ (*note -splice-list::), ‘-insert-at’
(*note -insert-at::)
(-splice 'even? (lambda (x) (list x x)) '(1 2 3 4))
⇒ '(1 2 2 3 4 4)
(--splice 't (list it it) '(1 2 3 4))
⇒ '(1 1 2 2 3 3 4 4)
(--splice (equal it :magic) '((list of) (magical) (code)) '((foo) (bar) :magic (baz)))
⇒ '((foo) (bar) (list of) (magical) (code) (baz))
-- 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 (arg)
Create a shallow copy of LIST.
(fn 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 a
non-nil value.
Alias: ‘-select’
See also: ‘-keep’ (*note -keep::), ‘-remove’ (*note -remove::).
(-filter (lambda (num) (= 0 (% num 2))) '(1 2 3 4))
⇒ '(2 4)
(-filter 'even? '(1 2 3 4))
⇒ '(2 4)
(--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’
See also: ‘-filter’ (*note -filter::).
(-remove (lambda (num) (= 0 (% num 2))) '(1 2 3 4))
⇒ '(1 3)
(-remove 'even? '(1 2 3 4))
⇒ '(1 3)
(--remove (= 0 (% it 2)) '(1 2 3 4))
⇒ '(1 3)
-- Function: -remove-first (pred list)
Return a new list with the first item matching PRED removed.
Alias: ‘-reject-first’
See also: ‘-remove’ (*note -remove::), ‘-map-first’ (*note
-map-first::)
(-remove-first 'even? '(1 3 5 4 7 8 10))
⇒ '(1 3 5 7 8 10)
(-remove-first 'stringp '(1 2 "first" "second" "third"))
⇒ '(1 2 "second" "third")
(--remove-first (> it 3) '(1 2 3 4 5 6 7 8 9 10))
⇒ '(1 2 3 5 6 7 8 9 10)
-- Function: -remove-last (pred list)
Return a new list with the last item matching PRED removed.
Alias: ‘-reject-last’
See also: ‘-remove’ (*note -remove::), ‘-map-last’ (*note
-map-last::)
(-remove-last 'even? '(1 3 5 4 7 8 10 11))
⇒ '(1 3 5 4 7 8 11)
(-remove-last 'stringp '(1 2 "last" "second" "third"))
⇒ '(1 2 "last" "second")
(--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)
Remove all occurrences of ITEM from LIST.
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" "dave"))
⇒ '("alice" "eve" "dave")
-- Function: -non-nil (list)
Return all non-nil elements of LIST.
(-non-nil '(1 nil 2 nil nil 3 4 nil 5 nil))
⇒ '(1 2 3 4 5)
-- 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 new list of the first N items in LIST, or all items if
there are fewer than N.
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)
-- Function: -take-last (n list)
Return the last N items of LIST in order.
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 of LIST without the first N items.
See also: ‘-drop-last’ (*note -drop-last::)
(fn N LIST)
(-drop 3 '(1 2 3 4 5))
⇒ '(4 5)
(-drop 17 '(1 2 3 4 5))
⇒ '()
-- Function: -drop-last (n list)
Remove the last N items of LIST and return a copy.
See also: ‘-drop’ (*note -drop::)
(-drop-last 3 '(1 2 3 4 5))
⇒ '(1 2)
(-drop-last 17 '(1 2 3 4 5))
⇒ '()
-- Function: -take-while (pred list)
Return a new list of successive items from LIST while (PRED item)
returns a non-nil value.
(-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)
Return the tail of LIST starting from the first item for which
(PRED item) returns nil.
(-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 the
items in LIST.
If you want to select the original items satisfying a predicate use
‘-filter’ (*note -filter::).
(-keep 'cdr '((1 2 3) (4 5) (6)))
⇒ '((2 3) (5))
(-keep (lambda (num) (when (> num 3) (* 10 num))) '(1 2 3 4 5 6))
⇒ '(40 50 60)
(--keep (when (> it 3) (* 10 it)) '(1 2 3 4 5 6))
⇒ '(40 50 60)
-- Function: -concat (&rest lists)
Return a new list with the concatenation of the elements in the
supplied LISTS.
(-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)
Return a list with element at Nth position in LIST replaced with
‘(func (nth n list))‘.
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 a list with element at Nth position in LIST removed.
See also: ‘-remove-at-indices’ (*note -remove-at-indices::),
‘-remove’ (*note -remove::)
(-remove-at 0 '("0" "1" "2" "3" "4" "5"))
⇒ '("1" "2" "3" "4" "5")
(-remove-at 1 '("0" "1" "2" "3" "4" "5"))
⇒ '("0" "2" "3" "4" "5")
(-remove-at 2 '("0" "1" "2" "3" "4" "5"))
⇒ '("0" "1" "3" "4" "5")
-- Function: -remove-at-indices (indices list)
Return a list whose elements are elements from LIST without
elements selected as ‘(nth i list)‘ for all i from INDICES.
See also: ‘-remove-at’ (*note -remove-at::), ‘-remove’ (*note
-remove::)
(-remove-at-indices '(0) '("0" "1" "2" "3" "4" "5"))
⇒ '("1" "2" "3" "4" "5")
(-remove-at-indices '(0 2 4) '("0" "1" "2" "3" "4" "5"))
⇒ '("1" "3" "5")
(-remove-at-indices '(0 5) '("0" "1" "2" "3" "4" "5"))
⇒ '("1" "2" "3" "4")

