From: Lars Ingebrigtsen <larsi@gnus.org>
Date: Sun, 11 Oct 2020 03:51:16 +0000 (+0200)
Subject: Add support for displaying short documentation for function groups
X-Git-Tag: emacs-28.0.90~5687
X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=2a7488d42d873c0ab4c24abfeb7183953cccef34;p=emacs.git

Add support for displaying short documentation for function groups

* doc/lispref/help.texi (Documentation Groups): Document it.

* lisp/help-fns.el (help-fns--mention-shortdoc-groups): Output
references to the shortdocs.

* lisp/emacs-lisp/shortdoc.el: New file.
---

diff --git a/doc/lispref/help.texi b/doc/lispref/help.texi
index d4505d5c3ff..f513a709491 100644
--- a/doc/lispref/help.texi
+++ b/doc/lispref/help.texi
@@ -37,6 +37,7 @@ Help, emacs, The GNU Emacs Manual}.
 * Describing Characters::     Making printable descriptions of
                                 non-printing characters and key sequences.
 * Help Functions::            Subroutines used by Emacs help facilities.
+* Documentation Groups::      Listing functions by groups.
 @end menu
 
 @node Documentation Basics
@@ -794,3 +795,154 @@ If this variable is non-@code{nil}, commands defined with
 echo area at first, and display the longer @var{help-text} strings only
 if the user types the help character again.
 @end defopt
+
+
+@node Documentation Groups
+@section Documentation Groups
+@cindex documentation groups
+
+Emacs can list functions based on various groupings.  For instance,
+@code{string-trim} and @code{mapconcat} are ``string'' functions, so
+@kbd{M-x shortdoc-display-group RET string RET} will give an overview
+of functions that do things with strings.
+
+The documentation groups are created with the
+@code{define-short-documentation-group} macro.  Here's a very short
+example:
+
+@lisp
+(define-short-documentation-group string
+  "Creating Strings"
+  (substring
+   :eval (substring "foobar" 0 3)
+   :eval (substring "foobar" 3))
+  (concat
+   :eval (concat "foo" "bar" "zot")))
+@end lisp
+
+The first argument is the name of the group to be defined, and then
+follows any number of function descriptions.
+
+A function can belong to any number of documentation groups.
+
+In addition to function descriptions, the list can also have string
+elements, which are used to divide a documentation group into
+sections.
+
+In each function description, the first element is the name of the
+function, and then the rest of the description is a plist, where the
+first element in each pair is a type, and the second element is a
+value.
+
+The following types are allowed:
+
+@table @code
+@item :eval
+The value should be a form that can be evaluated with no side
+effects.  The form will be used in the documentation as printed with
+@code{prin1}, except if it's a string: Then it will be inserted as is,
+and the string with then be @code{read} to return the form.  In any
+case, the form will then be evaluated, and the result used.  For
+instance:
+
+@example
+:eval (concat "foo" "bar" "zot")
+:eval "(make-string 5 ?x)"
+@end example
+
+will be printed as
+
+@example
+(concat "foo" "bar" "zot")
+=> "foobarzot"
+(make-string 5 ?x)
+=> "xxxxx"
+@end example
+
+The reason for allowing both Lisp forms and strings here is so that
+printing can be controlled in the few cases where a certain
+presentation of the form is wished for.  In the example, @samp{?x}
+would otherwise have been printed as @samp{120} if it hadn't been
+included in a string.
+
+@item :no-eval
+
+This is like @code{eval}, except that the form will not be evaluated.
+In these cases, a @code{:result} element of some kind should be
+included.
+
+@example
+:no-eval (file-symlink-p "/tmp/foo")
+:eg-result t
+@end example
+
+@item :no-eval*
+Like @code{:no-eval}, but a result of @samp{[it depends]} will always
+be inserted.
+
+@example
+:no-eval* (buffer-string)
+@end example
+
+will result in:
+
+@example
+(buffer-string)
+-> [it depends]
+@end example
+
+@item :no-value
+Like @code{:no-eval}, but is used when the function in question has no
+well-defined return value, but is used for side effect only.
+
+@item :result
+Used to output the result from non-evaluating example forms.
+
+@example
+:no-eval (setcar list 'c)
+:result c
+@end example
+
+@item :eg-result
+Used to output an example result from non-evaluating example forms.
+
+@example
+:no-eval (looking-at "f[0-9]")
+:eg-result t
+@end example
+
+@item :result-string
+@itemx :eg-result-string
+These two are the same as @code{:result} and @code{:eg-result},
+respectively, but are inserted as is.  This is useful when the result
+is unreadable or should be on a particular form:
+
+@example
+:no-eval (find-file "/tmp/foo")
+:eg-result-string "#<buffer foo>"
+:no-eval (default-file-modes)
+:eg-result-string "#o755"
+@end example
+
+@item :no-manual
+This function is not documented in the manual.
+
+@item :args
+By default, the function's actual argument list is shown.  If
+@code{:args} is present, use that instead.
+
+@example
+:args (regexp string)
+@end example
+
+@end table
+
+@defun shortdoc-add-function shortdoc-add-function group section elem
+External packages can add functions to groups with this command.  Each
+@var{elem} should be a function descriptions, as seen above.
+@var{group} is the function group, and @var{section} is what section
+in the function group to insert the function into.
+
+If @var{group} doesn't exist, it will be created.  If @var{section}
+doesn't exist, it will be added to the end of the function group.
+@end defun
diff --git a/etc/NEWS b/etc/NEWS
index e1f9382228e..3166eb22a6c 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -85,6 +85,13 @@ useful on systems such as FreeBSD which ships only with "etc/termcap".
 
 * Changes in Emacs 28.1
 
++++
+*** A new system for displaying documentation for groups of function is added.
+This can either be used by saying 'M-x short-documentation-group' and
+choosing a group, or clicking a button in the *Help* buffers when
+looking at the doc string of a function that belongs to one of these
+groups.
