Simple Terminal Calculator

A lightweight, high-performance math expression evaluator built in C++. It uses a custom Lexer, Recursive Descent Parser, and an Abstract Syntax Tree (AST) to process mathematical expressions with proper operator precedence.

🚀 Features

• Dual Mode: Use it as a one-off command-line tool or an interactive shell.
• AST-Based: Correctly handles operator precedence (multiplication before addition).
• Clean Output: Uses standard base-10 formatting for results.
• Zero Dependencies: Pure C++ using only the standard library.

• Operators support:
  • +-*/
  • ! (factorial)
  • ^ (power)
  • % (mod)
  • ()
  • -5 (negation supported)

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🛠 Usage

1. Interactive Mode

Run the program without arguments to enter the REPL (Read-Eval-Print Loop).

$ ./calc
> 5 + 5
 = 10
> 10 * 2 + 3
 = 23
> [Press Enter to Exit]

2. Direct Command Mode

Pass an expression as a string argument for a quick calculation.

$ ./calc "20 / 4 + 7"
12

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🏗 Architectural Flow

The calculator processes your input through three distinct stages:

1. Lexer: Breaks the raw string into tokens (Numbers, Operators, Parentheses).
2. Parser: Organizes tokens into an AST based on mathematical grammar.
3. Evaluator: Recursively traverses the tree to produce the final float result.

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🔨 Building with CMake

This project uses CMake for a portable build process. Follow these steps to build the executable:

# 1. Create a build directory
mkdir build && cd build

# 2. Configure the project
cmake ..

# 3. Build the executable
cmake --build .

The resulting calc binary will be located in the build directory.

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⚠️ Notes

• Precision: Uses float for evaluations.
• Error Handling: Returns NaN (Not a Number) if the parser fails to generate a valid root.
• Exiting: In interactive mode, simply press Enter on an empty line to quit.

👤 Author | ⚖️ License

Maks Makuta © 2026
No License - fell free to use that code in any way you need