Mathematical Expression Parser

A C++ command-line calculator that leverages the shunting-yard algorithm for evaluating complex mathematical expressions, featuring variable storage and command history.

Building the Project

This project requires C++17 or above due to the use of features like std::optional and std::string_view.
To compile the project, use:

g++ -std=c++17 -I include src/*.cpp

The -std=c++17 flag is required to enable C++17 features. Run the resulting executable to start the calculator.

Features

Constants

The following mathematical constants are built-in:

• pi - Pi (3.14159...)
• e - Euler's number (2.71828...)
• phi - Golden ratio (1.61803...)
• sqrt2 - Square root of 2 (1.41421...)

Mathematical Functions

All functions require brackets for proper parsing:

• sin(x) - Sine (in degrees)
• cos(x) - Cosine (in degrees)
• tan(x) - Tangent (in degrees)
• log(x) - Base-10 logarithm
• ln(x) - Natural logarithm
• sqrt(x) - Square root

Operators

Supported mathematical operators in order of precedence:

1. ! - Factorial
2. ^ - Exponentiation
3. *, /, % - Multiplication, Division, Modulo
4. +, - - Addition, Subtraction

Implicit Multiplication

The parser supports implicit multiplication in various forms:

• -(2) evaluates to -2
• (2)(3) evaluates to 6
• 4(2-3) evaluates to -4
• (2-3)4 similarly evaluates to -4

Variable Management

Defining Variables

def [variable_name] [value]

Example:

def x 10
x + 5  # Evaluates to 15

Updating Variables

upd [variable_name] [value]

Example:

upd x ans  # Updates x to the last calculated result

Special Commands

Listing Information

• ls vars - Display all defined variables
• ls hist - Show calculation history

Deletion Commands

• del [variable_name] - Delete a specific variable
• del vars - Delete all variables
• del hist - Clear calculation history

Exit

• exit - Close the calculator

Important Notes

1. Trigonometric calculations are performed in degrees. Using radian values directly will not provide expected results.

2. Function calls can work without brackets for single numbers or variables, but brackets are recommended for clarity and required for expressions:

   sin(60)      # Correct, recommended
   sin 60       # Works for single numbers
   8(sin 30)    # Works, evaluates to 4
   sin 60/2     # Evaluates as (sin 60)/2 = 0.433, not sin(60/2)
   sin(60/2)    # Use brackets for expressions
   

3. The special variable ans always contains the result of the last calculation.

Examples

# Basic arithmetic
2 + 3 * 4     # Returns 14

# Using functions
sin(30)       # Returns 0.5
log(100)      # Returns 2

# Variable operations
def radius 5
pi * radius ^ 2  # Calculate area
def area ans     # saves computed value to area
ls vars          # Shows radius & area variables

# Updating variables
upd radius 10    # Updates radius
pi * radius ^ 2  #find new area
upd area ans     #area takes new value

# Implicit multiplication
2(3+4)        # Returns 14

Error Handling

The parser includes error handling for:

• Invalid syntax
• Undefined variables
• Division by zero
• Invalid function arguments
• Malformed expressions

If an error occurs, an appropriate error message will be displayed, and the calculator will continue running.
Working on more features and a better GUI. If you have recommendations, pm me, add issue or fork this and add your idea.