On Mon, 16 Jul 2001, Francois Pottier wrote:
> I have experimented a bit with custom syntax for regular expression
> matching. My goal was to implement some high-level constructs on top
> of a low-level regexp library such as PCRE. The result of my (modest)
> experiment is attached. It is a camlp4 grammar extension, which allows
> writing

Nice! This example could surely be used to build a convenient special
purpose language for text manipulation.

>   extract x, y, ... matching e against r in e'
> 
> The semantics is as follows. The expression e is evaluated, yielding
> a string which is matched against the regular expression r. r must be
> either a constant string, or a compiled regular expression; if the
> former, pre-compilation code is inserted transparently.

Note that it should be possible to assert the required number of subgroups
at compile-time if the user supplied a constant string: you'd only have
to compile the pattern string to a regexp within the camlp4-rule and
check things there. This would even allow you to catch illegal patterns:
static typing for regular expression :-)

Best regards,
Markus Mottl

-- 
Markus Mottl                                             markus@oefai.at
Austrian Research Institute
for Artificial Intelligence                  http://www.oefai.at/~markus
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