Mathematical Expression Evaluator (A fancy way to say Calculator)

This TypeScript program evaluates a mathematical expression in infix notation and returns the result. It supports binary operations (+, -, *, /, ^) for basic arithmetic calculations, and some unary operations (!, sin, cos, tan).

-> The program converts the infix expression to Reverse Polish Notation (RPN) using the Shunting Yard Algorithm and then evaluates it either by constructing an Abstract Syntax Tree (AST) and collapsing the tree or by using stack calculations.

Functions

Tokenizer

The tokenizer function parses the input expression into individual tokens, such as operators, numeric literals, and Parenthesis.

Shunting Yard Algorithm

The sya function converts the infix expression into Reverse Polish Notation (RPN) using the Shunting Yard Algorithm. This algorithm handles operator precedence and associativity.

RPN Evaluation with AST

1. AST This function evaluates the RPN expression by constructing an Abstract Syntax Tree (AST) and collapsing the tree to compute the final result.

2. Stack Calculation This function evaluates the RPN expression using stack based calculations.

How is it used?

The program prompts you for a mathematical expression:

Enter a mathematical expression:
>> 4+5-3!*10*tan(5)^10

Or you can run it directly from the command line like this:

npm start "4+5-3!*10*tan(5)**10"

Note: When running npm start "<expression>" on windows, make sure to use ** for exponentiation instead of ^. This is because ^ acts as an escape character rather than an exponentiation operator.

It then outputs its Reverse Polish Notation and evaluates it with both AST and Stack Based calculations:

The Reverse Polish Notation of your expression:  4 5 + 3 ! 10 * 5 tan 10 ^ * -
Result from AST evaluation: -11694444.508011641
Result from RPN evaluation using stack calculation: -11694444.508011641

Tests

There are tests for the AST calculations, the RPN evaluation and the Shunting Yard Algorithm.