Building a Calculator — Putting It All Together

You've learned variables, conditionals, loops, functions, and collections. Now let's build a complete calculator application!

Project Overview

We'll build a calculator that:

• Shows a menu of operations
• Takes user input
• Performs calculations
• Handles errors gracefully
• Keeps a history of calculations

Step 1: Basic Structure

// calculator.adesh

fn main() {
    print("╔══════════════════════╗");
    print("║   ADESH CALCULATOR   ║");
    print("╚══════════════════════╝");
    print("");
    
    // TODO: Menu loop
}

Step 2: Operation Functions

fn add(a, b) { return a + b; }
fn subtract(a, b) { return a - b; }
fn multiply(a, b) { return a * b; }

fn divide(a, b) {
    if (b == 0) {
        return { ok: false, error: "Cannot divide by zero" };
    }
    return { ok: true, value: a / b };
}

fn power(a, b) {
    let result = 1;
    for i in 0..b {
        result = result * a;
    }
    return result;
}

fn modulo(a, b) {
    if (b == 0) {
        return { ok: false, error: "Cannot modulo by zero" };
    }
    return { ok: true, value: a % b };
}

Step 3: Menu System

fn show_menu() {
    print("┌──────────────────────┐");
    print("│   SELECT OPERATION   │");
    print("├──────────────────────┤");
    print("│ 1. Add (+)           │");
    print("│ 2. Subtract (-)      │");
    print("│ 3. Multiply (*)      │");
    print("│ 4. Divide (/)        │");
    print("│ 5. Power (^)         │");
    print("│ 6. Modulo (%)        │");
    print("│ 7. View History      │");
    print("│ 8. Clear History     │");
    print("│ 0. Exit              │");
    print("└──────────────────────┘");
}

fn get_choice() {
    // Simulated input (in real app, use input())
    let choice = 1;  // Change this to test different options
    return choice;
}

Step 4: Get Numbers from User

fn get_numbers() {
    // Simulated input
    let a = 10;
    let b = 5;
    return { a: a, b: b };
}

Step 5: Execute Operation

fn calculate(choice, a, b) {
    if (choice == 1) return { ok: true, value: add(a, b), symbol: "+" };
    if (choice == 2) return { ok: true, value: subtract(a, b), symbol: "-" };
    if (choice == 3) return { ok: true, value: multiply(a, b), symbol: "*" };
    if (choice == 4) return divide(a, b);
    if (choice == 5) return { ok: true, value: power(a, b), symbol: "^" };
    if (choice == 6) return modulo(a, b);
    return { ok: false, error: "Invalid operation" };
}

Step 6: History System

let history = [];

fn add_to_history(a, symbol, b, result) {
    let entry = {
        a: a,
        symbol: symbol,
        b: b,
        result: result,
        timestamp: "2024-01-15 10:30:00"  // Simulated
    };
    history.push(entry);
}

fn show_history() {
    if (len(history) == 0) {
        print("No calculations yet.");
        return;
    }
    
    print("┌─────────────────────────────────────┐");
    print("│         CALCULATION HISTORY         │");
    print("├─────────────────────────────────────┤");
    
    for i in 0..len(history) {
        let h = history[i];
        print(i + 1, ". ", h.a, " ", h.symbol, " ", h.b, " = ", h.result);
    }
    
    print("└─────────────────────────────────────┘");
}

fn clear_history() {
    history = [];
    print("History cleared.");
}

Step 7: Main Loop

fn main() {
    print("╔══════════════════════╗");
    print("║   ADESH CALCULATOR   ║");
    print("╚══════════════════════╝");
    print("");
    
    let running = true;
    
    while (running) {
        show_menu();
        let choice = get_choice();
        
        if (choice == 0) {
            print("Thank you for using Adesh Calculator!");
            running = false;
        } elif (choice == 7) {
            show_history();
        } elif (choice == 8) {
            clear_history();
        } elif (choice >= 1 && choice <= 6) {
            let nums = get_numbers();
            let result = calculate(choice, nums.a, nums.b);
            
            if (result.ok) {
                print("Result: ", nums.a, " ", result.symbol, " ", nums.b, " = ", result.value);
                add_to_history(nums.a, result.symbol, nums.b, result.value);
            } else {
                print("Error: ", result.error);
            }
        } else {
            print("Invalid choice. Please try again.");
        }
        
        print("");  // Empty line for readability
    }
}

Complete Working Version

Here's the full calculator you can run:

// calculator.adesh - Complete Calculator App

let history = [];

fn add(a, b) { return a + b; }
fn subtract(a, b) { return a - b; }
fn multiply(a, b) { return a * b; }

fn divide(a, b) {
    if (b == 0) return { ok: false, error: "Cannot divide by zero" };
    return { ok: true, value: a / b };
}

fn power(a, b) {
    let result = 1;
    for i in 0..b {
        result = result * a;
    }
    return result;
}

fn modulo(a, b) {
    if (b == 0) return { ok: false, error: "Cannot modulo by zero" };
    return { ok: true, value: a % b };
}

fn show_menu() {
    print("┌──────────────────────┐");
    print("│   SELECT OPERATION   │");
    print("├──────────────────────┤");
    print("│ 1. Add (+)           │");
    print("│ 2. Subtract (-)      │");
    print("│ 3. Multiply (*)      │");
    print("│ 4. Divide (/)        │");
    print("│ 5. Power (^)         │");
    print("│ 6. Modulo (%)        │");
    print("│ 7. View History      │");
    print("│ 8. Clear History     │");
    print("│ 0. Exit              │");
    print("└──────────────────────┘");
}

fn calculate(choice, a, b) {
    if (choice == 1) return { ok: true, value: add(a, b), symbol: "+" };
    if (choice == 2) return { ok: true, value: subtract(a, b), symbol: "-" };
    if (choice == 3) return { ok: true, value: multiply(a, b), symbol: "*" };
    if (choice == 4) return divide(a, b);
    if (choice == 5) return { ok: true, value: power(a, b), symbol: "^" };
    if (choice == 6) return modulo(a, b);
    return { ok: false, error: "Invalid operation" };
}

fn add_to_history(a, symbol, b, result) {
    history.push({ a: a, symbol: symbol, b: b, result: result });
}

fn show_history() {
    if (len(history) == 0) {
        print("No calculations yet.");
        return;
    }
    print("┌─────────────────────────────────────┐");
    print("│         CALCULATION HISTORY         │");
    print("├─────────────────────────────────────┤");
    for i in 0..len(history) {
        let h = history[i];
        print(i + 1, ". ", h.a, " ", h.symbol, " ", h.b, " = ", h.result);
    }
    print("└─────────────────────────────────────┘");
}

fn clear_history() {
    history = [];
    print("History cleared.");
}

// Demo runner (simulates user interaction)
fn run_demo() {
    let demo_choices = [1, 2, 3, 4, 5, 6, 4, 7, 0];
    let demo_numbers = [
        { a: 10, b: 5 },    // 10 + 5
        { a: 20, b: 8 },    // 20 - 8
        { a: 6, b: 7 },     // 6 * 7
        { a: 15, b: 3 },    // 15 / 3
        { a: 2, b: 8 },     // 2 ^ 8
        { a: 17, b: 5 },    // 17 % 5
        { a: 10, b: 0 },    // 10 / 0 (error)
    ];
    
    print("╔══════════════════════╗");
    print("║   ADESH CALCULATOR   ║");
    print("╚══════════════════════╝");
    print("");
    
    let num_idx = 0;
    
    for choice in demo_choices {
        show_menu();
        print("Choice:", choice);
        
        if (choice == 0) {
            print("Thank you for using Adesh Calculator!");
            break;
        } elif (choice == 7) {
            show_history();
        } elif (choice == 8) {
            clear_history();
        } elif (choice >= 1 && choice <= 6) {
            if (num_idx >= len(demo_numbers)) {
                print("Demo numbers exhausted");
                break;
            }
            
            let nums = demo_numbers[num_idx];
            num_idx = num_idx + 1;
            
            print("Input:", nums.a, "and", nums.b);
            let result = calculate(choice, nums.a, nums.b);
            
            if (result.ok) {
                print("Result: ", nums.a, " ", result.symbol, " ", nums.b, " = ", result.value);
                add_to_history(nums.a, result.symbol, nums.b, result.value);
            } else {
                print("Error: ", result.error);
            }
        } else {
            print("Invalid choice");
        }
        
        print("");
    }
}

run_demo();

