Re: Saving match data

[Philipp Stephani <p.stephani2@gmail.com>]

[-- Attachment #1.1: Type: text/plain, Size: 553 bytes --]

Stefan Monnier <monnier@iro.umontreal.ca> schrieb am Fr., 16. Juni 2017 um
21:53 Uhr:

>
> >> Indeed, there's also an expectation that "primitives" don't touch the
> >> match-data.  It would be good to document it, tho it will take some work
> >> to clarify what is meant by "primitive".
> > At least all functions that are side-effect-free or pure (in the sense of
> > byte-opt) are trivially in this category, so we could amend the help
> texts
> > of these functions automatically.
>
> Indeed.
>
>
That's at least easy enough to do (patch attached).

[-- Attachment #1.2: Type: text/html, Size: 920 bytes --]

[-- Attachment #2: 0001-Say-that-side-effect-free-functions-don-t-change-the-m.txt --]
[-- Type: text/plain, Size: 1103 bytes --]

From 8f76c7b9e26967dad1f12636f0e7c6540c5f9ac4 Mon Sep 17 00:00:00 2001
From: Philipp Stephani <phst@google.com>
Date: Sat, 17 Jun 2017 00:13:51 +0200
Subject: [PATCH] Say that side effect-free functions don't change the matchd
 data

* lisp/help-fns.el (describe-function-1): Add note if a function is
known not to change the match data.
---
 lisp/help-fns.el | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/lisp/help-fns.el b/lisp/help-fns.el
index 2c635ffa50..54fd834839 100644
--- a/lisp/help-fns.el
+++ b/lisp/help-fns.el
@@ -699,6 +699,9 @@ describe-function-1
             (run-hook-with-args 'help-fns-describe-function-functions function)
             (insert "\n"
                     (or doc "Not documented."))
+            (when (or (function-get function 'pure)
+                      (function-get function 'side-effect-free))
+              (insert "\nThis function does not change the match data."))
             ;; Avoid asking the user annoying questions if she decides
             ;; to save the help buffer, when her locale's codeset
             ;; isn't UTF-8.
-- 
2.13.1