Quickstart (require 'truthy) (truthy "") ; nil (truthy '[]) ; nil (truthy 0) ; nil (truthy (lambda ())) ; nil (truthy (make-sparse-keymap)) ; nil (truthy 1) ; 1 (truthy '(a b c)) ; '(a b c) (truthy '(nil nil nil)) ; nil (truthy '([] "" 0)) ; nil (truthy-s '([] "" 0)) ; '([] "" 0) ; shallow test (truthy-l '(nil nil nil)) ; '(nil nil nil) ; lengthwise test Explanation This library has no user-level interface; it is only useful for programming in Emacs Lisp. Three functions are provided: `truthy' `truthy-s' `truthy-l' Truthy provides an alternative measure of the "truthiness" of a value. Whereas Lisp considers any non-nil value to be "true" when evaluating a Boolean condition, `truthy' considers a value to be "truthy" if it has *content*. If the value is a string or buffer, it must have non-zero length. If a number, it must be non-zero. If a hash, it must have keys. If a window, it must be live. See the docstring to `truthy' for more details. `truthy' always returns its argument on success. `truthy-s' is the shallow version of `truthy'. It does not recurse into sequences, but returns success if any element of a sequence is non-nil. `truthy-l' is the "lengthwise" version of `truthy'. It does not recurse into sequences, but returns success if the argument has length, considering only the variable portion of a data type. To use truthy, place the truthy.el library somewhere Emacs can find it, and add the following to your ~/.emacs file: (require 'truthy) Notes Compatibility and Requirements GNU Emacs version 24.4-devel : yes, at the time of writing GNU Emacs version 24.3 : yes GNU Emacs version 23.3 : yes GNU Emacs version 22.3 and lower : no Uses if present: list-utils.el Bugs truthy-l is fairly meaningless on structs TODO ; License Simplified BSD License: Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. This software is provided by Roland Walker "AS IS" and any express or implied warranties, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose are disclaimed. In no event shall Roland Walker or contributors be liable for any direct, indirect, incidental, special, exemplary, or consequential damages (including, but not limited to, procurement of substitute goods or services; loss of use, data, or profits; or business interruption) however caused and on any theory of liability, whether in contract, strict liability, or tort (including negligence or otherwise) arising in any way out of the use of this software, even if advised of the possibility of such damage. The views and conclusions contained in the software and documentation are those of the authors and should not be interpreted as representing official policies, either expressed or implied, of Roland Walker.