diff options
| author | Lars Ingebrigtsen <larsi@gnus.org> | 2022-09-28 13:19:08 +0200 |
|---|---|---|
| committer | Lars Ingebrigtsen <larsi@gnus.org> | 2022-09-28 13:19:08 +0200 |
| commit | 12f63c18f6d5a886f62f10b4c8de8de3509e52df (patch) | |
| tree | ad7a5b8d620d976b6c9bf3c737d5bc666cbe746d /lisp/subr.el | |
| parent | fe002cc8ce38efb256a2a60660ee626c2b2cdf81 (diff) | |
| download | emacs-12f63c18f6d5a886f62f10b4c8de8de3509e52df.tar.gz emacs-12f63c18f6d5a886f62f10b4c8de8de3509e52df.tar.bz2 emacs-12f63c18f6d5a886f62f10b4c8de8de3509e52df.zip | |
Add new macro 'while-let'
* doc/lispref/control.texi (Conditionals): Document
when-let/if-let/while-let.
* lisp/subr.el (while-let): New macro.
Diffstat (limited to 'lisp/subr.el')
| -rw-r--r-- | lisp/subr.el | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/lisp/subr.el b/lisp/subr.el index 26fba4771bc..2a8fc46a9f9 100644 --- a/lisp/subr.el +++ b/lisp/subr.el @@ -2514,7 +2514,20 @@ The variable list SPEC is the same as in `if-let'." (declare (indent 1) (debug if-let)) (list 'if-let spec (macroexp-progn body))) +(defmacro while-let (spec &rest body) + "Bind variables according to SPEC and conditionally evaluate BODY. +Evaluate each binding in turn, stopping if a binding value is nil. +If all bindings are non-nil, eval BODY and repeat. +The variable list SPEC is the same as in `if-let'." + (declare (indent 1) (debug if-let)) + (let ((done (gensym "done"))) + `(catch ',done + (while t + (if-let ,spec + (progn + ,@body) + (throw ',done nil)))))) ;; PUBLIC: find if the current mode derives from another. |