Validate mathematical Equation

Question

I'm trying to write regular expression which ensure that mathematical equation syntax is true I tried many times but I didn't get what I want.

I need your help to find a regular expression to handle the following cases:

op1 = op2 [+-*/%^] number or op3*

allow nesting brackets

op1 = (op2 [+-*/%^] ( op3 [+-*/%^] op4 ) ) [+-*/%^] op5 or number*

And also allow merge of both Expressions and allow spaces between operands and operations

If your regex engine does not support recursive regexes, you are out of luck. Validate them with a recursive descent algorithm. Maybe you get lucky by counting the parentheses and validating each term with a regex, but that's bound to miss some cornercases. — knittl, Oct 31 '13 at 11:23
Have a look at this question: http://stackoverflow.com/questions/355062/is-there-a-string-math-evaluator-in-net — germi, Oct 31 '13 at 11:30
.NET Regex engine allowes for recursivity through balancing groups. — Pierluc SS, Oct 31 '13 at 11:58
@knittl: C# and .net in general support recursion and have a stack system. — Casimir et Hippolyte, Oct 31 '13 at 11:59
@CasimiretHippolyte it means we are all glad you are here to tell us that .net operates with a stack. knittl was referring to the regex engine itself. — Gusdor, Oct 31 '13 at 13:08
@Gusdor: Sorry, I was speaking about the regex engine itself. — Casimir et Hippolyte, Oct 31 '13 at 13:09
The takeaway here is though some so called regular expression libraries support that kind of matching, you'd be better off writing your own lexer and parser. — Eric Lippert, Nov 01 '13 at 14:35

score 2 · Accepted Answer · answered Apr 28 '14 at 11:15

2

I tried do this with regular Expression but This was very hard, I make Equation validation using Stacks and it works fine

answered Apr 28 '14 at 11:15

Ahmed Ghazey

score 1 · Answer 2 · answered Oct 31 '13 at 13:21

1

You can do this through balancing groups, you can read the following article for a good demo and explanation of balancing groups.

answered Oct 31 '13 at 13:21

Pierluc SS

2 Answers2