How to differentiate '-' operator from a negative number for a tokenizer

Question

I am creating an infix expression parser, an so I have to create a tokenizer. It works well, except for one thing: I do not now how to differentiate negative number from the

Answer 1

In the first example the tokens should be 23, /, - and 23.

The solution then is to evaluate the tokens according to the rules of associativity and precedence. - cannot bind to / but it can to 23, for example.

If you encounter --56, is split into -,-,56 and the rules take care of the problem. There is no need for special cases.