regex_search match but regex_match is not filled

[mickael@…]

Hi,

I face a problem with the regex_search function. If a piece of the subject match the pattern, and the matched string isn't at start of subject, then regex_search return true but the match_results is empty.

I attach a test case source.

Sorry for my english, I'm French ;)

[mickael@…]

Test case for the problem.

[John Maddock]

I believe this is a misunderstanding of how regular expressions work: if the expression is [a-z]* then it is perfectly legal to match a zero-length string if the * operator repeats zero times. So for example [a-z]* matched against the string " abc " can find 4 matches:

• the zero length string at the start of the " abc ".
• the string "abc".
• the zero length string after the "c".
• the zero length string at the end of " abc ".

When a zero length string is matched, then sub_match::first == sub_match::second and sub_matched::matched == true.

Probably you meant to use [a-z]+ as the regular expression?

If this doesn't clarify the issue, or if I've misunderstood, please reopen the ticket.

HTH & bonjour, John Maddock.

[mickael@…]

Bonjour :)

You're right, I misused regex_search. I correct my code to increment the start iterator when first == end, and add a test start != end before regex_search.

Even Boost::regex stress me a lot, its approach is great.

Thanks for your fastness !