numper

numper is a small calculator REPL written in C.

The project was built as practice for:

• tokenizing infix expressions
• converting infix to postfix with the shunting-yard algorithm
• evaluating postfix expressions with a stack
• writing low-level tests without hiding behind a framework the size of a small moon

Features

• integer and floating-point numbers
• unary + and -
• operators +, -, *, /, ^
• parentheses
• operator precedence and right-associative exponentiation
• test suite with parser, postfix, evaluator, and stack coverage

Build

make

Run

make run

Enter an expression at the prompt:

> 1+2*(3-1)
= 5
> -(1+2)^2
= -9

Type q to quit.

For tokenizer and postfix debug output:

./calc --debug

Test

make test

Supported Syntax

• numbers like 42, 3.14, .5, -2
• repeated unary signs like --3 or ---2
• unary minus before parentheses like -(1+2)

Limitations

• no functions like sin() or log()
• no variables
• no overflow handling
• division by zero follows the C math runtime
• expressions longer than the fixed stack size are rejected

Layout

• src/token.c: tokenizer
• src/postfix.c: infix to postfix conversion
• src/eval.c: postfix evaluator
• src/stack.c: generic stack storage helpers
• test/: unit tests