+
 *** New var 'redisplay-skip-initial-frame' to enable batch redisplay tests.
 Setting it to nil forces the redisplay to do its job even in the
 initial frame used in batch mode.
diff --git a/lisp/emacs-lisp/shortdoc.el b/lisp/emacs-lisp/shortdoc.el
new file mode 100644
index 00000000000..f4eeb996af9
--- /dev/null
+++ b/lisp/emacs-lisp/shortdoc.el
@@ -0,0 +1,1077 @@
+;;; shortdoc.el --- Short function summaries  -*- lexical-binding: t -*-
+
+;; Copyright (C) 2020 Free Software Foundation, Inc.
+
+;; Keywords: lisp, help
+;; Package: emacs
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs 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.
+
+;; GNU Emacs 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 GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;;; Code:
+
+(require 'macroexp)
+(require 'seq)
+(eval-when-compile (require 'cl-lib))
+
+(defgroup shortdoc nil
+  "Short documentation."
+  :group 'lisp)
+
+(defface shortdoc-section
+  '((((class color) (background dark))
+     (:inherit variable-pitch
+               :background "#303030" :extend t))
+    (((class color) (background light))
+     (:inherit variable-pitch
+               :background "#d0d0d0" :extend t)))
+  "Face used for a section.")
+
+(defface shortdoc-example
+  '((((class color) (background dark))
+     (:background "#202020" :extend t))
+    (((class color) (background light))
+     (:background "#c0c0c0" :extend t)))
+  "Face used for examples.")
+
+(defvar shortdoc--groups nil)
+
+(defmacro define-short-documentation-group (group &rest functions)
+  "Add GROUP to the list of defined documentation groups.
+FUNCTIONS is a list of elements on the form:
+
+  (fun
+   :no-manual BOOL
+   :args ARGS
+   :eval EXAMPLE-FORM
+   :no-eval EXAMPLE-FORM
+   :no-value EXAMPLE-FORM
+   :result RESULT-FORM
+   :eg-result RESULT-FORM
+   :eg-result-string RESULT-FORM)
+
+BOOL should be non-nil if the function isn't documented in the
+manual.
+
+ARGS is optional, and the functions definition is displayed
+instead in not present.
+
+If EVAL isn't a string, it will be printed with `prin1', and then
+evaled to give a result, which is also printed.  If it's a
+string, it'll be inserted as is, then the string will be `read',
+and then evaled.
+
+There can be any number of :example/:result elements."
+  `(progn
+     (setq shortdoc--groups (delq (assq ',group shortdoc--groups)
+                                  shortdoc--groups))
+     (push (cons ',group ',functions) shortdoc--groups)))
+
+(define-short-documentation-group string
+  "Making Strings"
+  (make-string
+   :args (length init)
+   :eval "(make-string 5 ?x)")
+  (string
+   :eval "(string ?a ?b ?c)")
+  (concat
+   :eval (concat "foo" "bar" "zot"))
+  (string-join
+   :no-manual t
+   :eval (string-join '("foo" "bar" "zot") " "))
+  (mapconcat
+   :eval (mapconcat (lambda (a) (concat "[" a "]"))
+                    '("foo" "bar" "zot") " "))
+  (mapcar
+   :eval (mapcar #'identity "123"))
+  (format
+   :eval (format "This number is %d" 4))
+  "Manipulating Strings"
+  (substring
+   :eval (substring "foobar" 0 3)
+   :eval (substring "foobar" 3))
+  (split-string
+   :eval (split-string "foo bar")
+   :eval (split-string "|foo|bar|" "|")
+   :eval (split-string "|foo|bar|" "|" t))
+  (string-replace
+   :eval (string-replace "foo" "bar" "foozot"))
+  (replace-regexp-in-string
+   :eval (replace-regexp-in-string "[a-z]+" "_" "*foo*"))
+  (string-trim
+   :no-manual t
+   :args (string)
+   :doc "Trim STRING of leading and trailing white space."
+   :eval (string-trim " foo "))
+  (string-trim-left
+   :no-manual t
+   :eval (string-trim-left "oofoo" "o+"))
+  (string-trim-right
+   :no-manual t
+   :eval (string-trim-right "barkss" "s+"))
+  (string-truncate-left
+   :no-manual t
+   :eval (string-truncate-left "longstring" 8))
+  (string-remove-suffix
+   :no-manual t
+   :eval (string-remove-suffix "bar" "foobar"))
+  (string-remove-prefix
+   :no-manual t
+   :eval (string-remove-prefix "foo" "foobar"))
+  (reverse
+   :eval (reverse "foo"))
+  (substring-no-properties
+   :eval (substring-no-properties (propertize "foobar" 'face 'bold) 0 3))
+  "Predicates for Strings"
+  (string-equal
+   :eval (string-equal "foo" "foo"))
+  (eq
+   :eval (eq "foo" "foo"))
+  (eql
+   :eval (eql "foo" "foo"))
+  (equal
+   :eval (equal "foo" "foo"))
+  (cl-equalp
