🧮 Calculator

Interactive calculator written in C with operation history and a custom expression processing pipeline.

✨ Features

• TUI
• Full expression evaluation with operator precedence
• Operation history tracking
• Input validation and sanitization
• Division by zero detection

⚙️ Processing pipeline

Every expression goes through a multi-stage pipeline before producing a result:

Raw Input → Sanitizer → Lexer → Parser → Result

Stage	Description
Sanitizer	Validates and cleans input — only digits, spaces, +-*/() allowed
Lexer	Tokenizes the expression using strtod for number parsing
Parser	Recursive descent parser with operator precedence, evaluates directly

🧪 Example

Input:  12 + 35 * (4 - 2)

Tokens: NUMBER(12) PLUS NUMBER(35) MULTIPLY LEFT_PAREN NUMBER(4) MINUS NUMBER(2) RIGHT_PAREN

Evaluation:
  4 - 2  = 2
  35 * 2 = 70
  12 + 70 = 82

Result: 82

📁 Project structure

├── main.c              # Entry point
├── cli.c / cli.h       # User interface (interactive menu)
├── sanitizer/          # Input validation
├── lexer/              # Tokenization
├── parser/             # Parsing and evaluation
├── history/            # Operation history
└── CMakeLists.txt      # Build configuration

🔢 Supported operations

Operation	Symbol
Addition	+
Subtraction	-
Multiplication	*
Division	/
Nested parentheses	()
Unary negation	-

Precedence order: () > unary - > * / > + -

🚀 Build and run

mkdir build && cd build
cmake ..
cmake --build .
./Calculator

📋 Requirements

• CMake 3.x+
• C11 compiler