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I noticed a pattern in some elisp modes I was putting together:

(let ((map (make-sparse-keymap)))
  (define-key map KEY 'FN)
  ...
  (setq FOO map))

so I wrote up the following macro

(defmacro def-sparse-map (name &rest key/fn-list)
  `(let ((map (make-sparse-keymap)))
     ,@(loop for (key fn) on key/fn-list by #'cddr
         collecting `(define-key map ,key ',fn))
     (setq ,name map)))

which lets me write

(def-sparse-map FOO
  KEY FN
  ...)

instead. All comments welcome, but some specific questions are

  • Can this be done more cleanly (and more generally, is it acceptable practice to use the ported CL functions when defining Elisp modes)?
  • Are there some issues I'm not seeing with that use of let/setq?
  • Is it worth it writing up an elisp with-gensyms to keep map from being bound externally?

and most importantly

  • Is there an Elisp primitive that does the same thing, or close to it?
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General notes

  • Standard modes are not supposed to use cl. This, in practice, leads to more code duplication than it saves memory (a lot of third-party modes or user init files use cl anyway). So don't worry about using it unless you're really intent on having your package integrated into GNU Emacs.
  • Yes, using the map symbol in this way will interfere a use of map outside your macro. That's what gensym is for.

My approach

You don't need a complex macro here.

(defun inaimathi-make-keymap (&rest bindings)
  "Make a sparse keymap containing the specified bindings"
  (let ((map (make-sparse-keymap)))
    (while (consp bindings)
      (define-key map (car bindings) (car (cdr bindings)))
      (setq bindings (cdr (cdr bindings))))
    map))
(defmacro inaimathi-defmap (symbol docstring &rest bindings)
  "Define a keymap called SYMBOL, with a DOCSTRING.
Populate the keymap with BINDINGS by building it with `inaimathi-make-keymap'"
  `(progn
     (defvar ,symbol nil ,docstring)
     (setq map (inaimathi-make-keymap . ,bindings))))
(inaimathi-defmap some-map "Keymap for some mode."
  "\C-c\C-a" 'do-something
  "\C-c\C-z" 'do-something-else)
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Let the macro define the keymap, whether or not you provide it the bindings at the time of creation.

(defmacro new-map (mapname &optional doc-string bindings)
  "Define keymap MAPNAME, with optional DOC-STRING and BINDINGS."
  (let ((map  (make-sparse-keymap)))
    (dolist (key.cmd  bindings)
      (define-key map (car key.cmd) (cdr key.cmd)))
    `(defvar ,mapname ',map ',doc-string)))

Use example:

(new-map my-map "My map." (("\C-cf" . forward-char)
                           ("\C-cb" . backward-char)))

Better: make adding the bindings to a map a separate function, add-bindings:

(defun add-bindings (keymap bindings)
  "Add BINDINGS to KEYMAP"
  (dolist (key.cmd  bindings)
    (define-key keymap (car key.cmd) (cdr key.cmd))))

(defmacro new-map (mapname &optional doc-string bindings)
  "Define keymap MAPNAME, with optional DOC-STRING and BINDINGS."
  (let ((map  (make-sparse-keymap)))
    (add-bindings keymap bindings)
    `(defvar ,mapname ',map ',doc-string)))

That way a program can separate creating the map from adding bindings to it (e.g., any number of times).

Use example:

(new-map my-map "My map.")                               ; Create the map
(add-bindings my-map '(("\C-cf" . forward-char)          ; Add some bindings
                       ("\C-cb" . backward-char)))
...
(add-bindings my-map '(("\C-ca" . backwardward-sentence) ; Add more bindings
                       ("\C-ce" . forward-sentence)

Define removing some bindings the same way.

(defun remove-bindings (keymap keys)
  "Remove bindings for KEYS from KEYMAP."
  (dolist (key  keys) (define-key keymap key nil)))

Use example:

(remove-bindings my-map '("\C-cb"))
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