Re^2: Greedy modifier found to be working non-greedy in a named group

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Re^3: Greedy modifier found to be working non-greedy in a named group by Corion (Patriarch) on Nov 29, 2019 at 12:13 UTC
The greedy operators still implement a leftmost-longest strategy. That means that the leftmost match will win even if you find a longer match later. `e*` can match zero e. The leftmost place where you can match zero e is at the start of the string.	[reply] [d/l]
Re^3: Greedy modifier found to be working non-greedy in a named group by hippo (Archbishop) on Nov 29, 2019 at 12:13 UTC
A greedy match is the longest representation of the first match. In the case of `/e*/` the first match is the start of the string, and is zero characters long because the first character is not an 'e'. In the case of `/e+/` the first match starts at the first 'e' and continues until it finds a non-'e' character.	[reply] [d/l] [select]
Re^3: Greedy modifier found to be working non-greedy in a named group by LanX (Saint) on Nov 29, 2019 at 12:51 UTC
> both e and e+ should have given same output. Why is the difference in output?* Good question, I think many are confused. It's important to understand that empty matches exist and that `e` means `e{0}\|e+` ( or something like `e{0,32766}` ° ). So you are actually matching `e{0}` before all! Printing out the match position of a capture group via `@+` helps demonstrating it DB<1> $_ = "This is a teeeext for testting"; DB<2> ;/(?<char>e)/ and print "'$+{char}' is matched pattern at p +os $+[0]\n"; '' is matched pattern at pos 0 DB<3> ;/(?<char>e{0})/ and print "'$+{char}' is matched pattern at + pos $+[0]\n"; '' is matched pattern at pos 0 DB<4> ;/(?<char>e+)/ and print "'$+{char}' is matched pattern at p +os $+[0]\n"; 'eeee' is matched pattern at pos 15 DB<5> ;/(?<char>e{1,32766})/ and print "'$+{char}' is matched patt +ern at pos $+[0]\n"; 'eeee' is matched pattern at pos 15 DB<6> [download] update Actually `$+[0]` gives you the end of the first match, `$-[0]` will give you the start. `e` is not limited in my Perl version but the upper bound in `e{,}` is. couldn't find positions of named groups Cheers Rolf _{(addicted to the Perl Programming Language :) Wikisyntax for the Monastery FootballPerl is like chess, only without the dice} °) yes there is an maximal upper bound in range quantifiers, which I expected to be around 2*16, so it's an incomplete analogy	[reply] [d/l] [select]
Re^4: Greedy modifier found to be working non-greedy in a named group by rsFalse (Chaplain) on Nov 30, 2019 at 15:05 UTC
> ...and that e* means e{0}\|e+ ( or something like e{0,32766} ° ). > So you are actually matching e{0} before all! And if the sentence begins with "e.."? :)	[reply]
Re^5: Greedy modifier found to be working non-greedy in a named group by LanX (Saint) on Nov 30, 2019 at 20:19 UTC
Good catch! The order must be reversed to reflect the greed. `DB<8> x 'eeeA1234eB' =~ /(e+\|e{0})(.)/ 0 'eee' 1 'A' DB<9> x 'A1234eB' =~ /(e+\|e{0})(.)/ 0 '' 1 'A' DB<10> x 'A1234eB' =~ /(e+)(.)/ 0 'e' 1 'B' DB<11>` [download] Thanks! Cheers Rolf _{(addicted to the Perl Programming Language :) Wikisyntax for the Monastery FootballPerl is like chess, only without the dice} Updates Improved demo code	[reply] [d/l]
Re^4: Greedy modifier found to be working non-greedy in a named group by rkabhi (Acolyte) on Nov 29, 2019 at 12:59 UTC
That was very good explanation. Thanks a lot !! Regards, Abhishek	[reply]
Re^3: Greedy modifier found to be working non-greedy in a named group by rkabhi (Acolyte) on Nov 29, 2019 at 12:43 UTC
Thanks, its clear now.	[reply]

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