alexeyhorkin/arithmetic-expressions

Calculator for arithmetic expressions

In this repository, I considered a parsing algorithm using recursive descent for a context-free LL(1) grammar of the language of arithmetic expressions. I use Top-Down parser to create an expression tree.

Based on this idea:

Grammar for arithmetic expressions:

Getting Started

Prerequisites

I use Python3.7.0 or higher, so first of all we need to install some python packages so that we can run tests and check types as well.

pip install -r requirements.txt

Installing

Simply run:

pip install .

Running the tests

Tests based on Pytest fraimwork, to run all tests, enter:

pytest ./tests/

Sample Tests

The tests in the section tests / test_calculation are needed to check the correctness of the calculation of arithmetic expressions. A few simple test cases:

CASES = [CaseCalc("1", 1),
         CaseCalc("1 + 2", 3),
         CaseCalc("1 - 2", -1)]

Style test

To check code style i use flake8 and mypy for typings. Run the following command to start checking

• for PEP8 code style:

flake8 . --count --select=E9,F63,F7,F82 --show-source --statistics

• for typing:

mypy ./

License

This project is licensed under the MIT

arithmetic-expressions's Issues

No input validation

Have to implement input validation "on fly" during parsing an expression