+   :eval (cl-equalp "Foo" "foo"))
+  (stringp
+   :eval "(stringp ?a)")
+  (string-empty-p
+   :no-manual t
+   :eval (string-empty-p ""))
+  (string-blank-p
+   :no-manual t
+   :eval (string-blank-p " \n"))
+  (string-lessp
+   :eval (string-lessp "foo" "bar"))
+  (string-greaterp
+   :eval (string-greaterp "foo" "bar"))
+  (string-version-lessp
+   :eval (string-lessp "foo32.png" "bar4.png"))
+  (string-prefix-p
+   :eval (string-prefix-p "foo" "foobar"))
+  (string-suffix-p
+   :eval (string-suffix-p "bar" "foobar"))
+  "Case Manipulation"
+  (upcase
+   :eval (upcase "foo"))
+  (downcase
+   :eval (downcase "FOObar"))
+  (capitalize
+   :eval (capitalize "foo bar zot"))
+  (upcase-initials
+   :eval (upcase-initials "The CAT in the hAt"))
+  "Converting Strings"
+  (string-to-number
+   :eval (string-to-number "42")
+   :eval (string-to-number "deadbeef" 16))
+  (number-to-string
+   :eval (number-to-string 42))
+  "Data About Strings"
+  (length
+   :eval (length "foo"))
+  (string-search
+   :eval (string-search "bar" "foobarzot"))
+  (assoc-string
+   :eval (assoc-string "foo" '(("a" 1) (foo 2))))
+  (seq-position
+   :eval "(seq-position \"foobarzot\" ?z)"))
+
+(define-short-documentation-group file-name
+  "File Name Manipulation"
+  (file-name-directory
+   :eval (file-name-directory "/tmp/foo")
+   :eval (file-name-directory "/tmp/foo/"))
+  (file-name-nondirectory
+   :eval (file-name-nondirectory "/tmp/foo")
+   :eval (file-name-nondirectory "/tmp/foo/"))
+  (file-name-sans-versions
+   :args (filename)
+   :eval (file-name-sans-versions "/tmp/foo~"))
+  (file-name-extension
+   :eval (file-name-extension "/tmp/foo.txt"))
+  (file-name-sans-extension
+   :eval (file-name-sans-extension "/tmp/foo.txt"))
+  (file-name-base
+   :eval (file-name-base "/tmp/foo.txt"))
+  (file-relative-name
+   :eval (file-relative-name "/tmp/foo" "/tmp"))
+  (make-temp-name
+   :eval (make-temp-name "/tmp/foo-"))
+  (expand-file-name
+   :eval (expand-file-name "foo" "/tmp/"))
+  (substitute-in-file-name
+   :eval (substitute-in-file-name "$HOME/foo"))
+  "Directory Functions"
+  (file-name-as-directory
+   :eval (file-name-as-directory "/tmp/foo"))
+  (directory-file-name
+   :eval (directory-file-name "/tmp/foo/"))
+  (abbreviate-file-name
+   :no-eval (abbreviate-file-name "/home/some-user")
+   :eg-result "~some-user")
+  "Quoted File Names"
+  (file-name-quote
+   :args (name)
+   :eval (file-name-quote "/tmp/foo"))
+  (file-name-unquote
+   :args (name)
+   :eval (file-name-unquote "/:/tmp/foo"))
+  "Predicates"
+  (file-name-absolute-p
+   :eval (file-name-absolute-p "/tmp/foo")
+   :eval (file-name-absolute-p "foo"))
+  (directory-name-p
+   :eval (directory-name-p "/tmp/foo/"))
+  (file-name-quoted-p
+   :eval (file-name-quoted-p "/:/tmp/foo")))
+
+(define-short-documentation-group file
+  "Inserting Contents"
+  (insert-file-contents
+   :no-eval (insert-file-contents "/tmp/foo")
+   :eg-result ("/tmp/foo" 6))
+  (insert-file-contents-literally
+   :no-eval (insert-file-contents-literally "/tmp/foo")
+   :eg-result ("/tmp/foo" 6))
+  (find-file
+   :no-eval (find-file "/tmp/foo")
+   :eg-result-string "#<buffer foo>")
+  "Predicates"
+  (file-symlink-p
+   :no-eval (file-symlink-p "/tmp/foo")
+   :eg-result t)
+  (file-directory-p
+   :no-eval (file-directory-p "/tmp")
+   :eg-result t)
+  (file-regular-p
+   :no-eval (file-regular-p "/tmp/foo")
+   :eg-result t)
+  (file-exists-p
+   :no-eval (file-exists-p "/tmp/foo")
+   :eg-result t)
+  (file-readable-p
+   :no-eval (file-readable-p "/tmp/foo")
+   :eg-result t)
+  (file-writeable-p
+   :no-eval (file-writeable-p "/tmp/foo")
+   :eg-result t)
+  (file-accessible-directory-p
+   :no-eval (file-accessible-directory-p "/tmp")
+   :eg-result t)
+  (file-executable-p
+   :no-eval (file-executable-p "/bin/cat")
+   :eg-result t)
+  (file-newer-than-file-p
+   :no-eval (file-newer-than-file-p "/tmp/foo" "/tmp/bar")
+   :eg-result nil)
+  (file-equal-p
+   :no-eval (file-equal-p "/tmp/foo" "/tmp/bar")
+   :eg-result nil)
+  (file-in-directory-p
+   :no-eval (file-in-directory-p "/tmp/foo" "/tmp/")
+   :eg-result t)
+  (file-locked-p
+   :no-eval (file-locked-p "/tmp/foo")
+   :eg-result nil)
+  "Information"
+  (file-attributes
+   :no-eval* (file-attributes "/tmp"))
+  (file-truename
+   :no-eval (file-truename "/tmp/foo/bar")
+   :eg-result "/tmp/foo/zot")