File: dash.info, Node: Reductions, Next: Unfolding, Prev: List to list, Up: Functions
2.4 Reductions
==============
Functions reducing lists into single value.
-- Function: -reduce-from (fn initial-value list)
Return the result of applying FN to INITIAL-VALUE and the first
item in LIST, then applying FN to that result and the 2nd item,
etc. If LIST contains no items, return INITIAL-VALUE and do not
call FN.
In the anaphoric form ‘--reduce-from’, the accumulated value is
exposed as symbol ‘acc’.
See also: ‘-reduce’ (*note -reduce::), ‘-reduce-r’ (*note
-reduce-r::)
(-reduce-from '- 10 '(1 2 3))
⇒ 4
(-reduce-from (lambda (memo item) (format "(%s - %d)" memo item)) "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 initial-value list)
Replace conses with FN, nil with INITIAL-VALUE and evaluate the
resulting expression. If LIST is empty, INITIAL-VALUE is returned
and FN is not called.
Note: this function works the same as ‘-reduce-from’ (*note
-reduce-from::) but the operation associates from right instead of
from left.
See also: ‘-reduce-r’ (*note -reduce-r::), ‘-reduce’ (*note
-reduce::)
(-reduce-r-from '- 10 '(1 2 3))
⇒ -8
(-reduce-r-from (lambda (item memo) (format "(%d - %s)" item memo)) "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)
Return the result of applying FN to the first 2 items in LIST, then
applying FN to that result and the 3rd item, etc. If LIST contains
no items, return the result of calling FN with no arguments. If
LIST contains a single item, return that item and do not call FN.
In the anaphoric form ‘--reduce’, the accumulated value is exposed
as symbol ‘acc’.
See also: ‘-reduce-from’ (*note -reduce-from::), ‘-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)
Replace conses with FN and evaluate the resulting expression. The
final nil is ignored. If LIST contains no items, return the result
of calling FN with no arguments. If LIST contains a single item,
return that item and do not call FN.
The first argument of FN is the new item, the second is the
accumulated value.
Note: this function works the same as ‘-reduce’ (*note -reduce::)
but the operation associates from right instead of from left.
See also: ‘-reduce-r-from’ (*note -reduce-r-from::), ‘-reduce’
(*note -reduce::)
(-reduce-r '- '(1 2 3 4))
⇒ -2
(-reduce-r (lambda (item memo) (format "%s-%d" memo item)) '(1 2 3))
⇒ "3-2-1"
(--reduce-r (format "%s-%d" acc it) '(1 2 3))
⇒ "3-2-1"
-- Function: -reductions-from (fn init list)
Return a list of the intermediate values of the reduction.
See ‘-reduce-from’ (*note -reduce-from::) for explanation of the
arguments.
See also: ‘-reductions’ (*note -reductions::), ‘-reductions-r’
(*note -reductions-r::), ‘-reduce-r’ (*note -reduce-r::)
(-reductions-from (lambda (a i) (format "(%s FN %d)" a i)) "INIT" '(1 2 3 4))
⇒ '("INIT" "(INIT FN 1)" "((INIT FN 1) FN 2)" "(((INIT FN 1) FN 2) FN 3)" "((((INIT FN 1) FN 2) FN 3) FN 4)")
(-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)
-- Function: -reductions-r-from (fn init list)
Return a list of the intermediate values of the reduction.
See ‘-reduce-r-from’ (*note -reduce-r-from::) for explanation of
the arguments.
See also: ‘-reductions-r’ (*note -reductions-r::), ‘-reductions’
(*note -reductions::), ‘-reduce’ (*note -reduce::)
(-reductions-r-from (lambda (i a) (format "(%d FN %s)" i a)) "INIT" '(1 2 3 4))
⇒ '("(1 FN (2 FN (3 FN (4 FN INIT))))" "(2 FN (3 FN (4 FN INIT)))" "(3 FN (4 FN INIT))" "(4 FN INIT)" "INIT")
(-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)
-- Function: -reductions (fn list)
Return a list of the intermediate values of the reduction.
See ‘-reduce’ (*note -reduce::) for explanation of the arguments.
See also: ‘-reductions-from’ (*note -reductions-from::),
‘-reductions-r’ (*note -reductions-r::), ‘-reduce-r’ (*note
-reduce-r::)
(-reductions (lambda (a i) (format "(%s FN %d)" a i)) '(1 2 3 4))
⇒ '(1 "(1 FN 2)" "((1 FN 2) FN 3)" "(((1 FN 2) FN 3) FN 4)")
(-reductions '+ '(1 2 3 4))
⇒ '(1 3 6 10)
(-reductions '* '(1 2 3 4))
⇒ '(1 2 6 24)
-- Function: -reductions-r (fn list)
Return a list of the intermediate values of the reduction.
See ‘-reduce-r’ (*note -reduce-r::) for explanation of the
arguments.
See also: ‘-reductions-r-from’ (*note -reductions-r-from::),
‘-reductions’ (*note -reductions::), ‘-reduce’ (*note -reduce::)
(-reductions-r (lambda (i a) (format "(%d FN %s)" i a)) '(1 2 3 4))
⇒ '("(1 FN (2 FN (3 FN 4)))" "(2 FN (3 FN 4))" "(3 FN 4)" 4)
(-reductions-r '+ '(1 2 3 4))
⇒ '(10 9 7 4)
(-reductions-r '* '(1 2 3 4))
⇒ '(24 24 12 4)
-- 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
-- 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
-- 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))
⇒ nil
(-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))
⇒ nil
(-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)

File: dash.info, Node: Unfolding, Next: Predicates, Prev: Reductions, Up: Functions
2.5 Unfolding
=============
Operations dual to reductions, building lists from 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 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))

File: dash.info, Node: Predicates, Next: Partitioning, Prev: Unfolding, Up: Functions
2.6 Predicates
==============
-- 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? 'even? '(1 2 3))
⇒ t
(-any? 'even? '(1 3 5))
⇒ 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.
Alias: ‘-all-p’, ‘-every?’, ‘-every-p’
(-all? 'even? '(1 2 3))
⇒ nil
(-all? 'even? '(2 4 6))
⇒ t
(--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 at least one item of LIST matches PRED and at least
one item of LIST does not match PRED. Return ‘nil‘ both if all
items match the predicate or if none of the items match the
predicate.
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’s non-nil.
Alias: ‘-contains-p’
(-contains? '(1 2 3) 1)
⇒ t
(-contains? '(1 2 3) 2)
⇒ t
(-contains? '(1 2 3) 4)
⇒ nil
-- Function: -same-items? (list list2)
Return true if LIST and LIST2 has the same items.
The order of the elements in the lists does not matter.
Alias: ‘-same-items-p’
(-same-items? '(1 2 3) '(1 2 3))
⇒ t
(-same-items? '(1 2 3) '(3 2 1))
⇒ t
(-same-items? '(1 2 3) '(1 2 3 4))
⇒ nil
-- Function: -is-prefix? (prefix list)
Return non-nil if PREFIX is 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 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

