Basic CLI Calculator

A simple command-line calculator that performs basic arithmetic operations (addition, subtraction, multiplication, division) with support for decimal and negative numbers.

Features

• ✅ Addition, subtraction, multiplication, division
• ✅ Support for decimal numbers
• ✅ Support for negative numbers
• ✅ Error handling for division by zero
• ✅ Input validation with clear error messages
• ✅ Type hints on all functions
• ✅ Comprehensive test coverage

Installation

Prerequisites

• Python 3.8 or later
• uv package manager

Setup

# Clone the repository
git clone <repo-url>
cd sdd-basic-cli-calculator

# Create virtual environment and install dependencies
uv sync

# Activate virtual environment
source .venv/bin/activate  # On Windows: .venv\Scripts\activate

Usage

Basic Operations

# Addition
python -m src.cli 2 + 3
# Output: 5

# Subtraction
python -m src.cli 10 - 4
# Output: 6

# Multiplication
python -m src.cli 6 * 7
# Output: 42

# Division
python -m src.cli 20 / 4
# Output: 5

Decimal Numbers

python -m src.cli 3.5 + 2.1
# Output: 5.6

python -m src.cli 10.5 - 3.2
# Output: 7.3

Negative Numbers

python -m src.cli -5 + 3
# Output: -2

python -m src.cli 10 \* -2
# Output: -20

Error Handling

# Division by zero
python -m src.cli 10 / 0
# Output (stderr): Error: Division by zero
# Exit code: 1

# Invalid input
python -m src.cli abc + 5
# Output (stderr): Error: Invalid operand 'abc' - must be a number
# Exit code: 1

# Invalid operator
python -m src.cli 5 ^ 3
# Output (stderr): Error: Invalid operator '^' - must be one of: +, -, *, /
# Exit code: 1

# Missing arguments
python -m src.cli 5 +
# Output (stderr): Error: Invalid number of arguments - expected 3, got 2
# Exit code: 1

Development

Running Tests

# Run all tests
pytest

# Run with coverage
pytest --cov=src

# Run specific test file
pytest tests/unit/test_calculator.py

# Run with verbose output
pytest -v

Project Structure

src/
├── calculator.py       # Core calculator logic
└── cli.py             # CLI interface

tests/
├── unit/
│   └── test_calculator.py    # Unit tests
└── integration/
    └── test_cli.py           # Integration tests

pyproject.toml         # Project configuration

Code Style

All code includes type hints:

def add(a: float, b: float) -> float:
    """Add two numbers."""
    return a + b

Development Workflow

1. Write test first (Red)
2. Run test, verify it fails
3. Implement code (Green)
4. Run test, verify it passes
5. Refactor if needed (Refactor)
6. Commit with clear message

Architecture

Core Logic (src/calculator.py)

• Pure functions with no side effects
• All functions have type hints
• Each operation is independently testable
• Raises ValueError for invalid operations

CLI Interface (src/cli.py)

• Parses command-line arguments
• Validates input
• Calls appropriate calculator function
• Formats and displays results
• Handles errors gracefully

Testing

• Unit tests: Test calculator functions in isolation
• Integration tests: Test CLI with subprocess calls
• Coverage goal: >80% of code

License

MIT