c - Evaluating mathematical expressions

Question

I am looking for an algorithm that I can use to evaluate mathematical expressions. I've seen a few questions on SO that are simmilar but the answers are C#/Delphi or python specific. I need to write the algorithm in C :)

The problem I am trying to solve is given a user input like

3*(2*x + 1)/x

I can evaluate the expression for any value of x.

What algorithms are available to do this? If you would like to suggest a library that already does this, then I would prefer a C library

Thank you

Answer 1

I asked Google for "recursive descent expression parser" (I don't blame you for not knowing what to look for) and found Parsing Expressions by Recursive Descent which provides an introduction to some useful parsing techniques.

Also, the Wikipedia article on Recursive descent parser includes a fairly complete example in C.