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)
Return a list of ((-take N LIST) (-drop N LIST)), in no more than
one pass through the list.
(-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)
-- Function: -split-with (pred list)
Return a list of ((-take-while PRED LIST) (-drop-while PRED LIST)),
in no more than one pass through the 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)
Return a list of ((-filter PRED LIST) (-remove PRED LIST)), in one
pass through the 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)
Return a new list with the items in LIST grouped into N-sized
sublists at offsets STEP apart. 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)
Return a new list with the items in LIST grouped into N-sized
sublists at offsets STEP apart. The last 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 directly after each time PRED is true on an element of
LIST.
(-partition-after-pred #'odd? '())
⇒ '()
(-partition-after-pred #'odd? '(1))
⇒ '((1))
(-partition-after-pred #'odd? '(0 1))
⇒ '((0 1))
-- Function: -partition-before-pred (pred list)
Partition directly before each time PRED is true on an element of
LIST.
(-partition-before-pred #'odd? '())
⇒ '()
(-partition-before-pred #'odd? '(1))
⇒ '((1))
(-partition-before-pred #'odd? '(0 1))
⇒ '((0) (1))
-- 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
============
Return indices of elements based on predicates, sort elements by indices
etc.
-- Function: -elem-index (elem list)
Return the index of the first element in the given LIST which is
equal to the query element ELEM, or nil if there is no such
element.
(-elem-index 2 '(6 7 8 2 3 4))
⇒ 3
(-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 indices of all elements in LIST equal to the query
element ELEM, in ascending order.
(-elem-indices 2 '(6 7 8 2 3 4 2 1))
⇒ '(3 6)
(-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)
Take a predicate PRED and a LIST and return the index of the first
element in the list satisfying the predicate, or nil if there is no
such element.
See also ‘-first’ (*note -first::).
(-find-index 'even? '(2 4 1 6 3 3 5 8))
⇒ 0
(--find-index (< 5 it) '(2 4 1 6 3 3 5 8))
⇒ 3
(-find-index (-partial 'string-lessp "baz") '("bar" "foo" "baz"))
⇒ 1
-- Function: -find-last-index (pred list)
Take a predicate PRED and a LIST and return the index of the last
element in the list satisfying the predicate, or nil if there is no
such element.
See also ‘-last’ (*note -last::).
(-find-last-index 'even? '(2 4 1 6 3 3 5 8))
⇒ 7
(--find-last-index (< 5 it) '(2 7 1 6 3 8 5 2))
⇒ 5
(-find-last-index (-partial 'string-lessp "baz") '("q" "foo" "baz"))
⇒ 1
-- Function: -find-indices (pred list)
Return the indices of all elements in LIST satisfying the predicate
PRED, in ascending order.
(-find-indices 'even? '(2 4 1 6 3 3 5 8))
⇒ '(0 1 3 7)
(--find-indices (< 5 it) '(2 4 1 6 3 3 5 8))
⇒ '(3 7)
(-find-indices (-partial 'string-lessp "baz") '("bar" "foo" "baz"))
⇒ '(1)
-- Function: -grade-up (comparator list)
Grade elements of LIST using COMPARATOR relation, yielding 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, yielding 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 (list list2)
Return a new list containing the elements of LIST and elements of
LIST2 that are not in LIST. The test for equality is done with
‘equal’, or with ‘-compare-fn’ if that’s non-nil.
(-union '(1 2 3) '(3 4 5))
⇒ '(1 2 3 4 5)
(-union '(1 2 3 4) '())
⇒ '(1 2 3 4)
(-union '(1 1 2 2) '(3 2 1))
⇒ '(1 1 2 2 3)
-- Function: -difference (list list2)
Return a new list with only the members of LIST that are not in
LIST2. The test for equality is done with ‘equal’, or with
‘-compare-fn’ if that’s 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 (list list2)
Return a new list containing only the elements that are members of
both LIST and LIST2. The test for equality is done with ‘equal’,
or with ‘-compare-fn’ if that’s non-nil.
(-intersection '() '())
⇒ '()
(-intersection '(1 2 3) '(4 5 6))
⇒ '()
(-intersection '(1 2 3 4) '(3 4 5 6))
⇒ '(3 4)
-- Function: -powerset (list)
Return the power set of LIST.
(-powerset '())
⇒ '(nil)
(-powerset '(x y z))
⇒ '((x y z) (x y) (x z) (x) (y z) (y) (z) nil)
-- Function: -permutations (list)
Return the permutations of LIST.
(-permutations '())
⇒ '(nil)
(-permutations '(1 2))
⇒ '((1 2) (2 1))
(-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 new list with all duplicates removed. The test for
equality is done with ‘equal’, or with ‘-compare-fn’ if that’s
non-nil.
Alias: ‘-uniq’
(-distinct '())
⇒ '()
(-distinct '(1 2 2 4))
⇒ '(1 2 4)
(-distinct '(t t t))
⇒ '(t)

