NEWS.md

Dash NEWS -- history of user-visible changes

Copyright (C) 2012-2026 Free Software Foundation, Inc.

See the end of the file for license conditions.

Change log

From 2.20.0 to ?.?.?

Fixes

• The -cycle function is no longer marked as pure, as it returns a copy of its argument (#405).

From 2.19.1 to 2.20.0

Deprecations

• Calling -zip with two arguments now emits a warning. This long-discouraged calling convention remains supported, but the caller is now referred to the equivalent -zip-pair instead (Stefan Monnier, #400).
• Calling -zip-pair with less than or more than two arguments is now deprecated, and can be replaced with the equivalent call to -zip-lists instead.

Fixes

• Fixed a regression from 2.18 in -take that caused it to prematurely signal an error on improper lists (#393).

• The function -pad can now be called with zero lists as arguments.

• The functions -union, -intersection, and -difference now return proper sets, without duplicate elements (#397).

• The functions -same-items? and -permutations now work on multisets (lists with duplicate elements) (#390, #397, #399).

  For example:

  (-same-items? '(1 1 2 3) '(3 1 2)) ; => t
  (-permutations '(1 1 2)) ; => '((1 1 2) (1 2 1) (2 1 1))

• Several functions which are documented as returning a fresh, mutable object (such as a copy of one of their arguments) are no longer marked as pure. Pure functions called with constant arguments are evaluated during byte-compilation; the resulting value is an immutable constant, and thus unsafe to modify destructively. The functions in question are: -clone, -cons*, -drop-last, -interleave, -interpose, -iota, -non-nil, -repeat, -slice, -snoc, -split-at, -take, -take-last (#405).

New features

• The function -contains? now returns the matching tail of the list instead of just t, similarly to member (#397).
• New function -frequencies that takes a list and counts how many times each distinct element occurs in it (suggested by @ebpa, #209, #214, #399).
• New functions -zip-lists-fill and -unzip-lists which are better-behaved versions of -zip-fill and -unzip, respectively (#400).

From 2.19.0 to 2.19.1

Fixes

• Fixed a regression from 2.18 in -is-suffix-p which led to false negatives when parts of the suffix appeared multiple times in the list being searched (Bennett Rennier, #384).

From 2.18.1 to 2.19.0

Fixes

• Reverted a breaking change introduced in 2.18.0 that caused the threading macro --> to be indented differently from -> and ->> (#375).
• Added and fixed Edebug specifications for many Dash macros (Philipp Stephani, #380, #381).

New features

• The combinators -on, -flip, -not, -andfn, and -orfn now return variadic functions that take any number of arguments (#308).
• New combinator -rotate-args similar to -flip, but for arbitrary arglist rotations (suggested by @vapniks, #72).
• New function -every and its anaphoric macro counterpart --every. They are like the existing -every-p and --every-p, respectively, but return the last non-nil result instead of just t.
• New macro --partition-after-pred which affords -partition-after-pred better performance (Per Weijnitz, #362).

From 2.18.0 to 2.18.1

• Fixed a regression from 2.17 as well as a long-standing bug in --iterate, which evaluated its arguments one too many times. This in turn could lead to errors in -flatten-n when it tried flattening certain structures too far (#373).

From 2.17 to 2.18

This release absorbs the now obsolete dash-functional version 1.3.0 into dash, and brings the very old version of dash on GNU ELPA up to date.

Package maintainers should replace all uses of dash-functional, which will eventually be deleted, with dash version 2.18.0. For more information on this, see: https://github.com/magnars/dash.el/wiki/Obsoletion-of-dash-functional.el

• New function -iota for generating arithmetic sequences (@holomorph, #215).

• Calling -list with more than one argument is now deprecated.

• -lambda now accepts an empty argument list.

• New anaphoric macros --reductions-from, --reductions, --reductions-r-from, and --reductions-r corresponding to the analogous non-anaphoric functions.

• -doto threading now works as with ->.

• New buffer-local minor mode dash-fontify-mode and globalized counterpart global-dash-fontify-mode for fontifying special Dash variables such as it, it-index, acc, etc. The minor mode also fontifies calls to Dash macros in older Emacs versions which did not dynamically detect macro calls.

  This obsoletes the user option dash-enable-fontlock and the function dash-enable-font-lock, which is now an alias of global-dash-fontify-mode.

• New command dash-register-info-lookup for integration with C-h S (info-lookup-symbol). This command allows Dash symbols to be looked up in the Dash manual just like Elisp symbols are looked up in the Elisp manual. The command can be called directly when needed, or automatically from your user-init-file. For example:

  (with-eval-after-load 'info-look
    (dash-register-info-lookup))

• Dash is now listed under the standard Customization groups and Finder keywords extensions and lisp.

• The Dash manual is now licensed under the GNU Free Documentation License version 1.3.

• Various other bug fix, performance, byte-compilation, and documentation improvements.

From 2.16 to 2.17

• Sped up -uniq by using hash-tables when possible (@cireu, #305).
• Fixed -inits to be non-destructive (@SwiftLawnGnome, #313).
• Fixed indent rules for -some-> and family (@wbolster, #321).
• Added -zip-lists which always returns a list of proper lists, even for two input lists, in contrast to -zip (see issue #135).

From 2.15 to 2.16

• Added --doto, anaphoric version of -doto (#282).
• Aliased -cons-pair-p to -cons-pair? (#288).
• Generalized -rotate for |N| greater than the length of the list (@leungbk, #290).
• Added a mechanism to extend destructuring with custom matchers (@yyoncho, #277).

