Re: Command Languages Versus Programming Languages

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Sujet : Re: Command Languages Versus Programming Languages
De : rweikusat (at) *nospam* talktalk.net (Rainer Weikusat)
Groupes : comp.unix.shell comp.unix.programmer comp.lang.misc
Date : 22. Nov 2024, 12:56:26
Autres entêtes
Message-ID : <87wmgvzdlh.fsf@doppelsaurus.mobileactivedefense.com>
References : 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
User-Agent : Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux)
Janis Papanagnou <janis_papanagnou+ng@hotmail.com> writes:
On 20.11.2024 18:50, Rainer Weikusat wrote:
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).
>
Okay, I see where you're coming from (and especially in that simple
case).
>
Personally (and YMMV), even here in this simple case I think that
using pointers is not better but worse - and anyway isn't [in this
form] available in most languages;

That's a question of using the proper tool for the job. In C, that's
pointer and pointer arithmetic because it's the simplest way to express
something like this.

in other cases (and languages)
such constructs get yet more clumsy, and for my not very complex
example - /[0-9]+(ABC)?x*foo/ - even a "catastrophe" concerning
readability, error-proneness, and maintainability.

Procedural code for matching strings constructed in this way is
certainly much simpler¹ than the equally procedural code for a
programmable automaton capable of interpreting regexes. Your statement
is basically "If we assume that the code interpreting regexes doesn't
exist, regexes need much less code than something equivalent which does
exist." Without this assumption, the picture becomes a different one
altogether.

¹ This doesn't even need a real state machine, just four subroutines
executed in succession (and two of these can share an implementation as
"matching ABC" and "matching foo" are both cases of matching a constant
string.

If that is what the other poster meant I'm fine with your answer;
there's no need to even consider abandoning regular expressions
in favor of explicitly codified parsing.

This depends on the specific problem and the constraints applicable to a
solution. For the common case, regexes, if easily available, are an
obvious good solution. But not all cases are common.

Date Sujet#  Auteur
29 Mar 24 * Command Languages Versus Programming Languages708Lawrence D'Oliveiro
29 Mar 24 +- Re: Command Languages Versus Programming Languages1candycanearter07
29 Mar 24 +* Re: Command Languages Versus Programming Languages19Janis Papanagnou
29 Mar 24 i+* Re: Command Languages Versus Programming Languages15Lawrence D'Oliveiro
30 Mar 24 ii`* Re: Command Languages Versus Programming Languages14Janis Papanagnou
30 Mar 24 ii +* Re: Command Languages Versus Programming Languages3Janis Papanagnou
30 Mar 24 ii i`* Re: Command Languages Versus Programming Languages2Keith Thompson
30 Mar 24 ii i `- Re: Command Languages Versus Programming Languages1Janis Papanagnou
30 Mar 24 ii +* Re: Command Languages Versus Programming Languages6Lawrence D'Oliveiro
30 Mar 24 ii i+* Re: Command Languages Versus Programming Languages3Keith Thompson
30 Mar 24 ii ii`* Re: Command Languages Versus Programming Languages2Lawrence D'Oliveiro
30 Mar 24 ii ii `- Re: Command Languages Versus Programming Languages1Keith Thompson
30 Mar 24 ii i`* Re: Command Languages Versus Programming Languages2Janis Papanagnou
30 Mar 24 ii i `- Re: Command Languages Versus Programming Languages1Lawrence D'Oliveiro
30 Mar 24 ii +* Re: Command Languages Versus Programming Languages3Keith Thompson
30 Mar 24 ii i`* Re: Command Languages Versus Programming Languages2Janis Papanagnou
30 Mar 24 ii i `- Re: Command Languages Versus Programming Languages1Keith Thompson
31 Mar 24 ii `- Re: Command Languages Versus Programming Languages1Lawrence D'Oliveiro
29 Mar 24 i`* Re: Command Languages Versus Programming Languages3Stefan Ram
30 Mar 24 i `* Re: Command Languages Versus Programming Languages2Janis Papanagnou
30 Mar 24 i  `- Re: Command Languages Versus Programming Languages1Lawrence D'Oliveiro
29 Mar 24 +* Re: Command Languages Versus Programming Languages168Muttley
29 Mar 24 i+- Re: Command Languages Versus Programming Languages1Josef Möllers
29 Mar 24 i+* Re: Command Languages Versus Programming Languages9Richard Kettlewell
29 Mar 24 ii`* Re: Command Languages Versus Programming Languages8Muttley
29 Mar 24 ii `* Re: Command Languages Versus Programming Languages7Kaz Kylheku
29 Mar 24 ii  `* Re: Command Languages Versus Programming Languages6Muttley
29 Mar 24 ii   `* Re: Command Languages Versus Programming Languages5Kaz Kylheku
30 Mar 24 ii    `* Re: Command Languages Versus Programming Languages4Muttley
30 Mar 24 ii     +- Re: Command Languages Versus Programming Languages1Janis Papanagnou
30 Mar 24 ii     `* Re: Command Languages Versus Programming Languages2Kaz Kylheku
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29 Mar 24 i`* Re: Command Languages Versus Programming Languages157John Ames
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29 Mar 24 i i+- Re: Command Languages Versus Programming Languages1John Ames
29 Mar 24 i i+* Re: Command Languages Versus Programming Languages149Kaz Kylheku
29 Mar 24 i ii`* Re: Command Languages Versus Programming Languages148Muttley
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30 Mar 24 i ii i `* Re: Command Languages Versus Programming Languages140Kaz Kylheku
1 Apr 24 i ii i  `* Re: Command Languages Versus Programming Languages139Muttley
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1 Apr 24 i ii i   i`* Re: Command Languages Versus Programming Languages136Muttley
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