Groups > comp.compilers > #1984

Re: Regular expression string searching & matching

From	Clint O <clint.olsen@gmail.com>
Newsgroups	comp.compilers
Subject	Re: Regular expression string searching & matching
Date	2018-03-08 22:53 -0800
Organization	Compilers Central
Message-ID	<18-03-034@comp.compilers> (permalink)
References	<18-03-016@comp.compilers> <18-03-032@comp.compilers>

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Hi Ben:

Thanks for your post. I did try your regular expression (and a few small
variations on it), but it exhibits the same behavior as the others I have
tried.

The difference with the complement version is that the accepting state I end
up with has all transitions to the error state (which guarantees termination
after match) where as these seem to still accept characters even after
matching the closing '*/'. It's possible I have a bug in my implementation, so
I'm still looking at it.

Thanks,

-Clint

On Wednesday, March 7, 2018 at 11:59:10 AM UTC-8, Ben Hanson wrote:
> [/][*]([^*]|[*]+[^*/])*[*]+[/]
>
> is what you are looking for. I ran into this when developing my lexer
> generator library lexertl in C++. Having a debug::dump() function
> really helped me grok what was going on.
>
> The trick of course is realising that you have to exclude the
> characters that follow (i.e. the [^*/] part). That is the bit that
> clobbers the greedy behaviour. I've had to remind myself of that on
> more than one occasion recently!

[This should work, it's a standard example in compiler texts. -John]

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Thread

Regular expression string searching & matching Clint O <clint.olsen@gmail.com> - 2018-03-04 01:37 -0800
  Re: Regular expression string searching & matching Ben Hanson <jamin.hanson@googlemail.com> - 2018-03-07 11:53 -0800
    Re: Regular expression string searching & matching Ben Hanson <jamin.hanson@googlemail.com> - 2018-03-07 12:18 -0800
    Re: Regular expression string searching & matching Clint O <clint.olsen@gmail.com> - 2018-03-08 22:53 -0800
      Re: Regular expression string searching & matching Clint O <clint.olsen@gmail.com> - 2018-03-10 00:57 -0800
        Re: Regular expression string searching & matching Ben Hanson <jamin.hanson@googlemail.com> - 2018-03-11 13:52 -0700
          Re: Regular expression string searching & matching Clint O <clint.olsen@gmail.com> - 2018-03-12 14:00 -0700
            Re: Regular expression string searching & matching Ben Hanson <jamin.hanson@googlemail.com> - 2018-03-13 11:30 -0700
              Re: Regular expression string searching & matching Clint O <clint.olsen@gmail.com> - 2018-03-17 16:52 -0700
              Re: Regular expression string searching & matching Clint O <clint.olsen@gmail.com> - 2018-03-18 19:23 +0000
              Re: Regular expression string searching & matching Clint O <clint.olsen@gmail.com> - 2018-03-20 17:23 +0000
                Re: Regular expression string searching & matching Clint O <clint.olsen@gmail.com> - 2018-03-22 17:46 +0000
          Re: Regular expression string searching & matching Ben Hanson <jamin.hanson@googlemail.com> - 2018-03-12 15:46 -0700
          Re: Regular expression string searching & matching Hans-Peter Diettrich <DrDiettrich1@netscape.net> - 2018-03-13 10:53 +0100
            Re: Regular expression string searching & matching Ben Hanson <jamin.hanson@googlemail.com> - 2018-03-13 14:23 -0700
      Re: Regular expression string searching & matching Ben Hanson <jamin.hanson@googlemail.com> - 2018-03-10 03:17 -0800

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