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. With N negative, rotate to the
left. 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: -repeat (n x)
Return a list with X repeated N times. Return nil if N is less
than 1.
(-repeat 3 :a)
⇒ '(:a :a :a)
(-repeat 1 :a)
⇒ '(:a)
(-repeat 0 :a)
⇒ nil
-- Function: -cons* (&rest args)
Make a new list from the elements of ARGS.
The last 2 members of ARGS are used as the final cons of the result
so if the final member of ARGS is not a list the result is a dotted
list.
(-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 ELEMENTS is non nil, append these 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: -zip-with (fn list1 list2)
Zip the two lists LIST1 and LIST2 using a function FN. This
function is applied pairwise taking as first argument element of
LIST1 and as second argument element of LIST2 at corresponding
position.
The anaphoric form ‘--zip-with’ binds the elements from LIST1 as
symbol ‘it’, and the elements from LIST2 as symbol ‘other’.
(-zip-with '+ '(1 2 3) '(4 5 6))
⇒ '(5 7 9)
(-zip-with 'cons '(1 2 3) '(4 5 6))
⇒ '((1 . 4) (2 . 5) (3 . 6))
(--zip-with (concat it " and " other) '("Batman" "Jekyll") '("Robin" "Hyde"))
⇒ '("Batman and Robin" "Jekyll and Hyde")
-- Function: -zip (&rest lists)
Zip LISTS together. Group the head of each list, followed by the
second elements of each list, and so on. The lengths of the
returned groupings are equal to the length of the shortest input
list.
If two lists are provided as arguments, return the groupings as a
list of cons cells. Otherwise, return the groupings as a list of
lists.
Use ‘-zip-lists’ (*note -zip-lists::) if you need the return value
to always be a list of lists.
Alias: ‘-zip-pair’
See also: ‘-zip-lists’ (*note -zip-lists::)
(-zip '(1 2 3) '(4 5 6))
⇒ '((1 . 4) (2 . 5) (3 . 6))
(-zip '(1 2 3) '(4 5 6 7))
⇒ '((1 . 4) (2 . 5) (3 . 6))
(-zip '(1 2) '(3 4 5) '(6))
⇒ '((1 3 6))
-- Function: -zip-lists (&rest lists)
Zip LISTS together. Group the head of each list, followed by the
second elements of each list, and so on. The lengths of the
returned groupings are equal to the length of the shortest input
list.
The return value is always list of lists, which is a difference
from ‘-zip-pair’ which returns a cons-cell in case two input lists
are provided.
See also: ‘-zip’ (*note -zip::)
(-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-fill (fill-value &rest lists)
Zip LISTS, with FILL-VALUE padded onto the shorter lists. The
lengths of the returned groupings are equal to the length of the
longest input list.
(-zip-fill 0 '(1 2 3 4 5) '(6 7 8 9))
⇒ '((1 . 6) (2 . 7) (3 . 8) (4 . 9) (5 . 0))
-- Function: -unzip (lists)
Unzip LISTS.
This works just like ‘-zip’ (*note -zip::) 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 the same length).
Note in particular that calling this on a list of two lists will
return a list of cons-cells such that the above identity works.
See also: ‘-zip’ (*note -zip::)
(-unzip (-zip '(1 2 3) '(a b c) '("e" "f" "g")))
⇒ '((1 2 3) (a b c) ("e" "f" "g"))
(-unzip '((1 2) (3 4) (5 6) (7 8) (9 10)))
⇒ '((1 3 5 7 9) (2 4 6 8 10))
(-unzip '((1 2) (3 4)))
⇒ '((1 . 3) (2 . 4))
-- 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 (-cycle '(1 2 3)) '(1 2))
⇒ '((1 . 1) (2 . 2))
-- Function: -pad (fill-value &rest lists)
Appends FILL-VALUE to the end of each list in LISTS such that they
will all have the same length.
(-pad 0 '())
⇒ '(nil)
(-pad 0 '(1))
⇒ '((1))
(-pad 0 '(1 2 3) '(4 5))
⇒ '((1 2 3) (4 5 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 x in LIST where (PRED x) is non-nil, else nil.
To get the first item in the list no questions asked, use ‘car’.
Alias: ‘-find’
(-first 'even? '(1 2 3))
⇒ 2
(-first 'even? '(1 3 5))
⇒ nil
(-first 'null '(1 3 5))
⇒ nil
-- Function: -some (pred list)
Return (PRED x) for the first LIST item where (PRED x) is non-nil,
else nil.
Alias: ‘-any’
(-some 'even? '(1 2 3))
⇒ t
(-some 'null '(1 2 3))
⇒ nil
(-some 'null '(1 2 nil))
⇒ t
-- 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::).
(fn LIST)
(-first-item '(1 2 3))
⇒ 1
(-first-item nil)
⇒ nil
(let ((list (list 1 2 3))) (setf (-first-item list) 5) list)
⇒ '(5 2 3)
-- Function: -second-item (arg1)
Return the second item of LIST, or nil if LIST is too short.
See also: ‘-third-item’ (*note -third-item::).
(fn LIST)
(-second-item '(1 2 3))
⇒ 2
(-second-item nil)
⇒ nil
-- Function: -third-item (arg1)
Return the third item of LIST, or nil if LIST is too short.
See also: ‘-fourth-item’ (*note -fourth-item::).
(fn LIST)
(-third-item '(1 2 3))
⇒ 3
(-third-item nil)
⇒ nil
-- Function: -fourth-item (list)
Return the fourth item of LIST, or nil if LIST is too short.
See also: ‘-fifth-item’ (*note -fifth-item::).
(-fourth-item '(1 2 3 4))
⇒ 4
(-fourth-item nil)
⇒ nil
-- Function: -fifth-item (list)
Return the fifth item of LIST, or nil if LIST is too short.
See also: ‘-last-item’ (*note -last-item::).
(-fifth-item '(1 2 3 4 5))
⇒ 5
(-fifth-item nil)
⇒ nil
-- Function: -last-item (list)
Return the last item of LIST, or nil on an empty list.
(-last-item '(1 2 3))
⇒ 3
(-last-item nil)
⇒ nil
(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 (&rest args)
Return a list with ARGS.
If first item of ARGS is already a list, simply return ARGS. If
not, return a list with ARGS as elements.
(-list 1)
⇒ '(1)
(-list 1 2 3)
⇒ '(1 2 3)
(-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 4 5 6)))
⇒ '((1) (2) (3) (4) (5) (6))
(let ((data '(("starwars" "scifi") ("jedi" "starwars" "warrior")))) (--fix (-uniq (--mapcat (cons it (cdr (assoc it data))) 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) "}" '((elips-mode (foo (bar . booze)) (baz . qux)) (c-mode (foo . bla) (bum . bam)))))
⇒ "{elips-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 '(1 2 3)) (b (-clone a))) (nreverse a) b)
⇒ '(1 2 3)

File: dash.info, Node: Threading macros, Next: Binding, Prev: Tree operations, Up: Functions
2.12 Threading macros
=====================
-- 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 in 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--> (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--> "def" (concat "abc" it "ghi"))
⇒ "abcdefghi"
(-some--> nil (concat "abc" it "ghi"))
⇒ nil
(-some--> '(1 3 5) (-filter 'even? it) (append it it) (-map 'square it))
⇒ nil