Run It

Save as calculator.adesh and run:

adesh run calculator.adesh

Expected Output

╔══════════════════════╗
║   ADESH CALCULATOR   ║
╚══════════════════════╝

┌──────────────────────┐
│   SELECT OPERATION   │
├──────────────────────┤
│ 1. Add (+)           │
│ 2. Subtract (-)      │
│ 3. Multiply (*)      │
│ 4. Divide (/)        │
│ 5. Power (^)         │
│ 6. Modulo (%)        │
│ 7. View History      │
│ 8. Clear History     │
│ 0. Exit              │
└──────────────────────┘
Choice: 1
Input: 10 and 5
Result: 10 + 5 = 15

Choice: 2
Input: 20 and 8
Result: 20 - 8 = 12

Choice: 3
Input: 6 and 7
Result: 6 * 7 = 42

Choice: 4
Input: 15 and 3
Result: 15 / 3 = 5

Choice: 5
Input: 2 and 8
Result: 2 ^ 8 = 256

Choice: 6
Input: 17 and 5
Result: 17 % 5 = 2

Choice: 4
Input: 10 and 0
Error: Cannot divide by zero

Choice: 7
┌─────────────────────────────────────┐
│         CALCULATION HISTORY         │
├─────────────────────────────────────┤
1. 10 + 5 = 15
2. 20 - 8 = 12
3. 6 * 7 = 42
4. 15 / 3 = 5
5. 2 ^ 8 = 256
6. 17 % 5 = 2
└─────────────────────────────────────┘

Choice: 0
Thank you for using Adesh Calculator!

Key Concepts Used

Concept	Where Used
Variables	history, running, choice, nums
Functions	add, calculate, show_menu, etc.
Conditionals	if/elif/else in calculate and main loop
Loops	while (running) main loop, for in power and history
Arrays	history array, demo_choices
Objects	Operation results { ok, value, error }, history entries
Error Handling	Division by zero returns error object

Extensions to Try

1. Add More Operations

fn sqrt(a) { ... }
fn percent(a, b) { return a * b / 100; }

2. Scientific Mode

fn sin(a) { ... }
fn cos(a) { ... }
fn log(a) { ... }

3. Expression Parser

fn evaluate("2 + 3 * 4") { ... }  // Returns 14

4. Save/Load History

fn save_history() {
    // Write to file
    print(history, { file: "calc_history.json" });
}

fn load_history() {
    // Read from file
}

5. Real Input (when available)

fn get_choice() {
    print("Enter choice: ");
    return input();  // Future feature
}

fn get_numbers() {
    print("First number: ");
    let a = number(input());
    print("Second number: ");
    let b = number(input());
    return { a, b };
}

Summary

✅ You built a complete calculator with:

• Menu-driven interface
• 6 mathematical operations
• Error handling (division by zero)
• Calculation history
• Clean, organized code with functions

What You've Learned

┌─────────────────────────────────────────────────────────────┐
│                 LEARN PROGRAMMING SO FAR                    │
├─────────────────────────────────────────────────────────────┤
│  1. Hello World     →  First program, print, strings       │
│  2. Variables       →  let, types, mutability, arrays      │
│  3. Operators       →  + - * / %, == ===, ??, ?.          │
│  4. Conditionals    →  if/else, comparisons, logic         │
│  5. Loops           →  for/while, break/continue, patterns │
│  6. Functions       →  fn, parameters, return, closures    │
│  7. Higher-order    →  callbacks, factories, composition   │
│  8. Recursion       →  self-calls, tail calls, multiple ✅ │
│  9. Collections     →  arrays, objects, map/filter/reduce  │
│ 10. Calculator      →  Complete project integrating all    │
└─────────────────────────────────────────────────────────────┘

Where to Go Next

The calculator consolidated lessons 1–9. The course continues with text, types, and data modeling:

Path	Description
Next lesson	Strings & Text — interpolation, templates, methods
Language Guide	Basics — Deep dive into syntax
Memory Safety	Ownership — AdeshLang's superpower
OOP	Classes — Object-oriented programming
Async	Async/Await — Concurrent programming
Backends	Native JIT — 100x+ speedups
Examples	400+ examples — Learn by reading code

Final Challenge

Try building these on your own:

1. Todo List — Add, remove, mark complete, save to file
2. Number Guessing Game — Random number, hints, score tracking
3. Text Adventure — Rooms, items, commands, story
4. Expense Tracker — Categories, totals, monthly reports

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Congratulations! 🎉 You've completed the "Learn Programming with AdeshLang" tutorial series. You now have the foundation to build real applications. Keep coding, keep exploring, and remember:

आदेश (Adesh) — Give the command. The machine obeys.

Happy coding! 🚀