From 0f443a12368d02e256c7e94c3de574c6ceaed86e Mon Sep 17 00:00:00 2001 From: Nicolas Petton <nicolas@petton.fr> Date: Fri, 23 Oct 2015 13:20:45 +0200 Subject: [PATCH] New library thunk.el thunk.el is extracted from stream.el in ELPA, with additional tests. * lisp/emacs-lisp/thunk.el: New file. * test/automated/thunk-tests.el: New file. * etc/NEWS: Add information about thunk.el --- etc/NEWS | 5 +++ lisp/emacs-lisp/thunk.el | 63 +++++++++++++++++++++++++++++++++++ test/automated/thunk-tests.el | 55 ++++++++++++++++++++++++++++++ 3 files changed, 123 insertions(+) create mode 100644 lisp/emacs-lisp/thunk.el create mode 100644 test/automated/thunk-tests.el diff --git a/etc/NEWS b/etc/NEWS index 6588aad5bfc..58ab6bec161 100644 --- a/etc/NEWS +++ b/etc/NEWS @@ -582,6 +582,11 @@ prefixed with `seq-' and work on lists, strings and vectors. The map library provides map-manipulation functions that work on alists, hash-table and arrays. All functions are prefixed with "map-". +** thunk +*** New thunk library: +Thunk provides functions and macros to control the evaluation of +forms. + ** Calendar and diary +++ diff --git a/lisp/emacs-lisp/thunk.el b/lisp/emacs-lisp/thunk.el new file mode 100644 index 00000000000..ab366d295f5 --- /dev/null +++ b/lisp/emacs-lisp/thunk.el @@ -0,0 +1,63 @@ +;;; thunk.el --- Lazy form evaluation -*- lexical-binding: t -*- + +;; Copyright (C) 2015 Free Software Foundation, Inc. + +;; Author: Nicolas Petton <nicolas@petton.fr> +;; Keywords: sequences +;; Version: 1.0 +;; Package: thunk + +;; Maintainer: emacs-devel@gnu.org + +;; 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 <http://www.gnu.org/licenses/>. + +;;; Commentary: +;; +;; Thunk provides functions and macros to control the evaluation of +;; forms. Use `thunk-delay' to delay the evaluation of a form, and +;; `thunk-force' to evaluate it. Evaluation is cached, and only +;; happens once. + +;; Tests are located at test/automated/thunk-tests.el + +;;; Code: + +(defmacro thunk-delay (&rest body) + "Delay the evaluation of BODY." + (declare (debug t)) + (let ((forced (make-symbol "forced")) + (val (make-symbol "val"))) + `(let (,forced ,val) + (lambda (&optional check) + (if check + ,forced + (unless ,forced + (setf ,val (progn ,@body)) + (setf ,forced t))) + ,val)))) + +(defun thunk-force (delayed) + "Force the evaluation of DELAYED. +The result is cached and will be returned on subsequent calls +with the same DELAYED argument." + (funcall delayed)) + +(defun thunk-evaluated-p (delayed) + "Return non-nil if DELAYED has been evaluated." + (funcall delayed t)) + +(provide 'thunk) +;;; thunk.el ends here diff --git a/test/automated/thunk-tests.el b/test/automated/thunk-tests.el new file mode 100644 index 00000000000..7abbd299ead --- /dev/null +++ b/test/automated/thunk-tests.el @@ -0,0 +1,55 @@ +;;; thunk-tests.el --- Tests for thunk.el -*- lexical-binding: t -*- + +;; Copyright (C) 2015 Free Software Foundation, Inc. + +;; Author: Nicolas Petton <nicolas@petton.fr> +;; Maintainer: emacs-devel@gnu.org + +;; 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 <http://www.gnu.org/licenses/>. + +;;; Commentary: + +;; Tests for thunk.el + +;;; Code: + +(require 'ert) +(require 'thunk) + +(ert-deftest thunk-should-be-lazy () + (let (x) + (thunk-delay (setq x t)) + (should (null x)))) + +(ert-deftest thunk-can-be-evaluated () + (let* (x + (thunk (thunk-delay (setq x t)))) + (should-not (thunk-evaluated-p thunk)) + (should (null x)) + (thunk-force thunk) + (should (thunk-evaluated-p thunk)) + (should x))) + +(ert-deftest thunk-evaluation-is-cached () + (let* ((x 0) + (thunk (thunk-delay (setq x (1+ x))))) + (thunk-force thunk) + (should (= x 1)) + (thunk-force thunk) + (should (= x 1)))) + +(provide 'thunk-tests) +;;; thunk-tests.el ends here -- 2.39.5