\input texinfo    @c -*- texinfo -*-
@c %**start of header
@setfilename dash.info
@set DASHVER @c [[ dash-version ]]
@settitle Dash: A modern list library for GNU Emacs.
@documentencoding UTF-8
@documentlanguage en
@c %**end of header

@copying
This manual is for Dash version @value{DASHVER}.

Copyright @copyright{} 2012--2025 Free Software Foundation, Inc.

@quotation
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with the
Invariant Sections being ``GNU General Public License,'' and no
Front-Cover Texts or Back-Cover Texts.  A copy of the license is
included in the section entitled ``GNU Free Documentation License''.
@end quotation
@end copying

@dircategory Emacs
@direntry
* Dash: (dash.info).    A modern list library for GNU Emacs.
@end direntry

@titlepage
@title Dash Manual
@subtitle For Dash Version @value{DASHVER}.
@author Magnar Sveen
@page
@vskip 0pt plus 1filll
@insertcopying
@end titlepage

@contents

@ifnottex
@node Top
@top Dash

@insertcopying
@end ifnottex

@menu
* Installation::        Installing and configuring Dash.
* Functions::           Dash API reference.
* Development::         Contributing to Dash development.

Appendices

* FDL::                 The license for this documentation.
* GPL::                 Conditions for copying and changing Dash.
* Index::               Index including functions and macros.

@detailmenu
 --- The Detailed Node Listing ---

Installation

* Using in a package::  Listing Dash as a package dependency.
* Fontification of special variables::  Font Lock of anaphoric macro variables.
* Info symbol lookup::  Looking up Dash symbols in this manual.

Functions

@c [[ function-list ]]

Development

* Contribute::          How to contribute.
* Contributors::        List of contributors.
@end detailmenu
@end menu

@node Installation
@chapter Installation

Dash is available on @url{https://elpa.gnu.org/, GNU ELPA},
@url{https://elpa.gnu.org/devel/, GNU-devel ELPA}, and
@url{https://melpa.org/, MELPA}, and can be installed with the
standard command @code{package-install} (@pxref{Package
Installation,,, emacs, The GNU Emacs Manual}).

@table @kbd
@item M-x package-install @key{RET} dash @key{RET}
Install the Dash library.
@end table

Alternatively, you can just dump @file{dash.el} in your
@code{load-path} somewhere (@pxref{Lisp Libraries,,, emacs, The GNU
Emacs Manual}).

@menu
* Using in a package::  Listing Dash as a package dependency.
* Fontification of special variables::  Font Lock of anaphoric macro variables.
* Info symbol lookup::  Looking up Dash symbols in this manual.
@end menu

@node Using in a package
@section Using in a package

If you use Dash in your own package, be sure to list it as a
dependency in the library's headers as follows (@pxref{Library
Headers,,, elisp, The Emacs Lisp Reference Manual}).

@lisp
;; Package-Requires: ((dash "@value{DASHVER}"))
@end lisp

@node Fontification of special variables
@section Fontification of special variables

@findex dash-fontify-mode
The autoloaded minor mode @code{dash-fontify-mode} is provided for
optional fontification of anaphoric Dash variables (@code{it},
@code{acc}, etc.@:) in Emacs Lisp buffers using search-based Font Lock
(@pxref{Font Lock,,, emacs, The GNU Emacs Manual}).  In older Emacs
versions which do not dynamically detect macros, the minor mode also
fontifies calls to Dash macros.

@findex global-dash-fontify-mode
To automatically enable the minor mode in all Emacs Lisp buffers, just
call its autoloaded global counterpart
@code{global-dash-fontify-mode}, either interactively or from your
@code{user-init-file}:

@lisp
(global-dash-fontify-mode)
@end lisp

@node Info symbol lookup
@section Info symbol lookup

@findex dash-register-info-lookup
While editing Elisp files, you can use @kbd{C-h S}
(@code{info-lookup-symbol}) to look up Elisp symbols in the relevant
Info manuals (@pxref{Info Lookup,,, emacs, The GNU Emacs Manual}).  To
enable the same for Dash symbols, use the command
@code{dash-register-info-lookup}.  It can be called directly when
needed, or automatically from your @code{user-init-file}.  For
example:

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

@node Functions
@chapter Functions

This chapter contains reference documentation for the Dash
@acronym{API, Application Programming Interface}.  The names of all
public functions defined in the library are prefixed with a dash
character (@samp{-}).

The library also provides anaphoric macro versions of functions where
that makes sense.  The names of these macros are prefixed with two
dashes (@samp{--}) instead of one.