File: dash.info, Node: Binding, Next: Side-effects, Prev: Threading macros, Up: Functions
2.13 Binding
============
Convenient versions of ‘let‘ and ‘let*‘ constructs combined with 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::).
(fn (VAR VAL) &rest BODY)
(-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::).
(fn (VAR VAL) THEN &rest ELSE)
(-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 the description of 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 (&rest forms)
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.
(fn [MATCH-FORM VAL]...)
(progn (-setq a 1) a)
⇒ 1
(progn (-setq (a b) (list 1 2)) (list a b))
⇒ '(1 2)
(progn (-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 with every item in LIST. Return nil, used for side-effects
only.
(let (s) (-each '(1 2 3) (lambda (item) (setq s (cons item s)))))
⇒ nil
(let (s) (-each '(1 2 3) (lambda (item) (setq s (cons item s)))) s)
⇒ '(3 2 1)
(let (s) (--each '(1 2 3) (setq s (cons it s))) s)
⇒ '(3 2 1)
-- Function: -each-while (list pred fn)
Call FN with every item in LIST while (PRED item) is non-nil.
Return nil, used for side-effects only.
(let (s) (-each-while '(2 4 5 6) 'even? (lambda (item) (push item s))) s)
⇒ '(4 2)
(let (s) (--each-while '(1 2 3 4) (< it 3) (push it s)) s)
⇒ '(2 1)
(let ((s 0)) (--each-while '(1 3 4 5) (odd? it) (setq s (+ s it))) s)
⇒ 4
-- Function: -each-indexed (list fn)
Call (FN index item) for each item in LIST.
In the anaphoric form ‘--each-indexed’, the index is exposed as
symbol ‘it-index’.
See also: ‘-map-indexed’ (*note -map-indexed::).
(let (s) (-each-indexed '(a b c) (lambda (index item) (setq s (cons (list item index) s)))) s)
⇒ '((c 2) (b 1) (a 0))
(let (s) (--each-indexed '(a b c) (setq s (cons (list it it-index) s))) s)
⇒ '((c 2) (b 1) (a 0))
-- Function: -each-r (list fn)
Call FN with every item in LIST in reversed order. Return nil,
used for side-effects only.
(let (s) (-each-r '(1 2 3) (lambda (item) (setq s (cons item s)))))
⇒ nil
(let (s) (-each-r '(1 2 3) (lambda (item) (setq s (cons item s)))) s)
⇒ '(1 2 3)
(let (s) (--each-r '(1 2 3) (setq s (cons it s))) s)
⇒ '(1 2 3)
-- Function: -each-r-while (list pred fn)
Call FN with every item in reversed LIST while (PRED item) is
non-nil. Return nil, used for side-effects only.
(let (s) (-each-r-while '(2 4 5 6) 'even? (lambda (item) (!cons item s))) s)
⇒ '(6)
(let (s) (--each-r-while '(1 2 3 4) (>= it 3) (!cons it s)) s)
⇒ '(3 4)
-- Function: -dotimes (num fn)
Repeatedly calls FN (presumably for side-effects) passing in
integers from 0 through NUM-1.
(let (s) (-dotimes 3 (lambda (n) (!cons n s))) s)
⇒ '(2 1 0)
(let (s) (--dotimes 5 (!cons it s)) s)
⇒ '(4 3 2 1 0)
-- Macro: -doto (eval-initial-value &rest forms)
Eval a form, then insert that form as the 2nd argument to other
forms. The EVAL-INITIAL-VALUE form is evaluated once. Its result
is passed to FORMS, which are then evaluated sequentially. Returns
the target form.
(-doto '(1 2 3) (!cdr) (!cdr))
⇒ '(3)
(-doto '(1 . 2) (setcar 3) (setcdr 4))
⇒ '(3 . 4)
-- Macro: --doto (eval-initial-value &rest forms)
Anaphoric form of ‘-doto’ (*note -doto::). Note: ‘it’ is not
required in each form.
(gethash "key" (--doto (make-hash-table :test 'equal) (puthash "key" "value" it)))
⇒ "value"

File: dash.info, Node: Destructive operations, Next: Function combinators, Prev: Side-effects, Up: Functions
2.15 Destructive operations
===========================
-- 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
=========================
These combinators require Emacs 24 for its lexical scope. So they are
offered in a separate package: ‘dash-functional‘.
-- Function: -partial (fn &rest args)
Take a function FN and fewer than the normal arguments to FN, and
return a fn that takes a variable number of additional ARGS. When
called, the returned function calls FN with ARGS first and then
additional args.
(funcall (-partial '- 5) 3)
⇒ 2
(funcall (-partial '+ 5 2) 3)
⇒ 10
-- Function: -rpartial (fn &rest args)
Takes a function FN and fewer than the normal arguments to FN, and
returns a fn that takes a variable number of additional ARGS. When
called, the returned function calls FN with the additional args
first and then ARGS.
(funcall (-rpartial '- 5) 8)
⇒ 3
(funcall (-rpartial '- 5 2) 10)
⇒ 3
-- Function: -juxt (&rest fns)
Takes a list of functions and returns a fn that is the
juxtaposition of those fns. The returned fn takes a variable
number of args, and returns a list containing the result of
applying each fn to the args (left-to-right).
(funcall (-juxt '+ '-) 3 5)
⇒ '(8 -2)
(-map (-juxt 'identity 'square) '(1 2 3))
⇒ '((1 1) (2 4) (3 9))
-- Function: -compose (&rest fns)
Takes a list of functions and returns a fn that is the composition
of those fns. The returned fn takes a variable number of
arguments, and returns the result of applying each fn to the result
of applying the previous fn to the arguments (right-to-left).
(funcall (-compose 'square '+) 2 3)
⇒ (square (+ 2 3))
(funcall (-compose 'identity 'square) 3)
⇒ (square 3)
(funcall (-compose 'square 'identity) 3)
⇒ (square 3)
-- Function: -applify (fn)
Changes an n-arity function FN to a 1-arity function that expects a
list with n items as arguments
(-map (-applify '+) '((1 1 1) (1 2 3) (5 5 5)))
⇒ '(3 6 15)
(-map (-applify (lambda (a b c) `(,a (,b (,c))))) '((1 1 1) (1 2 3) (5 5 5)))
⇒ '((1 (1 (1))) (1 (2 (3))) (5 (5 (5))))
(funcall (-applify '<) '(3 6))
⇒ t
-- Function: -on (operator transformer)
Return a function of two arguments that first applies TRANSFORMER
to each of them and then applies OPERATOR on the results (in the
same order).
In types: (b -> b -> c) -> (a -> b) -> a -> a -> c
(-sort (-on '< 'length) '((1 2 3) (1) (1 2)))
⇒ '((1) (1 2) (1 2 3))
(-min-by (-on '> 'length) '((1 2 3) (4) (1 2)))
⇒ '(4)
(-min-by (-on 'string-lessp 'number-to-string) '(2 100 22))
⇒ 22
-- Function: -flip (func)
Swap the order of arguments for binary function FUNC.
In types: (a -> b -> c) -> b -> a -> c
(funcall (-flip '<) 2 1)
⇒ t
(funcall (-flip '-) 3 8)
⇒ 5
(-sort (-flip '<) '(4 3 6 1))
⇒ '(6 4 3 1)
-- 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
(-map (-const 1) '("a" "b" "c" "d"))
⇒ '(1 1 1 1)
(-sum (-map (-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 'list 'vector 'string))
⇒ '((1 2 3) [1 2 3] "")
-- Function: -not (pred)
Take a unary predicate PRED and return a unary predicate that
returns t if PRED returns nil and nil if PRED returns non-nil.
(funcall (-not 'even?) 5)
⇒ t
(-filter (-not (-partial '< 4)) '(1 2 3 4 5 6 7 8))
⇒ '(1 2 3 4)
-- Function: -orfn (&rest preds)
Take list of unary predicates PREDS and return a unary predicate
with argument x that returns non-nil if at least one of the PREDS
returns non-nil on x.
In types: [a -> Bool] -> a -> Bool
(-filter (-orfn 'even? (-partial (-flip '<) 5)) '(1 2 3 4 5 6 7 8 9 10))
⇒ '(1 2 3 4 6 8 10)
(funcall (-orfn 'stringp 'even?) "foo")
⇒ t
-- Function: -andfn (&rest preds)
Take list of unary predicates PREDS and return a unary predicate
with argument x that returns non-nil if all of the PREDS returns
non-nil on x.
In types: [a -> Bool] -> a -> Bool
(funcall (-andfn (-cut < <> 10) 'even?) 6)
⇒ t
(funcall (-andfn (-cut < <> 10) 'even?) 12)
⇒ nil
(-filter (-andfn (-not 'even?) (-cut >= 5 <>)) '(1 2 3 4 5 6 7 8 9 10))
⇒ '(1 3 5)
-- 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-equal) 0.7)
⇒ 0.7390851332151607
(funcall (-fixfn (lambda (x) (expt (+ x 10) 0.25))) 2.0)
⇒ 1.8555845286409378
(funcall (-fixfn 'sin 'approx-equal) 0.1)
⇒ '(halted . t)
-- Function: -prodfn (&rest fns)
Take a list of n functions and return a function that takes a list
of length n, applying i-th function to i-th 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) (7 8)))
⇒ '((2 1) (4 3) (6 5) (8 7))
(apply '+ (funcall (-prodfn 'length 'string-to-number) '((1 2 3) "15")))
⇒ 18

