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Subject: |
replace-in-string: finishing touches |
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Date: |
Thu, 24 Sep 2020 22:52:06 +0200 |
The new replace-in-string function is welcome but needs a few tweaks before we
can call it done:
1. It doesn't quite work correctly with raw bytes:
(replace-in-string "\377" "x" "a\377b")
=> "axb"
(replace-in-string "\377" "x" "a\377ø")
=> "a\377ø"
The easiest solution is to reimplement it in terms of replace-regexp-in-string
for now, and optimise it later (although I feel a bit bad undoing Lars's pretty
handiwork...)
We have messy semantics here, because string-equal does not equate "\377" and
(string-to-multibyte "\377"), but string-match-p does...
2. It is documented always to return a new string, but that's a tad
over-generous nowadays; very few string functions do that. If we drop that
guarantee, we get some optimisation opportunities:
- it can return the input string itself if no matches were found (a fairly
common case)
- it can be marked pure, not just side-effect-free, so that the byte compiler
can constant-propagate through calls to it
3. The name is somewhat unfortunate since a function by that name in XEmacs
uses regexp matching.
In fact, the new function probably broke prolog-mode because of that (see
prolog-replace-in-string).
While we can fix prolog-mode, we can't easily fix code outside the Emacs tree
that may have similar problems.
Perhaps we should rename it to string-replace, in line with the modern naming
convention discussed some time ago.
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--- Begin Message ---
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Subject: |
Re: bug#43598: replace-in-string: finishing touches |
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Date: |
Sun, 27 Sep 2020 18:14:36 +0200 |
27 sep. 2020 kl. 14.02 skrev Lars Ingebrigtsen <larsi@gnus.org>:
> Please go ahead and apply.
Applied, thank you.
Looks like we are done now. string-replace seems to be substantially faster
than replace-regexp-in-string.
Good job!
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