Math equation tokenization

Looking for a library that will tokenize a math-"oriented" string. I know of GNU Bison/flex, and have also found this: GNU libmatheval - GNU Project - Free Software Foundation (FSF).

Really, I either need some decent reading material on parsing/tokenizing or a simpler library that will take something like "a = 5*4/(3+2*somefunc(5));" and split it up by the operators.

Thanks in advance for any suggestions.

Using Regular Expressions for Lexical Analysis is helpful, but I suck at regular expressions.