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From: Rainer Weikusat <rweikusat@talktalk.net>
Newsgroups: comp.unix.shell,comp.unix.programmer,comp.lang.misc
Subject: Re: Command Languages Versus Programming Languages
Date: Wed, 20 Nov 2024 17:50:13 +0000
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Janis Papanagnou <janis_papanagnou+ng@hotmail.com> writes:

[...]

> Personally I think that writing bulky procedural stuff for something
> like [0-9]+ can only be much worse, and that further abbreviations
> like \d+ are the better direction to go if targeting a good interface.
> YMMV.

Assuming that p is a pointer to the current position in a string, e is a
pointer to the end of it (ie, point just past the last byte) and -
that's important - both are pointers to unsigned quantities, the 'bulky'
C equivalent of [0-9]+ is

while (p < e && *p - '0' < 10) ++p;

That's not too bad. And it's really a hell lot faster than a
general-purpose automaton programmed to recognize the same pattern
(which might not matter most of the time, but sometimes, it does).