Expression interpreter written in Python

Last update: Oct 17, 2021

Overview

Calc Interpreter

An interpreter modeled after a calculator implemented in Python 3. The program currently only supports basic mathematical expressions. The package uses Reverse Polish Notation also known as postfix expression internally to easily represent mathematical expressions. This is powerful as it allows operators to be organised in such a way that precedence is absolute meaning an operator that is encountered first will always be executed first.

However, it is obvious that postfix is not normal or rather not usually taught in schools and thus infix expression is still the way for the user to write expressions. The interpreter uses a modified Shunting-Yard algorithm to produce Abstract Syntax Trees. Evaluation of ASTs is trivial, and they are flexible making it easy to extend the grammar and functionality later on.

Installation

The package is available in PyPI and can be installed via pip.

pip install expr-calc
#or
python3 -m pip install expr-calc

Usage

The best way to run the program currently is to execute the REPL and can be done in a python file or through your terminal.

Assuming your present working directory is inside the cloned repo, you can run the following command without the comment.

# inside /clone_path/expr_calc/
python -m expr_calc

The test suite can also be ran with pytest when inside the cloned repo

pytest  # or python -m pytest

Example

Once inside the REPL, you can start evaluating expressions. Currently, only operators listed in Features are supported.

calc> 1 + 1
2

calc> 345--500
845

calc> -2
-2

calc> 123 ^ 4
228886641

calc> 32 / 1.5
21.33333333333333333333333333

calc> 123 * 456
56088

calc> 34 % 5
4

calc> 4 ^ 1/2
0.5

calc> 4 ^ (1/2)
2.0

Features

Infix expressions
Basic operators such as +, -, *, /, %, ^
Tokens created from an expression can also be fetched to be manipulated if one wanted to do so
Expressions are transformed into m-ary Tree objects connected to each other

Features I want to add later

variable support
custom functions
more mathematical functions such as sin, cos, tan, etc
and possibly a simple symbolic computation support

Resources

Structural basis for solubility in protein expression systems

Structural basis for solubility in protein expression systems Large-scale protein production for biotechnology and biopharmaceutical applications rely

16 Aug 18, 2022

PyDy, short for Python Dynamics, is a tool kit written in the Python

PyDy, short for Python Dynamics, is a tool kit written in the Python programming language that utilizes an array of scientific programs to enable the study of multibody dynamics. The goal is to have a modular framework and eventually a physics abstraction layer which utilizes a variety of backends that can provide the user with their desired workflow

307 Jan 1, 2023

Simple, high-school-leveled sequence library written in Python / 간단한 고등학교 수준 수열 라이브러리 (Python)

Simple, high-school-leveled sequence library written in Python

1 Dec 8, 2021

Msgpack serialization/deserialization library for Python, written in Rust using PyO3 and rust-msgpack. Reboot of orjson. msgpack.org[Python]

ormsgpack ormsgpack is a fast msgpack library for Python. It is a fork/reboot of orjson It serializes faster than msgpack-python and deserializes a bi

139 Dec 30, 2022

Synthetik Python Mod - A save editor tool for the game Synthetik written in python

Synthetik_Python_Mod A save editor tool for the game Synthetik written in python

2 Sep 10, 2022

MiniJVM is simple java virtual machine written by python language, it can load class file from file system and run it.

MiniJVM MiniJVM是一款使用python编写的简易JVM，能够从本地加载class文件并且执行绝大多数指令。支持的功能 1.从本地磁盘加载class并解析 2.支持绝大多数指令集的执行 3.支持虚拟机内存分区以及对象的创建 4.支持方法的调用和参数传递 5.支持静态代码块的初始化不支

60 Apr 1, 2022

Pygments is a generic syntax highlighter written in Python

Welcome to Pygments This is the source of Pygments. It is a generic syntax highlighter written in Python that supports over 500 languages and text for

1.2k Jan 6, 2023

Retrying is an Apache 2.0 licensed general-purpose retrying library, written in Python, to simplify the task of adding retry behavior to just about anything.

Retrying Retrying is an Apache 2.0 licensed general-purpose retrying library, written in Python, to simplify the task of adding retry behavior to just

1.9k Dec 29, 2022

A full-featured, hackable tiling window manager written and configured in Python

A full-featured, hackable tiling window manager written and configured in Python Features Simple, small and extensible. It's easy to write your own la

3.8k Dec 31, 2022

Comments

Better lexing(and scanning) and parsing
There is currently an issue with the lexing strategy for unary operators. Because i have only partially implemented it, constructs that uses unary operators are note exactly recognised. For example

> -(1) 1 # should be -1

This is problematic because it affects expressions such as to give wrong the answer

> -1^2 1 # should be -1 > -(1^2) 1 # should be -1

The main reason for this is that unary operators are not actually lexed themselves, when an expression such as -1 is passed, the program checks if the immediately succeeding character is a number and immediately binds the sign to the number after it, a bracket/parentheses is not a number and thus the operator doesn't get lexed independently at all disabling the parser to not recognise have any knowledge of it.

Also note that + and - are always initially tokenised as Token.BINARY_OPs and I believe this should change.

see this line
bug enhancement
opened by lestherll 2
Support for high precision floating-points
Currently, the interpreter uses raw Python as the engine for evaluating mathematical expressions. This is good in normal cases but as you may already know, computers aren't so good at dealing with high precision floating-points. It would be good to be able to utilise perhaps some module to deal with this.

> 9.999999800000001 * 10^15 9999999800000002.0 # should be 9999999800000001
bug enhancement
opened by lestherll 0
Create custom error codes
Currently, there are no custom error codes. Adding one would make the project more concrete and robust.

