On May 31, 6:02 am, [EMAIL PROTECTED] (Sharan Basappa) wrote: > I seem to be having some conceptual problem with greedy quantifiers .. > My understanding is that it matches as much as follows while still > allowing rest of the > regex to match.
90% correct. The other 10% is that the match starts left-to-right. It will start with the first part of the string that can match, and match as much of *that* as possible. It will not search the rest of the string to see if a longer match is possible later. For example: $string = 'abbabbbbba'; $string =~ /(b*)/; In this case, $1 will be set to 'bb', because that is the *first* longest string it could find, even though if it had continued, it would have been able to find 'bbbbb' later. > But look at the following example : > $str = mississippi; > $str =~ m/m(.*i)(.*pi)/; > print "one is $1 \n"; > print "two is $2 \n"; > > $str = mississippi; > $str =~ m/m(.*i?)(.*pi)/; This doesn't mean what you think it means. This tells Perl that the second token - (.*i?) can match as much of anything as it can, followed by 0 or 1 i's. That ? does not apply to the .* unless you put it right after the *. Compare and contrast with: (.*?i), which means to match as little of anything as possible, followed by exactly one i. > print "one is $1 \n"; > print "two is $2 \n"; > > In the first code snippet, I expected first regex (.*i) to match till > ississip Right there is a problem. Your token is (.*i). That is, the last character of this token must be an i. It can't end with a p. That doesn't match. The .* matches as much as it can until the last 'i', then saves the 'i' for the i in the token. > and leave pi for (.*pi) regex. > > But what I get as the output of this script is : > > one is ississi > two is ppi > one is ississip > two is pi > > Why is that perl is leaving ppi to second regex while it can continue > till first p It can't. The token ends in an i. 'i' must be the last thing that (.*i) matches. Paul Lalli -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/
