Hi I have to split a regular expression of the shape (simplified for this example) (?:\<(or)\>)|((?:[[:word:]]+)[[:blank:]]*(?=\()) the idea is to match (actually with regex_search algorithm) or as a keyword and to match function names in function invocations (or declarations); i.e., or ( should be matched as the keyword "or" and then a parenthesis, but foo ( "foo" should be matched as a function name the above expression works correctly (and I've always used that one). Now, I had to split that expression into two regular expressions (?:\<(or)\>) ((?:[[:word:]]+)[[:blank:]]*(?=\()) and try to match the above situations the same way. Thus, I'm trying to match each one and then take the one that matched first with the biggest length (and smallest prefix but this is not important now); of course I don't get the desired behavior, since in or ( "or" is matched as a function name. Thus I was wondering: which is the actual algorithm used by regex_search? Does it take into consideration other things beside the biggest length? thanks in advance Lorenzo -- Lorenzo Bettini, PhD in Computer Science, DSI, Univ. di Firenze ICQ# lbetto, 16080134 (GNU/Linux User # 158233) HOME: http://www.lorenzobettini.it MUSIC: http://www.purplesucker.com BLOGS: http://tronprog.blogspot.com http://longlivemusic.blogspot.com http://www.gnu.org/software/src-highlite http://www.gnu.org/software/gengetopt http://www.gnu.org/software/gengen http://doublecpp.sourceforge.net