Example

# inside REPL > 1.1.1 SyntaxError: Numbers can only have one decimal point
enhancement
opened by lestherll 0

Releases(v0.1.2)

v0.1.2(Sep 7, 2021)

Source code(tar.gz)
Source code(zip)

Owner

BSc Comp Sci at Newcastle University

GitHub Repository

Streamlit apps done following data professor's course on YouTube

streamlit-twelve-apps Streamlit apps done following data professor's course on YouTube Español Curso de apps de data science hecho por Data Professor

1 Jan 10, 2022

ThinkPHP全日志扫描工具，命令行版和BurpSuite插件版

ThinkPHP3和5日志扫描工具，提供命令行版和BurpSuite插件版，尽可能全的发掘网站日志信息命令行版安装 git clone https://github.com/r3change/TPLogScan.git cd TPLogScan/ pip install -r requireme

119 Dec 27, 2022

Procscan is a quick and dirty python script used to look for potentially dangerous api call patterns in a Procmon PML file.

PROCSCAN Procscan is a quick and dirty python script used to look for potentially dangerous api call patterns in a Procmon PML file. Installation git

9 Sep 02, 2022

Plugins for Agisoft Metashape

Данные плагины предназначены для расширения функциональных возможностей Agisoft Metashape. Плагины представляют собой отдельные программы с собственным интерфейсом, которые запускаются внутри Agisoft

17 Dec 10, 2022

Graphene Metanode is a locally hosted node for one account and several trading pairs, which uses minimal RAM resources.

Graphene Metanode is a locally hosted node for one account and several trading pairs, which uses minimal RAM resources. It provides the necessary user stream data and order book data for trading in a

5 May 08, 2022

Registro Online (100% Python-Mysql)

Registro elettronico scritto in python, utilizzando database Mysql e Collegando Registro elettronico scritto in PHP

1 Dec 20, 2021

This code makes the logs provided by Fiddler proxy of the Google Analytics events coming from iOS more readable.

GA-beautifier-iOS This code makes the logs provided by Fiddler proxy of the Google Analytics events coming from iOS more readable. To run it, create a

3 Feb 02, 2022

Python plugin for Krita that assists with making python plugins for Krita

Krita-PythonPluginDeveloperTools Python plugin for Krita that assists with making python plugins for Krita Introducing Python Plugin developer Tools!

18 Dec 01, 2022

Your E-Canteen that is convenient and accessible wherever you are in the campus

Food Web E-Canteen System Your E-Canteen that is convenient and accessible wherever you are in the campus. Table of Contents About The Project Contrib

5 Jan 07, 2023

Use Fofa、shodan、zoomeye、360quake to collect information(e.g:domain,IP,CMS,OS)同时调用Fofa、shodan、zoomeye、360quake四个网络空间测绘API完成红队信息收集

Cyberspace Map API English/中文 Development fofaAPI Completed zoomeyeAPI shodanAPI regular 360 quakeAPI Completed Difficulty APIs uses different inputs

61 Oct 08, 2022

Expression interpreter written in Python

Related tags

Overview

Calc Interpreter

Installation

Usage

Example

Features

Features I want to add later

Resources

You might also like...

Structural basis for solubility in protein expression systems

PyDy, short for Python Dynamics, is a tool kit written in the Python

Simple, high-school-leveled sequence library written in Python / 간단한 고등학교 수준 수열 라이브러리 (Python)

Msgpack serialization/deserialization library for Python, written in Rust using PyO3 and rust-msgpack. Reboot of orjson. msgpack.org[Python]

Synthetik Python Mod - A save editor tool for the game Synthetik written in python

MiniJVM is simple java virtual machine written by python language, it can load class file from file system and run it.

Pygments is a generic syntax highlighter written in Python

Retrying is an Apache 2.0 licensed general-purpose retrying library, written in Python, to simplify the task of adding retry behavior to just about anything.

A full-featured, hackable tiling window manager written and configured in Python

Comments

Better lexing(and scanning) and parsing

Support for high precision floating-points

Create custom error codes

Example

Releases(v0.1.2)

v0.1.2(Sep 7, 2021)

Owner

Streamlit apps done following data professor's course on YouTube

ThinkPHP全日志扫描工具，命令行版和BurpSuite插件版

Procscan is a quick and dirty python script used to look for potentially dangerous api call patterns in a Procmon PML file.

Plugins for Agisoft Metashape

Graphene Metanode is a locally hosted node for one account and several trading pairs, which uses minimal RAM resources.

Registro Online (100% Python-Mysql)

This code makes the logs provided by Fiddler proxy of the Google Analytics events coming from iOS more readable.

Python plugin for Krita that assists with making python plugins for Krita

Your E-Canteen that is convenient and accessible wherever you are in the campus

Use Fofa、shodan、zoomeye、360quake to collect information(e.g:domain,IP,CMS,OS)同时调用Fofa、shodan、zoomeye、360quake四个网络空间测绘API完成红队信息收集

Awesome Casino is simple offline casino made on python.

Reactjs web app written entirely in python, using transcrypt compiler.

E5 自动续期

Headless chatbot that detects spam and posts links to it to chatrooms for quick deletion.

Gerador do Arquivo Magnético Sintegra em Python

Tucan Discord Token Generator - Remastered

A module to prevent invites and joins to Matrix rooms by checking the involved server(s)' domain.

A Python 3 client for the beanstalkd work queue

Moji sends text and fun facts from different APIs wit da use of a notification deamon

Auto-ropper is a tool that aims to automate the exploitation of ROP.