From 2.14 to 2.15

This release brings new destructuring features, some new control flow functions and performance optimizations.

• Added -setq with destructuring binding support similar to the -let family (#116).
• Added smarter key destructuring in -let and friends where variables are auto-derived from keys (#111).
• Allowed -let bindings without a source value form (#256).
• Added -each-r and -each-r-while (@doublep, #159).
• Added -common-suffix (@basil-conto, #263).
• Improved performance of folds (-reduce and friends) (@basil-conto, #264).

From 2.13 to 2.14

This release retired Emacs 23 support.

• Added Edebug support for threading macros (@Wilfred).
• Added -unzip.
• Added support for -first-item and -last-item as place forms.
• Added -powerset and -permutations (@holomorph).
• Added -as-> for threading a named variable (@zck).
• Added -partition-after-pred, -partition-before-pred, -partition-after-item, and -partition-before-item (@zck).
• Fixed a bug in -any-p and friends testing for null on lists containing nil (#239).
• Fixed infinite loop bug in -zip and -interleave when called with empty input.
• Added -second-item through -fifth-item as alternatives to nth (@Wilfred).
• Added -tails and -inits.
• Added -running-sum and -running-product.
• Added the -reductions[-r][-from] family of functions (like -reduce but collecting intermediate results).
• Added -common-prefix (@basil-conto).

From 2.12 to 2.13

• -let now supports &alist destructuring.
• Various performance improvements.
• -zip might change in a future release to always return a list of proper lists. Added -zip-pair for users who explicitly want the old behavior.
• Enabled lexical binding in dash.el for Emacs versions 24 or newer (#130).
• Added -select-column and -select-columns.
• Fixed -map-last and --remove-last to be non-destructive (#158).
• Added -each-indexed and --each-indexed.
• Added -take-last and -drop-last.
• Added the -doto macro.
• -cut <> is now treated as a function, consistent with SRFI 26 (#185).

From 2.11 to 2.12

• Added GNU ELPA support (Phillip Lord).
• Added -some->, -some->>, and -some--> macros (Cam Saul).
• -is-suffix? is now non-destructive.
• Faster hash table implementation for -union.
• Improvements to docstrings and examples.

From 2.10 to 2.11

• Lots of clean up w.r.t. byte compilation, debug macros, and tests.

From 2.9 to 2.10

• Added -let destructuring to -if-let and -when-let (Fredrik Bergroth).

From 2.8 to 2.9

• Added -let, -let*, and -lambda with destructuring.
• Added -tree-seq and -tree-map-nodes.
• Added -non-nil.
• Added -fix.
• Added -fixfn (dash-functional version 1.2).
• Added -copy (Wilfred Hughes).

From 2.7 to 2.8

• Added -butlast.

From 2.6 to 2.7

• -zip now supports more than two lists (Steve Lamb).
• Added -cycle, -pad, -annotate, and -zip-fill (Steve Lamb).
• Added -table, -table-flat (finite Cartesian product).
• Added -flatten-n.
• -slice now supports a “step” argument.
• Added functional combinators -iteratefn and -prodfn.
• Added -replace, -splice, and -splice-list which generalize -replace-at and -insert-at.
• Added -compose, -iteratefn, and -prodfn (dash-functional version 1.1).

From 2.5 to 2.6

• Added -is-prefix-p, -is-suffix-p, and -is-infix-p (Matus Goljer).
• Added -iterate and -unfold (Matus Goljer).
• Added -split-on and -split-when (Matus Goljer).
• Added -find-last-index (Matus Goljer).
• Added -list (Johan Andersson).

From 2.4 to 2.5

• Added -same-items? (Johan Andersson).
• Various bugfixes.

From 2.3 to 2.4

• Added -snoc (Matus Goljer).
• Added -replace-at, -update-at, -remove-at, and -remove-at-indices (Matus Goljer).

From 2.2 to 2.3

• Added tree operations (Matus Goljer).
• Made Font Lock optional.

From 2.1 to 2.2

• Added -compose (Christina Whyte).

From 2.0 to 2.1

• Added indexing operations (Matus Goljer).

From 1.8 to 2.0

• Split out dash-functional.el (Matus Goljer).
• Added -andfn, -orfn, -not, -cut, -const, -flip, and -on (Matus Goljer).
• Fixed -min, -max, -min-by, and -max-by (Matus Goljer).

From 1.7 to 1.8

• Added -first-item and -last-item (Wilfred Hughes).

From 1.6 to 1.7

• Added -rotate (Matus Goljer).

From 1.5 to 1.6

• Added -min, -max, -min-by, and -max-by (Johan Andersson).

From 1.4 to 1.5

• Added -sum and -product (Johan Andersson).

From 1.3 to 1.4

• Added -sort.
• Added -reduce-r (Matus Goljer).
• Added -reduce-r-from (Matus Goljer).

From 1.2 to 1.3

• Added -partition-in-steps.
• Added -partition-all-in-steps.

From 1.1 to 1.2

• Added -last (Matus Goljer).
• Added -insert-at (Emanuel Evans).
• Added -when-let and -if-let (Emanuel Evans).
• Added -when-let* and -if-let* (Emanuel Evans).
• Various bugfixes.

License

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see https://www.gnu.org/licenses/.