regex - Validate mathematical expressions using regular expression?

Question

I want to validate mathematical expressions using regular expression. The mathematical expression can be this

1. It can be blank means nothing is entered

2. If specified it will always start with an operator + or - or * or / and will always be followed by a number that can have any number of digits and the number can be decimal(contains . in between the numbers) or integer(no '.' symbol within the number). examples : *0.9 , +22.36 , - 90 , / 0.36365

3. It can be then followed by what is mentioned in point 2 (above line). examples : *0.9+5 , +22.36*4/56.33 , -90+87.25/22 , /0.36365/4+2.33

Please help me out.

Answer 1

Something like this should work:

^([-+/*]d+(.d+)?)*

Regexr Demo

• ^ - beginning of the string
• [-+/*] - one of these operators
• d+ - one or more numbers
• (.d+)? - an optional dot followed by one or more numbers
• ()* - the whole expression repeated zero or more times