+  (file-chase-links
+   :no-eval (file-chase-links "/tmp/foo/bar")
+   :eg-result "/tmp/foo/zot")
+  (vc-responsible-backend
+   :no-eval (vc-responsible-backend "/src/foo/bar.c")
+   :eg-result Git)
+  (file-acl
+   :no-eval (file-acl "/tmp/foo")
+   :eg-result "user::rw-\ngroup::r--\nother::r--\n")
+  (file-extended-attributes
+   :no-eval* (file-extended-attributes "/tmp/foo"))
+  (file-selinux-context
+   :no-eval* (file-selinux-context "/tmp/foo"))
+  (locate-file
+   :no-eval (locate-file "syslog" '("/var/log" "/usr/bin"))
+   :eg-result "/var/log/syslog")
+  (executable-find
+   :no-eval (executable-find "ls")
+   :eg-result "/usr/bin/ls")
+  "Creating"
+  (make-temp-file
+   :no-eval (make-temp-file "/tmp/foo-")
+   :eg-result "/tmp/foo-ZcXFMj")
+  (make-nearby-temp-file
+   :no-eval (make-nearby-temp-file "/tmp/foo-")
+   :eg-result "/tmp/foo-xe8iON")
+  (write-region
+   :no-value (write-region (point-min) (point-max) "/tmp/foo"))
+  "Directories"
+  (make-directory
+   :no-value (make-directory "/tmp/bar/zot/" t))
+  (directory-files
+   :no-eval (directory-files "/tmp/")
+   :eg-result ("." ".." ".ICE-unix" ".Test-unix"))
+  (directory-files-recursively
+   :no-eval (directory-files-recursively "/tmp/" "\\.png\\'")
+   :eg-result ("/tmp/foo.png" "/tmp/zot.png" "/tmp/bar/foobar.png"))
+  (directory-files-and-attributes
+   :no-eval* (directory-files-and-attributes "/tmp/foo"))
+  (file-expand-wildcards
+   :no-eval (file-expand-wildcards "/tmp/*.png")
+   :eg-result ("/tmp/foo.png" "/tmp/zot.png"))
+  (locate-dominating-file
+   :no-eval (locate-dominating-file "foo.png" "/tmp/foo/bar/zot")
+   :eg-result "/tmp/foo.png")
+  (copy-directory
+   :no-value (copy-directory "/tmp/bar/" "/tmp/barcopy"))
+  (delete-directory
+   :no-value (delete-directory "/tmp/bar/"))
+  "File Operations"
+  (rename-file
+   :no-value (rename-file "/tmp/foo" "/tmp/newname"))
+  (copy-file
+   :no-value (copy-file "/tmp/foo" "/tmp/foocopy"))
+  (delete-file
+   :no-value (delete-file "/tmp/foo"))
+  (make-empty-file
+   :no-value (make-empty-file "/tmp/foo"))
+  (make-symbolic-link
+   :no-value (make-symbolic-link "/tmp/foo" "/tmp/foosymlink"))
+  (add-name-to-file
+   :no-value (add-name-to-file "/tmp/foo" "/tmp/bar"))
+  (set-file-modes
+   :no-value "(set-file-modes \"/tmp/foo\" #o644)")
+  (set-file-times
+   :no-value (set-file-times "/tmp/foo" (current-time)))
+  "File Modes"
+  (set-default-file-modes
+   :no-value "(set-default-file-modes #o755)")
+  (default-file-modes
+    :no-eval (default-file-modes)
+    :eg-result-string "#o755")
+  (file-modes-symbolic-to-number
+   :no-eval (file-modes-symbolic-to-number "a+r")
+   :eg-result-string "#o444")
+  (file-modes-number-to-symbolic
+   :eval "(file-modes-number-to-symbolic #o444)")
+  (set-file-extended-attributes
+   :no-eval (set-file-extended-attributes
+             "/tmp/foo" '((acl . "group::rxx")))
+   :eg-result t)
+  (set-file-selinux-context
+   :no-eval (set-file-selinux-context
+             "/tmp/foo" '(unconfined_u object_r user_home_t s0))
+   :eg-result t)
+  (set-file-acl
+   :no-eval (set-file-acl "/tmp/foo" "group::rxx")
+   :eg-result t))
+
+
+(define-short-documentation-group list
+  "Making Lists"
+  (make-list
+   :eval (make-list 5 'a))
+  (cons
+   :eval (cons 1 '(2 3 4)))
+  (list
+   :eval (list 1 2 3))
+  (number-sequence
+   :eval (number-sequence 5 8))
+  "Operations on Lists"
+  (append
+   :eval (append '("foo" "bar") '("zot")))
+  (copy-tree
+   :eval (copy-tree '(1 (2 3) 4)))
+  (flatten-tree
+   :eval (flatten-tree '(1 (2 3) 4)))
+  (car
+   :eval (car '(one two three)))
+  (cdr
+   :eval (cdr '(one two three)))
+  (last
+   :eval (last '(one two three)))
+  (butlast
+   :eval (butlast '(one two three)))
+  (nbutlast
+   :eval (nbutlast (list 'one 'two 'three)))
+  (nth
+   :eval (nth 1 '(one two three)))
+  (nthcdr
+   :eval (nthcdr 1 '(one two three)))
+  (elt
+   :eval (elt '(one two three) 1))
+  (car-safe
+   :eval (car-safe '(one two three)))
+  (cdr-safe
+   :eval (cdr-safe '(one two three)))
+  (push
+   :no-eval* (push 'a list))
+  (pop
+   :no-eval* (pop list))
+  (setcar
+   :no-eval (setcar list 'c)
+   :result c)
+  (setcdr
+   :no-eval (setcdr list (list c))
+   :result '(c))
+  (nconc
+   :eval (nconc (list 1) (list 2 3 4)))
+  (delq
+   :eval (delq 2 (list 1 2 3 4))
+   :eval (delq "a" (list "a" "b" "c" "d")))
