Re: Regex Optional capture doesn't

[LanX]

I think .+ is greedy and eats the rest of the string.

But the regex is forced to backtrack if <(\w+TagIwant\b) is not optional otherwise it concludes happily.

Changing to .+? should solve this.

UPDATE

just tested, not my day. declaring myself officially (mentally) ill.

UPDATE

an elegant solution is buried at the end of this discussion here

[NetWallah]

It does not.

Same result with ".+?".

[LanX]

Yep, just tested.

But I think the explanation is still the same. (point 1)

The fix doesn't work because the regex has to decide which non-greedy ? has "precedence".

I know there are ways to handles this in one regex, but my advice is just to use a second one checking the tail of the string. (point 2)

[LanX]

Hmmm

> The fix doesn't work because the regex has to decide which non-greedy ? has "precedence".

strange, it works like I initially thought

  DB<63> print join "|",'abc' =~ /a(.+?)(c)?/
b|c
  DB<64> print join "|",'abd' =~ /a(.+?)(c)?/
b|

well you seem to have other issues I can't see.

EDIT

Interesting

  DB<84> print join "|",'a<c1<c2' =~ /(.+?)<(c.)?/ # ok
a|c1

  DB<85> print join "|",'a<b1<b2' =~ /(.+?)<(c.)?/ # ok
a|

  DB<86> print join "|",'a<b1<c2' =~ /(.+?)<(c.)?/ # oops
a|

you might want to use use re 'debug' to parse whats happening.

update

ah now it's clearer

  DB<89> print join "|",'a<b1<c2' =~ /(.+?)(c.)?/
a|

The non-greedy is finishing as soon as it succeeds, and c. is optional