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

File: dash.info, Node: Contribute, Next: Changes, Up: Development
3.1 Contribute
==============
Yes, please do. Pure functions in the list manipulation realm only,
please. There’s a suite of tests in dev/examples.el, so remember to add
tests for your function, or it might get broken later.
Run the tests with ‘./run-tests.sh’. Create the docs with
‘./create-docs.sh’. I highly recommend that you install these as a
pre-commit hook, so that the tests are always running and the docs are
always in sync:
cp pre-commit.sh .git/hooks/pre-commit
Oh, and don’t edit ‘README.md’ directly, it is auto-generated.
Change ‘readme-template.md’ or ‘examples-to-docs.el’ instead. The same
goes for the info manual.

File: dash.info, Node: Changes, Next: Contributors, Prev: Contribute, Up: Development
3.2 Changes
===========
Changes in 2.10:
• Add ‘-let’ destructuring to ‘-if-let’ and ‘-when-let’ (Fredrik
Bergroth)
Changes in 2.9:
• Add ‘-let’, ‘-let*’ and ‘-lambda’ with destructuring
• Add ‘-tree-seq’ and ‘-tree-map-nodes’
• Add ‘-non-nil’
• Add ‘-fix’
• Add ‘-fixfn’ (dash-functional 1.2)
• Add ‘-copy’ (Wilfred Hughes)
Changes in 2.8:
• Add ‘-butlast’
Changes in 2.7:
• ‘-zip’ now supports more than two lists (Steve Lamb)
• Add ‘-cycle’, ‘-pad’, ‘-annotate’, ‘-zip-fill’ (Steve Lamb)
• Add ‘-table’, ‘-table-flat’ (finite cartesian product)
• Add ‘-flatten-n’
• ‘-slice’ now supports "step" argument
• Add functional combinators ‘-iteratefn’, ‘-prodfn’
• Add ‘-replace’, ‘-splice’, ‘-splice-list’ which generalize
‘-replace-at’ and ‘-insert-at’
• Add ‘-compose’, ‘-iteratefn’ and ‘-prodfn’ (dash-functional 1.1)
Changes in 2.6:
• Add ‘-is-prefix-p’, ‘-is-suffix-p’, ‘-is-infix-p’ (Matus Goljer)
• Add ‘-iterate’, ‘-unfold’ (Matus Goljer)
• Add ‘-split-on’, ‘-split-when’ (Matus Goljer)
• Add ‘-find-last-index’ (Matus Goljer)
• Add ‘-list’ (Johan Andersson)
Changes in 2.5:
• Add ‘-same-items?’ (Johan Andersson)
• A few bugfixes
Changes in 2.4:
• Add ‘-snoc’ (Matus Goljer)
• Add ‘-replace-at’, ‘-update-at’, ‘-remove-at’, and
‘-remove-at-indices’ (Matus Goljer)
Changes in 2.3:
• Add tree operations (Matus Goljer)
• Make font-lock optional
Changes in 2.2:
• Add ‘-compose’ (Christina Whyte)
Changes in 2.1:
• Add indexing operations (Matus Goljer)
Changes in 2.0:
• Split out ‘dash-functional.el’ (Matus Goljer)
• Add ‘-andfn’, ‘-orfn’, ‘-not’, ‘-cut’, ‘-const’, ‘-flip’ and ‘-on’.
(Matus Goljer)
• Fix ‘-min’, ‘-max’, ‘-min-by’ and ‘-max-by’ (Matus Goljer)
Changes in 1.8:
• Add ‘-first-item’ and ‘-last-item’ (Wilfred Hughes)
Changes in 1.7:
• Add ‘-rotate’ (Matus Goljer)
Changes in 1.6:
• Add ‘-min’, ‘-max’, ‘-min-by’ and ‘-max-by’ (Johan Andersson)
Changes in 1.5:
• Add ‘-sum’ and ‘-product’ (Johan Andersson)
Changes in 1.4:
• Add ‘-sort’
• Add ‘-reduce-r’ (Matus Goljer)
• Add ‘-reduce-r-from’ (Matus Goljer)
Changes in 1.3:
• Add ‘-partition-in-steps’
• Add ‘-partition-all-in-steps’
Changes in 1.2:
• Add ‘-last’ (Matus Goljer)
• Add ‘-insert-at’ (Emanuel Evans)
• Add ‘-when-let’ and ‘-if-let’ (Emanuel Evans)
• Add ‘-when-let*’ and ‘-if-let*’ (Emanuel Evans)
• Some bugfixes

File: dash.info, Node: Contributors, Prev: Changes, Up: Development
3.3 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 an n-ary version of ‘-zip’.
• Fredrik Bergroth (https://github.com/fbergroth) made the ‘-if-let’
family use ‘-let’ destructuring and improved script for generating
documentation.
• Mark Oteiza (https://github.com/holomorph) contributed 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.
Thanks!

