vertito wrote: > so > > cloudy mountainers > > will still be catched by ORing both of 2 expression, that would > produce AND expression, is that right? > /[\s']((mountain.*clouds)|(clouds.*mountain))[\s',-]/i will NOT match cloudy mountaineers. It will fail because of the [\s',-] at the end which REQUIRES a space, comma, dash or single quote. It would match cloudy mountain.
/((mountain.*clouds)|(clouds.*mountain))/i WILL match cloudy mountaineers.. There are no restrictions on what characters come before or after the expression. > so 2 expressions ORred together will have the same result as single ANDed > expression, right? > You can create the equivalent of an AND by ORing together two of the right expressions, yes. a AND b can be expressed as: (a THEN b) OR (b THEN a). a.*b will match a followed by b, with any number of any kind of character in between. It's half of an AND, in that it requires both to be present, but is order-specific in nature. If you want to match either order, you'd need to OR together a.*b and b.*a. Hence: /(a.*b)|(b.*a)/ The [\s',-] or \b's can be added to the beginning and end to force various kinds of word boundaries, if you wish to avoid matching substrings. I personally prefer \b for normal text. I'd only use something like [\s',-] if I wanted to restrict what kinds of things are a "word boundary".. ie: If I wanted to exclude period, colon, and other punctuation other than the ones in the expression. This kind of thing can be useful in a few cases where the kinds of punctuation that can be used are restricted, such as URLs or email addresses, but is not useful in general text processing.
