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From: Marko Rauhamaa <marko@pacujo.net>
To: Matt Wette <matthew.wette@verizon.net>
Cc: guile-user@gnu.org
Subject: Re: regex-case
Date: Sat, 06 Feb 2016 21:49:02 +0200	[thread overview]
Message-ID: <87a8ndsjpt.fsf@elektro.pacujo.net> (raw)
In-Reply-To: <61E420AD-70B6-4DEA-A7DD-EB123E22EFD0@verizon.net> (Matt Wette's message of "Sat, 06 Feb 2016 11:13:25 -0800")

Matt Wette <matthew.wette@verizon.net>:

> 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(&reg, 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



  parent reply	other threads:[~2016-02-06 19:49 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-02-06 19:13 regex-case Matt Wette
2016-02-06 19:23 ` regex-case Matt Wette
2016-02-06 19:49 ` Marko Rauhamaa [this message]
2016-02-06 22:42   ` regex-case Matt Wette
2016-02-07  8:15     ` regex-case Marko Rauhamaa
2016-02-06 22:10 ` regex-case Matt Wette
2016-02-08 14:29 ` regex-case Ludovic Courtès
2016-02-11  1:19 ` regex-case Matt Wette

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