+  (delete
+   :eval (delete 2 (list 1 2 3 4))
+   :eval (delete "a" (list "a" "b" "c" "d")))
+  (remove
+   :eval (remove 2 '(1 2 3 4))
+   :eval (remove "a" '("a" "b" "c" "d")))
+  (delete-dups
+   :eval (delete-dups (list 1 2 4 3 2 4)))
+  "Mapping Over Lists"
+  (mapcar
+   :eval (mapcar #'list '(1 2 3)))
+  (mapcan
+   :eval (mapcan #'list '(1 2 3)))
+  (mapc
+   :eval (mapc #'insert '("1" "2" "3")))
+  (reduce
+   :eval (reduce #'+ '(1 2 3)))
+  (mapconcat
+   :eval (mapconcat #'identity '("foo" "bar") "|"))
+  "Predicates"
+  (listp
+   :eval (listp '(1 2 3))
+   :eval (listp nil)
+   :eval (listp '(1 . 2)))
+  (consp
+   :eval (consp '(1 2 3))
+   :eval (consp nil))
+  (proper-list-p
+   :eval (proper-list-p '(1 2 3))
+   :eval (proper-list-p nil)
+   :eval (proper-list-p '(1 . 2)))
+  (null
+   :eval (null nil))
+  (atom
+   :eval (atom 'a))
+  (nlistp
+   :eval (nlistp '(1 2 3))
+   :eval (nlistp t)
+   :eval (nlistp '(1 . 2)))
+  "Finding Elements"
+  (memq
+   :eval (memq 2 '(1 2 3))
+   :eval (memq 2.0 '(1.0 2.0 3.0))
+   :eval (memq "b" '("a" "b" "c")))
+  (member
+   :eval (member 2 '(1 2 3))
+   :eval (member "b" '("a" "b" "c")))
+  (remq
+   :eval (remq 2 '(1 2 3 2 4 2))
+   :eval (remq "b" '("a" "b" "c")))
+  (memql
+   :eval (memql 2.0 '(1.0 2.0 3.0)))
+  (member-ignore-case
+   :eval (member-ignore-case "foo" '("bar" "Foo" "zot")))
+  "Association Lists"
+  (assoc
+   :eval (assoc 'b '((a 1) (b 2))))
+  (rassoc
+   :eval (rassoc '2 '((a . 1) (b . 2))))
+  (assq
+   :eval (assq 'b '((a 1) (b 2)))
+   :eval (assq "a" '(("a" 1) ("b" 2))))
+  (rassq
+   :eval (rassq '2 '((a . 1) (b . 2))))
+  (assoc-string
+   :eval (assoc-string "foo" '(("a" 1) (foo 2))))
+  (alist-get
+   :eval (alist-get 2 '((1 . a) (2 . b))))
+  (assoc-default
+   :eval (assoc-default 2 '((1 . a) (2 . b) #'=)))
+  (copy-alist
+   :eval (copy-alist '((1 . a) (2 . b))))
+  (assq-delete-all
+   :eval (assq-delete-all 2 (list '(1 . a) '(2 . b) '(2 . c))))
+  (assoc-delete-all
+   :eval (assoc-delete-all "b" (list '("a" . a) '("b" . b) '("b" . c))))
+  "Property Lists"
+  (plist-get
+   :eval (plist-get '(a 1 b 2 c 3) 'b))
+  (plist-put
+   :no-eval (setq plist (plist-put plist 'd 4))
+   :eq-result (a 1 b 2 c 3 d 4))
+  (lax-plist-get
+   :eval (lax-plist-get '("a" 1 "b" 2 "c" 3) "b"))
+  (lax-plist-put
+   :no-eval (setq plist (plist-put plist "d" 4))
+   :eq-result '("a" 1 "b" 2 "c" 3 "d" 4))
+  (plist-member
+   :eval (plist-member '(a 1 b 2 c 3) 'b))
+  "Data About Lists"
+  (length
+   :eval (length '(a b c)))
+  (safe-length
+   :eval (safe-length '(a b c))))
+
+
+(define-short-documentation-group vector
+  (make-vector
+   :eval (make-vector 5 "foo"))
+  (vector
+   :eval (vector 1 "b" 3))
+  (vectorp
+   :eval (vectorp [1])
+   :eval (vectorp "1"))
+  (vconcat
+   :eval (vconcat '(1 2) [3 4]))
+  (append
+   :eval (append [1 2] nil))
+  (length
+   :eval (length [1 2 3]))
+  (mapcar
+   :eval (mapcar #'identity [1 2 3]))
+  (reduce
+   :eval (reduce #'+ [1 2 3]))
+  (seq-subseq
+   :eval (seq-subseq [1 2 3 4 5] 1 3)
+   :eval (seq-subseq [1 2 3 4 5] 1)))
+
+(define-short-documentation-group regexp
+  "Matching Strings"
+  (replace-regexp-in-string
+   :eval (replace-regexp-in-string "[a-z]+" "_" "*foo*"))
+  (string-match-p
+   :eval (string-match-p "^[fo]+" "foobar"))
+  (match-string
+   :eval (and (string-match "^\\([fo]+\\)b" "foobar")
+              (match-string 0 "foobar")))
+  (match-beginning
+   :no-eval (match-beginning 1)
+   :eg-result 0)
+  (match-end
+   :no-eval (match-end 1)
+   :eg-result 3)
+  "Looking in Buffers"
+  (re-search-forward
+   :no-eval (re-search-forward "^foo$" nil t)
+   :eg-result 43)
+  (re-search-backward
+   :no-eval (re-search-backward "^foo$" nil t)
+   :eg-result 43)
+  (looking-at-p
+   :no-eval (looking-at "f[0-9]")
+   :eg-result t)
+  "Utilities"
+  (regexp-quote
+   :eval (regexp-quote "foo.*bar"))
+  (regexp-opt
+   :eval (regexp-opt '("foo" "bar")))
+  (regexp-opt-depth
+   :eval (regexp-opt-depth "\\(a\\(b\\)\\)"))
+  (regexp-opt-charset
+   :eval (regexp-opt-charset '(?a ?b ?c ?d ?e))))
+
+(define-short-documentation-group sequence
+  "Sequence Predicates"
+  (seq-contains-p
+   :eval (seq-contains '(a b c) 'b)
+   :eval (seq-contains '(a b c) 'd))
+  (seq-every-p
+   :eval (seq-every-p #'numberp '(1 2 3)))
+  (seq-empty-p
+   :eval (seq-empty-p []))
