I've been creating a web questionnaire (using the Forms Wizard module for mojoPortal CMS) that includes some questions where the answers were to be expressed as integer percentages. How to validate the responses? This was not quite as simple as I was hoping, as we need to use a RegularExpressionValidator and, as any fule kno, using regular expressions to solve a problem usually results in having two problems. So what's the expression? Of course regular expressions don't "understand" numbers, so it's not as simple as ^[0-100]$!

This expression seems to do the job without loopholes: ^([0-9]|[1-9][0-9]|100)$

If we want to permit decimals, then it gets more interesting. I'm no regexpert, but something like this should ensure we get either an integer from 0 to 100 or any decimal in between, with up to 2d.p. (also permitting 100.0 and 100.00!):

^100(\.[0]{1,2})?|([0-9]|[1-9][0-9])(\.[0-9]{1,2})?$

Spot any problems with these regular expressions...? Please comment and help me improve!