File: dash.info, Node: Index, Prev: Development, Up: Top
Index
*****
[index]
* Menu:
* !cdr: Destructive operations.
(line 14)
* !cons: Destructive operations.
(line 6)
* -->: Threading macros. (line 32)
* --doto: Side-effects. (line 83)
* ->: Threading macros. (line 6)
* ->>: Threading macros. (line 19)
* -all?: Predicates. (line 18)
* -andfn: Function combinators.
(line 138)
* -annotate: Maps. (line 79)
* -any?: Predicates. (line 6)
* -applify: Function combinators.
(line 55)
* -as->: Threading macros. (line 46)
* -butlast: Other list operations.
(line 340)
* -clone: Tree operations. (line 122)
* -common-prefix: Reductions. (line 223)
* -common-suffix: Reductions. (line 233)
* -compose: Function combinators.
(line 42)
* -concat: List to list. (line 22)
* -cons*: Other list operations.
(line 30)
* -const: Function combinators.
(line 92)
* -contains?: Predicates. (line 57)
* -copy: Maps. (line 134)
* -count: Reductions. (line 151)
* -cut: Function combinators.
(line 104)
* -cycle: Other list operations.
(line 168)
* -difference: Set operations. (line 20)
* -distinct: Set operations. (line 62)
* -dotimes: Side-effects. (line 63)
* -doto: Side-effects. (line 72)
* -drop: Sublist selection. (line 124)
* -drop-last: Sublist selection. (line 136)
* -drop-while: Sublist selection. (line 157)
* -each: Side-effects. (line 8)
* -each-indexed: Side-effects. (line 30)
* -each-r: Side-effects. (line 43)
* -each-r-while: Side-effects. (line 54)
* -each-while: Side-effects. (line 19)
* -elem-index: Indexing. (line 9)
* -elem-indices: Indexing. (line 21)
* -fifth-item: Other list operations.
(line 320)
* -filter: Sublist selection. (line 8)
* -find-index: Indexing. (line 32)
* -find-indices: Indexing. (line 60)
* -find-last-index: Indexing. (line 46)
* -first: Other list operations.
(line 234)
* -first-item: Other list operations.
(line 271)
* -fix: Other list operations.
(line 376)
* -fixfn: Function combinators.
(line 175)
* -flatten: List to list. (line 33)
* -flatten-n: List to list. (line 55)
* -flip: Function combinators.
(line 80)
* -fourth-item: Other list operations.
(line 310)
* -grade-down: Indexing. (line 81)
* -grade-up: Indexing. (line 71)
* -group-by: Partitioning. (line 187)
* -if-let: Binding. (line 36)
* -if-let*: Binding. (line 49)
* -inits: Reductions. (line 203)
* -insert-at: List to list. (line 109)
* -interleave: Other list operations.
(line 68)
* -interpose: Other list operations.
(line 58)
* -intersection: Set operations. (line 32)
* -is-infix?: Predicates. (line 110)
* -is-prefix?: Predicates. (line 86)
* -is-suffix?: Predicates. (line 98)
* -iterate: Unfolding. (line 9)
* -iteratefn: Function combinators.
(line 152)
* -juxt: Function combinators.
(line 31)
* -keep: List to list. (line 8)
* -lambda: Binding. (line 252)
* -last: Other list operations.
(line 261)
* -last-item: Other list operations.
(line 330)
* -let: Binding. (line 65)
* -let*: Binding. (line 232)
* -list: Other list operations.
(line 363)
* -map: Maps. (line 10)
* -map-first: Maps. (line 37)
* -map-indexed: Maps. (line 65)
* -map-last: Maps. (line 51)
* -map-when: Maps. (line 21)
* -mapcat: Maps. (line 123)
* -max: Reductions. (line 267)
* -max-by: Reductions. (line 277)
* -min: Reductions. (line 243)
* -min-by: Reductions. (line 253)
* -non-nil: Sublist selection. (line 79)
* -none?: Predicates. (line 30)
* -not: Function combinators.
(line 117)
* -on: Function combinators.
(line 66)
* -only-some?: Predicates. (line 42)
* -orfn: Function combinators.
(line 126)
* -pad: Other list operations.
(line 179)
* -partial: Function combinators.
(line 9)
* -partition: Partitioning. (line 74)
* -partition-after-item: Partitioning. (line 177)
* -partition-after-pred: Partitioning. (line 145)
* -partition-all: Partitioning. (line 86)
* -partition-all-in-steps: Partitioning. (line 109)
* -partition-before-item: Partitioning. (line 167)
* -partition-before-pred: Partitioning. (line 156)
* -partition-by: Partitioning. (line 121)
* -partition-by-header: Partitioning. (line 132)
* -partition-in-steps: Partitioning. (line 97)
* -permutations: Set operations. (line 52)
* -powerset: Set operations. (line 44)
* -prodfn: Function combinators.
(line 209)
* -product: Reductions. (line 181)
* -reduce: Reductions. (line 46)
* -reduce-from: Reductions. (line 8)
* -reduce-r: Reductions. (line 65)
* -reduce-r-from: Reductions. (line 27)
* -reductions: Reductions. (line 119)
* -reductions-from: Reductions. (line 87)
* -reductions-r: Reductions. (line 135)
* -reductions-r-from: Reductions. (line 103)
* -remove: Sublist selection. (line 23)
* -remove-at: List to list. (line 145)
* -remove-at-indices: List to list. (line 158)
* -remove-first: Sublist selection. (line 37)
* -remove-item: Sublist selection. (line 67)
* -remove-last: Sublist selection. (line 52)
* -repeat: Other list operations.
(line 19)
* -replace: List to list. (line 67)
* -replace-at: List to list. (line 120)
* -replace-first: List to list. (line 81)
* -replace-last: List to list. (line 95)
* -rotate: Other list operations.
(line 8)
* -rpartial: Function combinators.
(line 20)
* -running-product: Reductions. (line 191)
* -running-sum: Reductions. (line 169)
* -same-items?: Predicates. (line 72)
* -second-item: Other list operations.
(line 286)
* -select-by-indices: Sublist selection. (line 168)
* -select-column: Sublist selection. (line 198)
* -select-columns: Sublist selection. (line 179)
* -separate: Partitioning. (line 63)
* -setq: Binding. (line 274)
* -slice: Sublist selection. (line 85)
* -snoc: Other list operations.
(line 44)
* -some: Other list operations.
(line 248)
* -some-->: Threading macros. (line 83)
* -some->: Threading macros. (line 59)
* -some->>: Threading macros. (line 71)
* -sort: Other list operations.
(line 350)
* -splice: Maps. (line 90)
* -splice-list: Maps. (line 110)
* -split-at: Partitioning. (line 8)
* -split-on: Partitioning. (line 28)
* -split-when: Partitioning. (line 46)
* -split-with: Partitioning. (line 17)
* -sum: Reductions. (line 159)
* -table: Other list operations.
(line 190)
* -table-flat: Other list operations.
(line 209)
* -tails: Reductions. (line 213)
* -take: Sublist selection. (line 101)
* -take-last: Sublist selection. (line 112)
* -take-while: Sublist selection. (line 146)
* -third-item: Other list operations.
(line 298)
* -tree-map: Tree operations. (line 28)
* -tree-map-nodes: Tree operations. (line 39)
* -tree-mapreduce: Tree operations. (line 84)
* -tree-mapreduce-from: Tree operations. (line 103)
* -tree-reduce: Tree operations. (line 52)
* -tree-reduce-from: Tree operations. (line 69)
* -tree-seq: Tree operations. (line 8)
* -unfold: Unfolding. (line 25)
* -union: Set operations. (line 8)
* -unzip: Other list operations.
(line 146)
* -update-at: List to list. (line 132)
* -when-let: Binding. (line 9)
* -when-let*: Binding. (line 23)
* -zip: Other list operations.
(line 95)
* -zip-fill: Other list operations.
(line 138)
* -zip-lists: Other list operations.
(line 119)
* -zip-with: Other list operations.
(line 79)

