Empty subexpressions captures in std.regex

[Andrei Alexandrescu]

Hi PC,


Thanks for your kind words.

Regarding regex, we need to get a report into bugzilla so we keep track 
of the problem. When you say "disable the call to optimize" are you 
referring to the -O compiler flag? In that case it's a compiler problem 
(otherwise it might be a library issue). Could you please clarify?


Thanks,

Andrei

On 07/11/2010 06:29 AM, PC wrote:
> Hi, I've been lurking in this group for a few months, have read
> through TDPL (which is great Andrei) and have started using D for
> some
> small programs. So far it's been a joy to use (you may have a C++
> convert on your hands) and with the convenience of rdmd, I've been
> using it where I'd normally use a scripting language.
>
> It's been pretty good for this especially as Phobos has had almost
> everything I've wanted to do covered. I have run into some issues
> with
> std.regex matching empty subexpressions though (dmd 2.047, win32):
>
>      auto r1 = regex( "(a*)b" );
>      auto m = match( "b", r1 );
>      writefln( "captures = %s, empty = %s", m.captures.length,
> m.empty );
>
> =>  captures = 0, empty = true
>
> If I disable the call to optimize, it gives the expected results:
>
> =>  captures = 2, empty = false
>
> Also, with optimize disabled:
>
>      auto r = regex("([^,]*),([^,]*),([^,]*)");
>      m = match( ",,", r );
>      writefln( "captures = %s, empty = %s", m.captures.length,
> m.empty );
>
> =>  captures = 3, empty = false
>
> I noticed in Captures:
>
>          @property size_t length()
>          {
>              foreach (i; 0 .. matches.length)
>              {
>                  if (matches[i].startIdx>= input.length) return i;
>              }
>              return matches.length;
>          }
>
> In this case matches[3].startIdx = 2 and matches[3].endIdx=2. Should
> this line be:
>
>       if (matches[i].startIdx>  input.length) return i;
>
>
> Anyway kudos to everyone involved with D, I'm certainly going to be
> using it a lot in the future.