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Re: Regex refresher

by PodMaster (Abbot)
on Sep 12, 2002 at 14:30 UTC ( #197231=note: print w/replies, xml ) Need Help??


in reply to Regex refresher

When in pause, it means you don't quite understand what the pattern is saying, so it's best to get it explained
#!/usr/bin/perl -l my @L = ( "", qw{ 0 00 11 000 011 110 0000 0011 0110 1001 1100 1111 }) +; print scalar @L, " with anchors"; for(0..$#L){ print "$_)'$L[$_]'" if $L[$_] =~ /^(0|1(01*0)*1)*$/; } __END__ use YAPE::Regex::Explain; die YAPE::Regex::Explain->new(qr/(0|1(01*0)*1)*/)->explain; __DATA__ The regular expression: (?-imsx:(0|1(01*0)*1)*) matches as follows: NODE EXPLANATION ---------------------------------------------------------------------- (?-imsx: group, but do not capture (case-sensitive) (with ^ and $ matching normally) (with . not matching \n) (matching whitespace and # normally): ---------------------------------------------------------------------- ( group and capture to \1 (0 or more times (matching the most amount possible)): ---------------------------------------------------------------------- 0 '0' ---------------------------------------------------------------------- | OR ---------------------------------------------------------------------- 1 '1' ---------------------------------------------------------------------- ( group and capture to \2 (0 or more times (matching the most amount possible)): ---------------------------------------------------------------------- 0 '0' ---------------------------------------------------------------------- 1* '1' (0 or more times (matching the most amount possible)) ---------------------------------------------------------------------- 0 '0' ---------------------------------------------------------------------- )* end of \2 (NOTE: because you're using a quantifier on this capture, only the LAST repetition of the captured pattern will be stored in \2) ---------------------------------------------------------------------- 1 '1' ---------------------------------------------------------------------- )* end of \1 (NOTE: because you're using a quantifier on this capture, only the LAST repetition of the captured pattern will be stored in \1) ---------------------------------------------------------------------- ) end of grouping ----------------------------------------------------------------------
As for patterns, well, look at the regex ;D

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