I never said that he has to solve the halting problem.

His approach is to test against a set of input strings.°

I wouldn't be surprised if a finit input set can't cover all cases for arbitrary regexes.

This also highly depends on the allowed RegEx grammar, like embedded Perl code (at the extreme).

Cheers Rolf
(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery FootballPerl is like chess, only without the dice

°) "a few hundred sample lines"

In reply to Re^3: regex step counting (Halting problem) by LanX
in thread regex step counting by Random_Walk

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