Hossin-Azmoud / Expr

An arithmetic expression parser in Python

exp_parser

An arithmetic expression parser in Python

Idea desc

• So basically I had a programming language implementation that I was working on click here and now I realized that I need to study more about the topic of parsing expressions, so this repo is like an experiment so I can get how much hard or easy it actually is to parse expressions in python before integrating this concept into the language.

Quick start

$ git clone https://github.com/Moody0101-X/exp_parser
$ cd exp_parser\src
$ python main.py

main goal

• the main goal of this parser is just for short parsing and evaluating arithmetic expressions such as (x + 1) * (6 * 20) or 1 + 2 * 2 - 20 * (-10)..
• making a REPLE to give expressions and get answers from scratch, no libs and no plugin just python built-in functions and string manipulation.
• REPLE front-end:

$ REPLE > (1 + 1)
ans: 2

$ REPLE > (1 + 1) * (2 * 2)
ans: 8

Define functions

• u can define functions using Func keyword

$ REPLE > Func increment(a, b) => |(a + 1) + (b + 1)|
$ REPLE > increment(1, 3)
ans: 6

Define variables

• u can define functions using Func keyword

$ REPLE > x = 69
$ REPLE > x
ans: 69

• NOTE: ans is a special variable which is assigned to latest computed result. type ans to access it!

What data structure I think I will use for this

• Stacks: for simple calculations

Resources

• Shunting yard algorithm
• Shunting yard algorithm 2
• Evaluating the postfix expression