Re: [Boost-users] [regex] Question about pattern

Boris wrote:

On Tue, 26 Feb 2008 22:37:19 +0200, wrote:

...

[...]I tried starting with a pattern like (C++ syntax for strings)

^(?:(<|<=|>|>=|=|<>){1}((?:-|\\+)?[0-9]+(?:\\.[0-9]+|\\,[0-9]+)?))?(?:\\s*)(?:(\\[FG:(?:BLUE|RED|GREEN|BLACK|YELLOW|WHITE|CYAN|NONE)\\])|(\\[BG:(?:BLUE|RED|GREEN|BLACK|YELLOW|WHITE|CYAN)\\])|(\\[FG:(?:BBLUE|RED|GREEN|BLACK|YELLOW|WHITE|CYAN|NONE)\\])(?:\\s*)(\\[BG:(?:BLUE|RED|GREEN|BLACK|YELLOW|WHITE|CYAN)\\])){1}$

But this does not allow the [fg:][bg:] terms to be interchanged and also when a new color or style will be added to the format class I have to change the pattern three times. I tried backward references with no success.

If regular expressions get as big as this and maybe even more complicated you might want to use Boost.Spirit instead. Boost.Spirit is not as easy to use as Boost.Regex but complicated expressions are broken down to something more easily understandable.

I second that suggestion. Any time input elements are not merely optional but order-insensitive, I start thinking "parser" rather than "regular expression."