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diff --git a/devdocs/elisp/repeated-loading.html b/devdocs/elisp/repeated-loading.html new file mode 100644 index 00000000..058db545 --- /dev/null +++ b/devdocs/elisp/repeated-loading.html @@ -0,0 +1,16 @@ + <h3 class="section">Repeated Loading</h3> <p>You can load a given file more than once in an Emacs session. For example, after you have rewritten and reinstalled a function definition by editing it in a buffer, you may wish to return to the original version; you can do this by reloading the file it came from. </p> <p>When you load or reload files, bear in mind that the <code>load</code> and <code>load-library</code> functions automatically load a byte-compiled file rather than a non-compiled file of similar name. If you rewrite a file that you intend to save and reinstall, you need to byte-compile the new version; otherwise Emacs will load the older, byte-compiled file instead of your newer, non-compiled file! If that happens, the message displayed when loading the file includes, ‘<samp>(compiled; note, source is newer)</samp>’, to remind you to recompile it. </p> <p>When writing the forms in a Lisp library file, keep in mind that the file might be loaded more than once. For example, think about whether each variable should be reinitialized when you reload the library; <code>defvar</code> does not change the value if the variable is already initialized. (See <a href="defining-variables">Defining Variables</a>.) </p> <p>The simplest way to add an element to an alist is like this: </p> <div class="example"> <pre class="example">(push '(leif-mode " Leif") minor-mode-alist) +</pre> +</div> <p>But this would add multiple elements if the library is reloaded. To avoid the problem, use <code>add-to-list</code> (see <a href="list-variables">List Variables</a>): </p> <div class="example"> <pre class="example">(add-to-list 'minor-mode-alist '(leif-mode " Leif")) +</pre> +</div> <p>Occasionally you will want to test explicitly whether a library has already been loaded. If the library uses <code>provide</code> to provide a named feature, you can use <code>featurep</code> earlier in the file to test whether the <code>provide</code> call has been executed before (see <a href="named-features">Named Features</a>). Alternatively, you could use something like this: </p> <div class="example"> <pre class="example">(defvar foo-was-loaded nil) + +(unless foo-was-loaded + <var>execute-first-time-only</var> + (setq foo-was-loaded t)) +</pre> +</div><div class="_attribution"> + <p class="_attribution-p"> + Copyright © 1990-1996, 1998-2022 Free Software Foundation, Inc. <br>Licensed under the GNU GPL license.<br> + <a href="https://www.gnu.org/software/emacs/manual/html_node/elisp/Repeated-Loading.html" class="_attribution-link">https://www.gnu.org/software/emacs/manual/html_node/elisp/Repeated-Loading.html</a> + </p> +</div> |