Tag Table:
Node: Top946
Node: Installation2422
Node: Using in a package2989
Node: Fontification of special variables3350
Node: Functions4054
Node: Maps5265
Ref: -map5560
Ref: -map-when5901
Ref: -map-first6479
Ref: -map-last6957
Ref: -map-indexed7430
Ref: -annotate7910
Ref: -splice8400
Ref: -splice-list9181
Ref: -mapcat9643
Ref: -copy10019
Node: Sublist selection10223
Ref: -filter10416
Ref: -remove10868
Ref: -remove-first11274
Ref: -remove-last11801
Ref: -remove-item12322
Ref: -non-nil12717
Ref: -slice12876
Ref: -take13408
Ref: -take-last13716
Ref: -drop14039
Ref: -drop-last14312
Ref: -take-while14572
Ref: -drop-while14922
Ref: -select-by-indices15278
Ref: -select-columns15792
Ref: -select-column16498
Node: List to list16962
Ref: -keep17154
Ref: -concat17657
Ref: -flatten17954
Ref: -flatten-n18713
Ref: -replace19100
Ref: -replace-first19563
Ref: -replace-last20060
Ref: -insert-at20550
Ref: -replace-at20877
Ref: -update-at21267
Ref: -remove-at21758
Ref: -remove-at-indices22246
Node: Reductions22828
Ref: -reduce-from22997
Ref: -reduce-r-from23763
Ref: -reduce24530
Ref: -reduce-r25259
Ref: -reductions-from26130
Ref: -reductions-r-from26845
Ref: -reductions27570
Ref: -reductions-r28195
Ref: -count28830
Ref: -sum29054
Ref: -running-sum29243
Ref: -product29536
Ref: -running-product29745
Ref: -inits30058
Ref: -tails30306
Ref: -common-prefix30553
Ref: -common-suffix30850
Ref: -min31147
Ref: -min-by31373
Ref: -max31896
Ref: -max-by32121
Node: Unfolding32649
Ref: -iterate32888
Ref: -unfold33333
Node: Predicates34141
Ref: -any?34265
Ref: -all?34585
Ref: -none?34915
Ref: -only-some?35217
Ref: -contains?35702
Ref: -same-items?36091
Ref: -is-prefix?36476
Ref: -is-suffix?36799
Ref: -is-infix?37122
Node: Partitioning37476
Ref: -split-at37664
Ref: -split-with37949
Ref: -split-on38352
Ref: -split-when39028
Ref: -separate39668
Ref: -partition40110
Ref: -partition-all40562
Ref: -partition-in-steps40990
Ref: -partition-all-in-steps41487
Ref: -partition-by41972
Ref: -partition-by-header42354
Ref: -partition-after-pred42958
Ref: -partition-before-pred43302
Ref: -partition-before-item43653
Ref: -partition-after-item43964
Ref: -group-by44270
Node: Indexing44707
Ref: -elem-index44909
Ref: -elem-indices45304
Ref: -find-index45687
Ref: -find-last-index46176
Ref: -find-indices46680
Ref: -grade-up47088
Ref: -grade-down47491
Node: Set operations47901
Ref: -union48084
Ref: -difference48526
Ref: -intersection48943
Ref: -powerset49380
Ref: -permutations49593
Ref: -distinct49893
Node: Other list operations50271
Ref: -rotate50496
Ref: -repeat50866
Ref: -cons*51129
Ref: -snoc51516
Ref: -interpose51929
Ref: -interleave52227
Ref: -zip-with52596
Ref: -zip53313
Ref: -zip-lists54145
Ref: -zip-fill54846
Ref: -unzip55169
Ref: -cycle55914
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Ref: -table56639
Ref: -table-flat57428
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Ref: -fifth-item60691
Ref: -last-item60953
Ref: -butlast61245
Ref: -sort61492
Ref: -list61981
Ref: -fix62312
Node: Tree operations62852
Ref: -tree-seq63048
Ref: -tree-map63906
Ref: -tree-map-nodes64349
Ref: -tree-reduce65199
Ref: -tree-reduce-from66081
Ref: -tree-mapreduce66682
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Ref: -clone68828
Node: Threading macros69156
Ref: ->69301
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Ref: -->70297
Ref: -as->70853
Ref: -some->71308
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Ref: -some-->72118
Node: Binding72589
Ref: -when-let72801
Ref: -when-let*73286
Ref: -if-let73809
Ref: -if-let*74204
Ref: -let74821
Ref: -let*80911
Ref: -lambda81851
Ref: -setq82648
Node: Side-effects83464
Ref: -each83658
Ref: -each-while84065
Ref: -each-indexed84523
Ref: -each-r85041
Ref: -each-r-while85474
Ref: -dotimes85849
Ref: -doto86152
Ref: --doto86580
Node: Destructive operations86855
Ref: !cons87028
Ref: !cdr87234
Node: Function combinators87429
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Ref: -rpartial88097
Ref: -juxt88500
Ref: -compose88932
Ref: -applify89485
Ref: -on89916
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Node: Development96152
Node: Contribute96501
Node: Changes97249
Node: Contributors100247
Node: Index101866

End Tag Table

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