emacs: Add "memoization" code.

* emacs/guix-utils.el (guix-memoize): New function.
  (guix-memoized-defun): New macro.
This commit is contained in:
Alex Kost 2015-06-06 22:14:13 +03:00
parent 2a4e2e4b01
commit 132e74fec9

View File

@ -1,6 +1,6 @@
;;; guix-utils.el --- General utility functions
;;; guix-utils.el --- General utility functions -*- lexical-binding: t -*-
;; Copyright © 2014 Alex Kost <alezost@gmail.com>
;; Copyright © 2014, 2015 Alex Kost <alezost@gmail.com>
;; This file is part of GNU Guix.
@ -170,6 +170,35 @@ accessed with KEYS."
"Same as `diff', but use `guix-diff-switches' as default."
(diff old new (or switches guix-diff-switches) no-async))
;;; Memoizing
(defun guix-memoize (function)
"Return a memoized version of FUNCTION."
(let ((cache (make-hash-table :test 'equal)))
(lambda (&rest args)
(let ((result (gethash args cache 'not-found)))
(if (eq result 'not-found)
(let ((result (apply function args)))
(puthash args result cache)
result)
result)))))
(defmacro guix-memoized-defun (name arglist docstring &rest body)
"Define a memoized function NAME.
See `defun' for the meaning of arguments."
(declare (doc-string 3) (indent 2))
`(defalias ',name
(guix-memoize (lambda ,arglist ,@body))
;; Add '(name args ...)' string with real arglist to the docstring,
;; because *Help* will display '(name &rest ARGS)' for a defined
;; function (since `guix-memoize' returns a lambda with '(&rest
;; args)').
,(format "(%S %s)\n\n%s"
name
(mapconcat #'symbol-name arglist " ")
docstring)))
(provide 'guix-utils)
;;; guix-utils.el ends here