+  (seq-set-equal-p
+   :eval (seq-set-equal-p '(1 2 3) '(3 1 2)))
+  (seq-some
+   :eval (seq-some #'cl-evenp '(1 2 3)))
+  "Building Sequences"
+  (seq-concatenate
+   :eval (seq-concatenate 'vector '(1 2) '(c d)))
+  (seq-copy
+   :eval (seq-copy '(a 2)))
+  (seq-into
+   :eval (seq-into '(1 2 3) 'vector))
+  "Utility Functions"
+  (seq-count
+   :eval (seq-count #'numberp '(1 b c 4)))
+  (seq-elt
+   :eval (seq-elt '(a b c) 1))
+  (seq-random-elt
+   :no-eval (seq-random-elt '(a b c))
+   :eg-result c)
+  (seq-find
+   :eval (seq-find #'numberp '(a b 3 4 f 6)))
+  (seq-position
+   :eval (seq-position '(a b c) 'c))
+  (seq-length
+   :eval (seq-length "abcde"))
+  (seq-max
+   :eval (seq-max [1 2 3]))
+  (seq-min
+   :eval (seq-min [1 2 3]))
+  (seq-first
+   :eval (seq-first [a b c]))
+  (seq-rest
+   :eval (seq-rest '[1 2 3]))
+  (seq-reverse
+   :eval (seq-reverse '(1 2 3)))
+  (seq-sort
+   :eval (seq-sort #'> '(1 2 3)))
+  (seq-sort-by
+   :eval (seq-sort-by (lambda (a) (/ 1.0 a)) #'< '(1 2 3)))
+  "Mapping Over Sequences"
+  (seq-map
+   :eval (seq-map #'1+ '(1 2 3)))
+  (seq-map-indexed
+   :eval (seq-map-indexed (lambda (a i) (cons i a)) '(a b c)))
+  (seq-mapcat
+   :eval (seq-mapcat #'upcase '("a" "b" "c") 'string))
+  (seq-do
+   :no-eval (seq-do (lambda (a) (insert a)) '("foo" "bar"))
+   :eg-result ("foo" "bar"))
+  (seq-do-indexed
+   :no-eval (seq-do-indexed
+             (lambda (a index) (message "%s:%s" index a))
+             '("foo" "bar"))
+   :eg-result nil)
+  (seq-reduce
+   :eval (seq-reduce #'* [1 2 3] 2))
+  "Excerpting Sequences"
+  (seq-drop
+   :eval (seq-drop '(a b c) 2))
+  (seq-drop-while
+   :eval (seq-drop-while #'numberp '(1 2 c d 5)))
+  (seq-filter
+   :eval (seq-filter #'numberp '(a b 3 4 f 6)))
+  (seq-remove
+   :eval (seq-remove #'numberp '(1 2 c d 5)))
+  (seq-group-by
+   :eval (seq-group-by #'cl-plusp '(-1 2 3 -4 -5 6)))
+  (seq-difference
+   :eval (seq-difference '(1 2 3) '(2 3 4)))
+  (seq-intersection
+   :eval (seq-intersection '(1 2 3) '(2 3 4)))
+  (seq-partition
+   :eval (seq-partition '(a b c d e f g h) 3))
+  (seq-subseq
+   :eval (seq-subseq '(a b c d e) 2 4))
+  (seq-take
+   :eval (seq-take '(a b c d e) 3))
+  (seq-take-while
+   :eval (seq-take-while #'cl-evenp [2 4 9 6 5]))
+  (seq-uniq
+   :eval (seq-uniq '(a b d b a c))))
+
+(define-short-documentation-group buffer
+  "Buffer Basics"
+  (current-buffer
+   :no-eval (current-buffer)
+   :eg-result-string "#<buffer shortdoc.el>")
+  (bufferp
+   :eval (bufferp 23))
+  (buffer-live-p
+   :no-eval (buffer-live-p some-buffer)
+   :eg-result t)
+  (buffer-modified-p
+   :eval (buffer-modified-p (current-buffer)))
+  (buffer-name
+   :eval (buffer-name))
+  (window-buffer
+   :eval (window-buffer))
+  "Selecting Buffers"
+  (get-buffer-create
+   :no-eval (get-buffer-create "*foo*")
+   :eg-result-string "#<buffer *foo*>")
+  (pop-to-buffer
+   :no-eval (pop-to-buffer "*foo*")
+   :eg-result-string "#<buffer *foo*>")
+  (with-current-buffer
+      :no-eval* (with-current-buffer buffer (buffer-size)))
+  "Points and Positions"
+  (point
+   :eval (point))
+  (point-min
+   :eval (point-max))
+  (point-max
+   :eval (point-max))
+  (line-beginning-position
+   :eval (line-beginning-position))
+  (line-end-position
+   :eval (line-end-position))
+  (buffer-size
+   :eval (buffer-size))
+  "Moving Around"
+  (goto-char
+   :no-eval (goto-char (point-max))
+   :eg-result 342)
+  (search-forward
+   :no-eval (search-forward "some-string" nil t)
+   :eg-result 245)
+  (re-search-forward
+   :no-eval (re-search-forward "some-s.*g" nil t)
+   :eg-result 245)
+  (forward-line
+   :no-eval (forward-line 1)
+   :eg-result 0
+   :no-eval (forward-line -2)
+   :eg-result 0)
+  "Strings from Buffers"
+  (buffer-string
+   :no-eval* (buffer-string))
+  (buffer-substring
+   :eval (buffer-substring (point-min) (+ (point-min) 10)))
+  (buffer-substring-no-properties
+   :eval (buffer-substring-no-properties (point-min) (+ (point-min) 10)))
+  (following-char
+   :no-eval (following-char)
+   :eg-result 67)
+  (char-after
+   :eval (char-after 45))
+  "Altering Buffers"
+  (delete-region
+   :no-value (delete-region (point-min) (point-max)))
+  (erase-buffer
+   :no-value (erase-buffer))
+  (insert
+   :no-value (insert "This string will be inserted in the buffer\n"))
+  "Locking"
+  (lock-buffer
