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Re: regex-case
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From: |
Marko Rauhamaa |
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Subject: |
Re: regex-case |
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Date: |
Sat, 06 Feb 2016 21:49:02 +0200 |
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User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) |
Matt Wette <address@hidden>:
> Comments on syntax appreciated. — Matt
>
> === test ================
> (define str "foo")
>
> (regex-case str
> (("^([a-z]+)\\(([0-9]+)\\)$" v i)
> (list v i))
> (("^([a-z]+)$" v)
> (list v "1”)))
> =>
> (“foo” “1”)
>
>
> === syntax ==============
> (regex-case <string>
> ((<pattern> <var> <var> …) <body>)
> ((<pattern> <var> <var> …) <body>)
> (else <body>)
Seems like a great idea, especially since the compilation of the regular
expression can be done at compile-time.
Only two additions would be needed to make it better:
[1] Python's named substrings: (?P<name>...)
(<URL: https://docs.python.org/3/library/re.html?highlight=regex#reg
ular-expression-syntax>)
[2] Seamless constant string concatenation as in C:
#define PREFIX "..."
#define MIDDLE "..."
#define SUFFIX "..."
...
{
int status = regcomp(®, PREFIX MIDDLE SUFFIX, 0);
}
Now, I understand [1] is not in your hands, but named substrings are
essential in the understandability and maintainability of regular
expression code.
You might be able to do something about [2]. Without that capacity,
regular expressions might turn into kilometer-long lines or annoying
(string-concatenate) calls.
> I was thinking the above expansion has some chance (if it lives in the
> regex module?) to memoize the make-regexp part during optimization.
That would be crucial, I'm thinking.
Marko