• Markus Dangl <danglm in.tum.de> Feb 25 2007

Markus Dangl <danglm in.tum.de> writes:

Hi,
i don't know if this is really a bug, so i'm posting here in the learn 
group.
Consider the following regular expression: "^((\\w)#)?(\\w+)$"
If there is no sharp in the string to search, the whole first subpattern 
won't match, so it captures nothing (an empty string). So the subpattern 
(\\w) shouldn't capture anything, either, right?

I tested it with the following code:
------------------------------------
import std.stdio;
import std.regexp;

int main(char[][] args)
{
     auto m = std.regexp.search("test", "^((\\w)#)?(\\w+)$");
     if (m is null) { writefln("Doesn't match"); return 0; }
     for (int i=0;i<6;i++)
         writefln("%d: %s", i, m.match(i));
     return 0;
}
------------------------------------
Which displays:
0: test
1:
2: t
3: test
4:
5:

As you can see, subpattern #2 captures the first letter of the string.
I don't really know the regexp implementation, but i assume it doesn't 
throw away previously captured subpatterns after it encounters the 
mismatch with '#'.