+   :no-value (lock-buffer "/tmp/foo"))
+  (unlock-buffer
+   :no-value (lock-buffer)))
+
+(define-short-documentation-group process
+  (make-process
+   :no-eval (make-process :name "foo" :command '("cat" "/tmp/foo"))
+   :eg-result-string "#<process foo>")
+  (processp
+   :eval (processp t))
+  (delete-process
+   :no-value (delete-process process))
+  (kill-process
+   :no-value (kill-process process))
+  (set-process-sentinel
+   :no-value (set-process-sentinel process (lambda (proc string))))
+  (process-buffer
+   :no-eval (process-buffer process)
+   :eg-result-string "#<buffer *foo*>")
+  (get-buffer-process
+   :no-eval (get-buffer-process buffer)
+   :eg-result-string "#<process foo>")
+  (process-live-p
+   :no-eval (process-live-p process)
+   :eg-result t))
+
+(define-short-documentation-group number
+  "Arithmetic"
+  (+
+   :eval (+ 1 2)
+   :eval (+ 1 2 3 4))
+  (-
+   :eval (- 3 2)
+   :eval (- 6 3 2))
+  (*
+   :eval (* 3 4 5))
+  (/
+   :eval (/ 10 5)
+   :eval (/ 10 6)
+   :eval (/ 10.0 6)
+   :eval (/ 10.0 3 3))
+  (%
+   :eval (% 10 5)
+   :eval (% 10 6))
+  (mod
+   :eval (mod 10 5)
+   :eval (mod 10 6)
+   :eval (mod 10.5 6))
+  (1+
+   :eval (1+ 2))
+  (1-
+   :eval (1- 4))
+  "Predicates"
+  (=
+   :eval (= 4 4)
+   :eval (= 4.0 4.0)
+   :eval (= 4 5 6 7))
+  (eq
+   :eval (eq 4 4)
+   :eval (eq 4.0 4.0))
+  (eql
+   :eval (eql 4 4)
+   :eval (eql 4 "4")
+   :eval (eql 4.0 4.0))
+  (/=
+   :eval (/= 4 4))
+  (<
+   :eval (< 4 4)
+   :eval (< 1 2 3))
+  (<=
+   :eval (<= 4 4)
+   :eval (<= 1 2 3))
+  (>
+   :eval (> 4 4)
+   :eval (> 1 2 3))
+  (>=
+   :eval (>= 4 4)
+   :eval (>= 1 2 3))
+  (zerop
+   :eval (zerop 0))
+  (cl-plusp
+   :eval (cl-plusp 0)
+   :eval (cl-plusp 1))
+  (bignump
+   :eval (bignump 4)
+   :eval (bignump (expt 2 90)))
+  (fixnump
+   :eval (fixnump 4)
+   :eval (fixnump (expt 2 90)))
+  (floatp
+   :eval (floatp 5.4))
+  (integerp
+   :eval (integerp 5.4))
+  (numberp
+   :eval (numberp "5.4"))
+  (natnump
+   :eval (natnump -1)
+   :eval (natnump 23))
+  "Operations"
+  (max
+   :eval (max 7 9 3))
+  (min
+   :eval (min 7 9 3))
+  (abs
+   :eval (abs -4))
+  (float
+   :eval (float 2))
+  (truncate
+   :eval (truncate 1.2)
+   :eval (truncate -1.2)
+   :eval (truncate 5.4 2))
+  (floor
+   :eval (floor 1.2)
+   :eval (floor -1.2)
+   :eval (floor 5.4 2))
+  (ceiling
+   :eval (ceiling 1.2)
+   :eval (ceiling -1.2)
+   :eval (ceiling 5.4 2))
+  (round
+   :eval (round 1.2)
+   :eval (round -1.2)
+   :eval (round 5.4 2))
+  (random
+   :eval (random 6))
+  "Bit Operations"
+  (ash
+   :eval (ash 1 4)
+   :eval (ash 16 -1))
+  (lsh
+   :eval (lsh 1 4)
+   :eval (lsh 16 -1))
+  (logand
+   :no-eval "(logand #b10 #b111)"
+   :result-string "#b10")
+  (logior
+   :eval (logior 4 16))
+  (logxor
+   :eval (logxor 4 16))
+  (lognot
+   :eval (lognot 5))
+  (logcount
+   :eval (logcount 5))
+  "Floating Point"
+  (isnan
+   :eval (isnan 5.0))
+  (frexp
+   :eval (frexp 5.7))
+  (ldexp
+   :eval (ldexp 0.7125 3))
+  (logb
+   :eval (logb 10.5))
+  (ffloor
+   :eval (floor 1.2))
+  (fceiling
+   :eval (fceiling 1.2))
+  (ftruncate
+   :eval (ftruncate 1.2))
+  (fround
+   :eval (fround 1.2))
+  "Standard Math Functions"
+  (sin
+   :eval (sin float-pi))
+  (cos
+   :eval (cos float-pi))
+  (tan
+   :eval (tan float-pi))
+  (asin
+   :eval (asin float-pi))
+  (acos
+   :eval (acos float-pi))
+  (atan
+   :eval (atan float-pi))
+  (exp
+   :eval (exp 4))
+  (log
+   :eval (log 54.59))
+  (expt
+   :eval (expt 2 16))
+  (sqrt
+   :eval (sqrt -1)))
+
+(defun shortdoc-display-group (group)
+  "Pop to a buffer and display short documentation for functions in GROUP."
+  (interactive (list (completing-read "Show functions in: "
+                                      (mapcar #'car shortdoc--groups))))
+  (when (stringp group)
+    (setq group (intern group)))
+  (unless (assq group shortdoc--groups)
+    (error "No such documentation group %s" group))
+  (pop-to-buffer (format "*Shortdoc %s*" group))
+  (let ((inhibit-read-only t))
+    (erase-buffer)
+    (special-mode)
+    (button-mode)
+    (mapc
+     (lambda (data)
+       (cond
+        ((stringp data)
+         (insert (propertize
+                  (concat data "\n\n")
+                  'face '(variable-pitch (:height 1.3 :weight bold)))))
+        ;; There may be functions not yet defined in the data.
