Regular expression for validating a number
I’ll provide a few different methods to handle the actual validation through Regular Expressions and let you determine which one might best suit your needs.
But the input number must be in a range from -2055 to 2055 and I want to check this by using regular expression. :5[0-5] //50 through 55 | //or [0-4][0-9]) //00 through 49 | //or 1[0-9] //a one followed by any three digits | //or [1-9][0-9] //1-9 followed by 0 through 2 of any digit | //or (? It's an interesting exercise, because you can think of two distinct method: roughly, you can either: Without trying, how would you know which is best? (With thanks to Plasma Power and Casimir et Hippolyte for the debugging assistance.) Depending on what you are capturing, it is likely that all sub-groups should be made into non-capture groups. It turns out that the first approach (aliteralmind's answer) is far more economical. Speed Tests Here is the output of my simple speed test, matching from -1M to 1M. Compilers use Regular Expressions to validate the syntax of programs.If the program code does not match the Regular Expression then the compiler indicates that there is a syntax error. When a user clicks the OK button, the program checks to ensure that none of the fields are empty.