On Fri, 5 Apr 2002, Dr . Sharukh K . R . Pavri . wrote:
I think manish has already answered your questions correctly, I'll just add to that. > I downloaded your lecture on regex from the ACM website. I have a query; I am > a bit confused with the following lines from your examples. > > [A-Z^] - match anything from A-Z or ^ > [-A-Z] - match anything from A-Z or- > [+-*/] - match anything from + to * and / > [-+*/] - match - + * / square brackets mean match any one character within the square brackets. The ^ and - characters have special meaning inside square brackets. If - is not the first or last character, then it defines a range. ie, A-Z means from A to Z. You can have multiple ranges and intermix ranges with other lists, so you can do this: [0-9a-fA-F] to match a hex digit or even this: [abc0-9defA-EF] - both match the same. when - is not first or last, it matches a literal -. ^ when used as the first character in the class means invert the match. therefore, [^A-Z] means any character not in A-Z. Note, this is not the same as matching no character. There must necessarily be a character to match, and that character must be anything other than A-Z. the closing bracket also has special meaning for obvious reasons. To include a closing square bracket, put it as the first character in your class: []A-Z] opening square brackets don't have this problem. For square bracket and -, put the - last For inverted match on square bracket, there shouldn't be an issue, but I haven't tried it. Also, keep in mind that different regex engines interpret things differently. -- The primary function of the design engineer is to make things difficult for the fabricator and impossible for the serviceman. _______________________________________________ http://mm.ilug-bom.org.in/mailman/listinfo/linuxers