+        ((fboundp (car data))
+         (shortdoc--display-function data))))
+     (cdr (assq group shortdoc--groups))))
+  (goto-char (point-min)))
+
+(defun shortdoc--display-function (data)
+  (let ((function (pop data))
+        (start-section (point))
+        arglist-start)
+    ;; Function calling convention.
+    (insert "(")
+    (if (plist-get data :no-manual)
+        (insert (symbol-name function))
+      (insert-text-button
+       (symbol-name function)
+       'face 'button
+       'action (lambda (_)
+                 (info-lookup-symbol function 'emacs-lisp-mode))))
+    (setq arglist-start (point))
+    (insert ")\n")
+    ;; Doc string.
+    (insert "  "
+            (or (plist-get data :doc)
+                (car (split-string (documentation function) "\n"))))
+    (insert "\n")
+    (add-face-text-property start-section (point) 'shortdoc-section t)
+    (let ((start (point))
+          (print-escape-newlines t))
+      (cl-loop for (type value) on data by #'cddr
+               do
+               (cl-case type
+                 (:eval
+                  (if (stringp value)
+                      (insert "  " value "\n")
+                    (insert "  ")
+                    (prin1 value (current-buffer))
+                    (insert "\n")
+                    (insert "    => ")
+                    (prin1 (eval value) (current-buffer))
+                    (insert "\n")))
+                 (:no-eval*
+                  (if (stringp value)
+                      (insert "  " value "\n")
+                    (insert "  ")
+                    (prin1 value (current-buffer)))
+                  (insert "\n    -> "
+                          (propertize "[it depends]"
+                                      'face 'variable-pitch)
+                          "\n"))
+                 (:no-value
+                  (if (stringp value)
+                      (insert "  " value)
+                    (insert "  ")
+                    (prin1 value (current-buffer)))
+                  (insert "\n"))
+                 (:no-eval
+                  (if (stringp value)
+                      (insert "  " value)
+                    (insert "  ")
+                    (prin1 value (current-buffer)))
+                  (insert "\n"))
+                 (:result
+                  (insert "    => ")
+                  (prin1 value (current-buffer))
+                  (insert "\n"))
+                 (:result-string
+                  (insert "    => ")
+                  (princ value (current-buffer))
+                  (insert "\n"))
+                 (:eg-result
+                  (insert "    eg. => ")
+                  (prin1 value (current-buffer))
+                  (insert "\n"))
+                 (:eg-result-string
+                  (insert "    eg. => ")
+                  (princ value (current-buffer))
+                  (insert "\n"))))
+      (put-text-property start (point) 'face 'shortdoc-example))
+    (insert "\n")
+    ;; Insert the arglist after doing the evals, in case that's pulled
+    ;; in the function definition.
+    (save-excursion
+      (goto-char arglist-start)
+      (dolist (param (or (plist-get data :args)
+                         (help-function-arglist function t)))
+        (insert " " (symbol-name param)))
+      (add-face-text-property arglist-start (point) 'shortdoc-section t))))
+
+(defun shortdoc-function-groups (function)
+  "Return all shortdoc groups FUNCTION appears in."
+  (cl-loop for group in shortdoc--groups
+           when (assq function (cdr group))
+           collect (car group)))
+
+(defun shortdoc-add-function (group section elem)
+  "Add ELEM to shortdoc GROUP in SECTION.
+If SECTION doesn't exist, it will be added.
+
+Example:
+
+  (shortdoc-add-function
+    'file \"Predicates\"
+    '(file-locked-p :no-eval (file-locked-p \"/tmp\")))"
+  (let ((glist (assq group shortdoc--groups)))
+    (unless glist
+      (setq glist (list group))
+      (setq shortdoc--groups (append shortdoc--groups (list glist))))
+    (let ((slist (member section glist)))
+      (unless slist
+        (setq slist (list section))
+        (setq slist (append glist slist)))
+      (while (and (cdr slist)
+                  (not (stringp (cadr slist))))
+        (setq slist (cdr slist)))
+      (setcdr slist (cons elem (cdr slist))))))
+
+(provide 'shortdoc)
+
+;;; shortdoc.el ends here
diff --git a/lisp/help-fns.el b/lisp/help-fns.el
index 24fb09137c2..ee626ebc709 100644
--- a/lisp/help-fns.el
+++ b/lisp/help-fns.el
@@ -659,6 +659,39 @@ FILE is the file where FUNCTION was probably defined."
         (insert (format "  Probably introduced at or before Emacs version %s.\n"
                         first))))))
 
+(declare-function shortdoc-display-group "shortdoc")
+(declare-function shortdoc-function-groups "shortdoc")
+
+(add-hook 'help-fns-describe-function-functions
+          #'help-fns--mention-shortdoc-groups)
+(defun help-fns--mention-shortdoc-groups (object)
+  (require 'shortdoc)
+  (when-let ((groups (and (symbolp object)
+                          (shortdoc-function-groups object))))
+    (let ((start (point))
+          (times 0))
+      (with-current-buffer standard-output
+        (insert "  Other relevant functions are documented in the ")
+        (mapc
+         (lambda (group)
+           (when (> times 0)
+             (insert (if (= times (1- (length groups)))
+                         " and "
+                       ", ")))
+           (setq times (1+ times))
+           (insert-text-button
+            (symbol-name group)
+            'action (lambda (_)
+                      (shortdoc-display-group group))))
+         groups)
+        (insert (if (= (length groups) 1)
+                    " group.\n"
+                  " groups.\n")))
+      (save-restriction
+        (narrow-to-region start (point))
+        (fill-region-as-paragraph (point-min) (point-max))
+        (goto-char (point-max))))))
+
 (defun help-fns-short-filename (filename)
   (let* ((abbrev (abbreviate-file-name filename))
          (short abbrev))