From: Bart Schaefer <schaefer@brasslantern.com>
To: Zsh hackers list <zsh-workers@zsh.org>
Subject: Re: Example / partial fix for printf with math expressions
Date: Sun, 25 Feb 2024 16:04:34 -0800 [thread overview]
Message-ID: <CAH+w=7bZBQNvft8cqQ7CahMsF9=cMGEYTbpfLOidQH=4kc5HeA@mail.gmail.com> (raw)
In-Reply-To: <20240225065400.wrb3jxr7vub6t42v@chazelas.org>
On Sat, Feb 24, 2024 at 10:54 PM Stephane Chazelas
<stephane@chazelas.org> wrote:
>
> 2024-02-24 14:40:41 +0000, Stephane Chazelas:
> [...]
> > + zlongval = (curarg) ? mathevali(metafy(curarg, curlen, META_HEAPDUP)) : 0;
>
> That incur a performance penalty:
>
> The numbers end up being metafied (earlier), unmetafied by
> printf, metafied again by printf here and that metafication
> processed by the math handler I guess.
The reason this went unobserved for so long is that metafication only
matters to a couple of things in math:
1) proper handling of parameter references, like your a[x]++ example
2) those pesky error messages that started this whole thread
As far as I can tell there are no other circumstances in which
metafication is necessary for the syntax of math expressions.
> Maybe the performance could be *improved* instead if the
> unmetafication could be skipped altogether in printf in those
> cases?
That's certainly possible, but it would mean that every branch of the
big "case" statements for %-replacement would have to do their own
unmetafy(), rather than a single loop at the top covering the entire
argv array. The -s/-S/-z options also reverse the unmetafy(), so some
heavy refactoring of bin_print() is needed to unroll this completely.
However, I think you could change META_HEAPDUP and META_USEHEAP to
META_NOALLOC, becuase you're re-metafying back into the same space
that was originally unmetafied? That might cut the performance
penalty a lot.
next prev parent reply other threads:[~2024-02-26 0:05 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-23 23:23 Bart Schaefer
2024-02-24 14:40 ` Stephane Chazelas
2024-02-24 15:10 ` Stephane Chazelas
2024-02-24 21:51 ` Bart Schaefer
2024-02-25 6:54 ` Stephane Chazelas
2024-02-26 0:04 ` Bart Schaefer [this message]
2024-02-26 17:12 ` Bart Schaefer
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAH+w=7bZBQNvft8cqQ7CahMsF9=cMGEYTbpfLOidQH=4kc5HeA@mail.gmail.com' \
--to=schaefer@brasslantern.com \
--cc=zsh-workers@zsh.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://git.vuxu.org/mirror/zsh/
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).