For instance, while the function @code{-map} applies a function to
each element of a list, its anaphoric counterpart @code{--map}
evaluates a form with the local variable @code{it} temporarily bound
to the current list element instead.

@lisp
@group
;; Normal version.
(-map (lambda (n) (* n n)) '(1 2 3 4))
    @result{} (1 4 9 16)
@end group

@group
;; Anaphoric version.
(--map (* it it) '(1 2 3 4))
    @result{} (1 4 9 16)
@end group
@end lisp

The normal version can, of course, also be written as in the following
example, which demonstrates the utility of both versions.

@lisp
@group
(defun my-square (n)
  "Return N multiplied by itself."
  (* n n))

(-map #'my-square '(1 2 3 4))
    @result{} (1 4 9 16)
@end group
@end lisp

@menu
@c [[ function-list ]]
@end menu

@c [[ function-docs ]]
@node Development
@chapter Development

The Dash repository is hosted on GitHub at
@url{https://github.com/magnars/dash.el}.

@menu
* Contribute::          How to contribute.
* Contributors::        List of contributors.
@end menu

@node Contribute
@section Contribute

Yes, please do.  Pure functions in the list manipulation realm only,
please.  There's a suite of examples/tests in @file{dev/examples.el},
so remember to add tests for your additions, or they may get broken
later.

Run the tests with @samp{make check}.  Regenerate the docs with
@samp{make docs}.  Contributors are encouraged to install these
commands as a Git pre-commit hook, so that the tests are always
running and the docs are always in sync:

@example
$ cp dev/pre-commit.sh .git/hooks/pre-commit
@end example

Oh, and don't edit @file{README.md} or @file{dash.texi} directly, as
they are auto-generated.  Instead, change their respective templates
@file{readme-template.md} or @file{dash-template.texi}.

To ensure that Dash can be distributed with GNU ELPA or Emacs, we
require that all contributors assign copyright to the Free Software
Foundation.  For more on this, @pxref{Copyright Assignment,,, emacs,
The GNU Emacs Manual}.

@node Contributors
@section Contributors

@itemize
@item
@url{https://github.com/Fuco1, Matus Goljer} contributed lots of
features and functions.
@item
@url{https://github.com/tkf, Takafumi Arakaki} contributed
@code{-group-by}.
@item
@url{https://github.com/tali713, tali713} is the author of
@code{-applify}.
@item
@url{https://github.com/vemv, V@'{i}ctor M. Valenzuela} contributed
@code{-repeat}.
@item
@url{https://github.com/nicferrier, Nic Ferrier} contributed
@code{-cons*}.
@item
@url{https://github.com/Wilfred, Wilfred Hughes} contributed
@code{-slice}, @code{-first-item}, and @code{-last-item}.
@item
@url{https://github.com/shosti, Emanuel Evans} contributed
@code{-if-let}, @code{-when-let}, and @code{-insert-at}.
@item
@url{https://github.com/rejeep, Johan Andersson} contributed
@code{-sum}, @code{-product}, and @code{-same-items?}.
@item
@url{https://github.com/kurisuwhyte, Christina Whyte} contributed
@code{-compose}.
@item
@url{https://github.com/steventlamb, Steve Lamb} contributed
@code{-cycle}, @code{-pad}, @code{-annotate}, @code{-zip-fill}, and a
variadic version of @code{-zip}.
@item
@url{https://github.com/fbergroth, Fredrik Bergroth} made the
@code{-if-let} family use @code{-let} destructuring and improved the
script for generating documentation.
@item
@url{https://github.com/holomorph, Mark Oteiza} contributed
@code{-iota} and the script to create an Info manual.
@item
@url{https://github.com/wasamasa, Vasilij Schneidermann} contributed
@code{-some}.
@item
@url{https://github.com/occidens, William West} made @code{-fixfn}
more robust at handling floats.
@item
@url{https://github.com/camsaul, Cam Saul} contributed @code{-some->},
@code{-some->>}, and @code{-some-->}.
@item
@url{https://github.com/basil-conto, Basil L. Contovounesios}
contributed @code{-common-prefix}, @code{-common-suffix}, and various
other improvements.
@item
@url{https://github.com/doublep, Paul Pogonyshev} contributed
@code{-each-r} and @code{-each-r-while}.
@end itemize

Thanks!

New contributors are very welcome.  @xref{Contribute}.

@c Appendices.

@node FDL
@appendix GNU Free Documentation License
@include doc/fdl.texi

@node GPL
@appendix GNU General Public License
@include doc/gpl.texi

@node Index
@unnumbered Index
@printindex fn

@bye