pycalc/README.md

# Pycalc

**Pycalc** is a simple expression calculator. It can evaluate mathematical expressions, and output the result of the evaluation.

## How it works
1. Scan the expression
	- Check for malformed expression and invalid characters
	- Tokenize the expression (I wrote a custom parser to do this)
  2. If there are any parantheses, replace the parantheses with the result of the sub-expression.
  3. Evaluate the overall expression (which should no longer have any parantheses)

Rather than building a tree from the expression (which is the recommended approach), I have opted to perform the substitutions in-place. This means that the result of an operation replaces the operation itself. 

The reason I chose to do this, is that my parsing algorithm considers everything inside parantheses as a single token. Therefore, it is fairly easy to replace this token with the result of the expression within the parantheses.

## Features
- Order of operations
- Arbitrary whitespace
- Parantheses
- Simple error checking

## To-do
- ~~Simple algebraic parsing (assign values to variables, etc.)~~
- More robust error-checking