Calculator Example

A fully functional calculator built with CocoaGUI demonstrating button handling, state management, and user interaction.

Layout

┌─────────────────────────────────┐
│  Simple Calculator              │
├─────────────────────────────────┤
│                                 │
│  ┌─────────────────────────┐    │
│  │ 0                       │    │
│  └─────────────────────────┘    │
│                                 │
│   [7]  [8]  [9]         [+]     │
│   [4]  [5]  [6]         [-]     │
│   [1]  [2]  [3]         [*]     │
│   [0]  [.]  [=]         [/]     │
│                                 │
│        [Clear]                  │
└─────────────────────────────────┘

Complete Code

"""
Simple Calculator Application
Using the CocoaGUI GUI Library
"""

import CocoaGUI as gui

# Create the main window
app = gui.Window("Simple Calculator", width=350, height=450)

# Title label
gui.Label(app, "Simple Calculator", x=90, y=20, size=18)

# Display area for the calculation
display = gui.TextArea(app, x=25, y=60, width=300, height=60)
display.set("0")

# Global variable to track calculation state
current_value = ""
operator = None
first_number = None

def add_to_display(value):
    """Add a number or decimal to the display"""
    global current_value
    current_text = display.get().strip()

    if current_text == "0" or current_text == "Error":
        current_value = str(value)
    else:
        current_value = current_text + str(value)

    display.set(current_value)

def clear_display():
    """Clear the calculator display"""
    global current_value, operator, first_number
    current_value = ""
    operator = None
    first_number = None
    display.set("0")

def set_operator(op):
    """Set the mathematical operator"""
    global operator, first_number, current_value
    current_text = display.get().strip()

    try:
        first_number = float(current_text)
        operator = op
        current_value = ""
        display.set(f"{first_number} {op}")
    except:
        display.set("Error")

def calculate():
    """Perform the calculation"""
    global first_number, operator, current_value

    if first_number is None or operator is None:
        return

    current_text = display.get().strip()

    # Extract the second number from display
    try:
        parts = current_text.split(operator)
        if len(parts) > 1 and parts[1].strip():
            second_number = float(parts[1].strip())
        else:
            return

        # Perform calculation
        if operator == "+":
            result = first_number + second_number
        elif operator == "-":
            result = first_number - second_number
        elif operator == "*":
            result = first_number * second_number
        elif operator == "/":
            if second_number == 0:
                display.set("Error: Division by zero")
                first_number = None
                operator = None
                return
            result = first_number / second_number

        # Display result
        display.set(str(result))
        first_number = result
        operator = None
        current_value = str(result)
    except:
        display.set("Error")
        first_number = None
        operator = None

# Number buttons - ultra simple syntax!
button_positions = [
    (7, 25, 150), (8, 100, 150), (9, 175, 150),
    (4, 25, 200), (5, 100, 200), (6, 175, 200),
    (1, 25, 250), (2, 100, 250), (3, 175, 250),
    (0, 25, 300)
]

for num, x, y in button_positions:
    gui.Button(app, str(num), command=lambda n=num: add_to_display(n), x=x, y=y)

# Decimal point button
gui.Button(app, ".", command=lambda: add_to_display("."), x=100, y=300)

# Operator buttons
gui.Button(app, "+", command=lambda: set_operator("+"), x=250, y=150)
gui.Button(app, "-", command=lambda: set_operator("-"), x=250, y=200)
gui.Button(app, "*", command=lambda: set_operator("*"), x=250, y=250)
gui.Button(app, "/", command=lambda: set_operator("/"), x=250, y=300)

# Equals button
gui.Button(app, "=", command=calculate, x=175, y=300)

# Clear button
gui.Button(app, "Clear", command=clear_display, x=25, y=360)

# Info label
gui.Label(app, "Created with CocoaGUI GUI Library", x=60, y=415, size=10)

# Run the application
app.run()

Key Features

State Management

The calculator maintains three pieces of state: - current_value: The number being typed - operator: The selected operation (+, -, *, /) - first_number: The first operand

Error Handling

Division by zero detection
Invalid input handling
Error state recovery with Clear button

User Experience

Clear visual feedback
Decimal point support
Continuous calculations (result becomes first number)

How It Works

1. Number Input

When you click a number button:

def add_to_display(value):
    # Appends digit to current display
    # Handles "0" and "Error" states

2. Operator Selection

When you click an operator:

def set_operator(op):
    # Stores the first number
    # Shows the operation in display
    # Prepares for second number

3. Calculation

When you click equals:

def calculate():
    # Extracts second number from display
    # Performs the operation
    # Shows result
    # Allows chaining operations

4. Clear Function

Resets all state:

def clear_display():
    # Resets all variables
    # Sets display to "0"

Improvements You Could Make

Keyboard Support: Add keyboard event handlers
History: Keep track of previous calculations
Advanced Operations: Add sqrt, power, percentage
Better Layout: Use calculated positions instead of hardcoded
Styling: Customize button colors and sizes

Learning Points

This example demonstrates: - ✅ Managing application state with global variables - ✅ Using lambda functions for button commands - ✅ Creating multiple similar widgets with loops - ✅ Error handling in user interactions - ✅ String parsing and type conversion - ✅ Building a complete, functional application

Try It Yourself

Challenge 1: Add a backspace button to delete the last digit

Challenge 2: Add support for negative numbers

Challenge 3: Show calculation history in a TextArea

Challenge 4: Add memory functions (M+, M-, MR, MC)