Tiny_Math_Parser

A 99-lines math expressions parser made from scratch. No package has been used.

Usage

Pre-conditions

This parser does not support variables. The elements of the expression have to be seperated by a whitespace.

Execution

You can feed the expression into the parser by passing it as an argument the moment of the execution of the script.

Sample:

python parser.py '5 + ( 1 + 2 * 1 )'

output: 8.0

Methodology

I did use the recursive descent method that is widely used for it being one of the most optimal ways of evaluating nested mathematical expressions.

The script is an implementation of the following grammar:

parse -> low_priority_terms_trigger

low_priority_terms_trigger -> high_prio_terms_trigger low_priority_terms

low_priority_terms -> + high_prio_terms_trigger low_priority_terms
    | - high_prio_terms_trigger low_priority_terms
    | epsilon

high_prio_terms_trigger -> FACTOR high_priority_terms

high_priority_terms -> * FACTOR high_priority_terms | 
    / FACTOR high_priority_terms | epsilon

FACTOR -> x | (parse)