Currency Regular Expression
regex
Solution
You can express "between one and six digits; comma before the last three digits is optional" a bit more tersely as `\d{1,3}(,?\d{3})?`. This also allows you to include only two copies of `(\.\d{1,2})?`: one for positive and one for negative, instead of one for positive-without-comma, one for positive-with-comma, etc.
Also, `\d{1,2}` can be shortened slightly to `\d\d?`, though I'm not sure if that's an improvement.
So, barring some notation like `(?(1))` to test if a backreference is set, here's the shortest version I see:
^(\$?\d{1,3}(,?\d{3})?(\.\d\d?)?|\(\$?\d{1,3}(,?\d{3})?(\.\d\d?)?\))$
One perhaps-undesirable aspect of your regex, and of this one, is that they will allow something like `$00,012.7`, even though no one uses leading zeroes that way. You can address that by requiring the first digit to be nonzero, and then adding a special case to handle `$0` and `(0.12)` and so on:
^(\$?(0|[1-9]\d{0,2}(,?\d{3})?)(\.\d\d?)?|\(\$?(0|[1-9]\d{0,2}(,?\d{3})?)(\.\d\d?)?\))$
Edited to add: using a lookahead assertion like F.J suggests in his/her answer, the latter can be shortened to:
^(?!\(.*[^)]$|[^(].*\)$)\(?\$?(0|[1-9]\d{0,2}(,?\d{3})?)(\.\d\d?)?\)?$
Problem
I think I created a working regular expression for what I need. Just wondering if anyone can break it or see a shorter way to write it. The regular expression should validate the following... - Dollar sign optional - Negative numbers signified with parenthesis, not a minus - If negative, dollar sign should be outside the parenthesis - Commas are optional - Max number is 999999.99 - Min number is (999999.99) - Decimals do not have to be supplied, but if so, no more than two digits So here are some examples of valid ones... ``` 9 $9 $0.99 ($999,999.99) (999999) ($999999) (999,999) 99,999.9 ``` This is what I have come up with: ``` ^\$?(((\d{1,6}(\.\d{1,2})?)|(\d{1,3},\d{3}(\.\d{1,2})?)|\(((\d{1,6}(\.\d{1,2})?)|(\d{1,3},\d{3}(\.\d{1,2})?))\)))$ ``` CORRECTION, my spec was wrong, if the dollar sign is used it must be INSIDE the parenthesis.