This is just a math expression evaluator in C that I wrote for fun and learning. If you want a production-quality library, take a look at TinyExpr.

The Shunting-yard algorithm is used for parsing expressions written in Infix notation (e.g. 5 + 3). My implementation parses operators and operands and store each type in a separate stack (ops_stack and operands_stack) for ease of computation, and doesn't provide a function to produce an expression in Reverse Polish notation yet.

To use as a library, copy the necessary sources (all but demo.c, debug.*, tests.c) to your project and include evaluate.h. See evaluate.h for some docs and demo.c for a usage example.

• demo.c a simple calculator built using the library.
• evaluate.c uses the Shunting-yard algorithm to evaluate expressions written in infix notation.
• ops.c defines the supported operations.
• stack.h is a stack implementation to support the algorithm. It's based on the vector.h file, which I originally wrote for use in my C utilities, so it's generic (i.e macro hell).
• debug.c prints some debugging info when the EVAL_DEBUG macro is defined.
• tests.c: some tests

To build and run the demo, run:

make demo

To run tests:

make tests

• More operations and constants
• Explore more algorithms for mathematical expression parsing
• Rust version
• Use an arbitrary-precision arithmetic library to save myself from headaches
• Operator associativity. Currently, the exponentiation operator (^) is special-cased to be right-associative. If I'll ever add more right-associative operators, I should modify the operator struct to store associativity and remove the special case.