Hello, World!

Chapter Status: ✅ 100% Working (8/8 examples)

Last updated: 2025-08-24
Ruchy version: ruchy 3.169.0

“I still remember the first time I made a computer print ‘Hello, World!’ It was magical - like teaching a very literal friend to speak. That same feeling of wonder drove me to create Ruchy, where your first program works immediately, not after hours of setup.” - Noah Gift

The Problem

Every programming journey begins with a simple question: “How do I make the computer say something?” The “Hello, World!” program is more than tradition—it’s your first proof that you can communicate with a computer in its own language.

In Ruchy, we believe this first step should be immediate and rewarding, not buried under complexity.

Quick Example

Here’s your first Ruchy program:

fun main() {
    println("Hello, World!");
}

That’s it! Save this in a file called hello.ruchy and run it with:

$ ruchy run hello.ruchy
Hello, World!

Or try it instantly in the REPL:

$ ruchy repl
>>> println("Hello, World!")
Hello, World!

Core Concepts

The println Function

println is Ruchy’s built-in function for printing text to the screen. It:

• Takes any number of arguments
• Prints them separated by spaces
• Automatically adds a newline at the end
• Returns () (unit type) when done

String Literals

In "Hello, World!":

• Double quotes " mark the beginning and end of text
• Everything inside is treated literally as text
• This creates a str type in Ruchy

Function Calls

The syntax println(...) is a function call:

• println is the function name
• Parentheses () contain the arguments
• Multiple arguments are separated by commas

Practical Usage

Multiple Arguments

fun main() {
    println("Hello", "World", "from", "Ruchy");
}

Output:

Hello World from Ruchy

Variables and String Interpolation

Ruchy supports both string concatenation and f-string interpolation:

fun main() {
    let name = "Alice";

    // Multiple arguments (comma-separated)
    println("Hello,", name);

    // String concatenation with +
    println("Hello, " + name + "!");

    // F-string interpolation (modern, clean syntax)
    println(f"Hello, {name}!");
}

Output:

Hello, Alice
Hello, Alice!
Hello, Alice!

F-String Advantages:

• Cleaner syntax than concatenation
• Supports format specifiers: f"{pi:.2}" for 2 decimal places
• More readable for complex strings
• Zero performance overhead

Numbers and Other Types

fun main() {
    println("The answer is", 42);
    println("Pi is approximately", 3.14159);
    println("Is Ruchy awesome?", true);
}

Output:

The answer is 42
Pi is approximately 3.14159
Is Ruchy awesome? true

Common Pitfalls

Forgetting Quotes

// ❌ This won't work - intentional error example
// println(Hello, World!);
//

// Always use quotes for literal text.

fun main() {
    // ✅ Correct way:
    println("Hello, World!");
}

Mixing Quote Types

// ❌ Quotes don't match - intentional error example
// println("Hello, World!');
//

// Use either "..." or '...' but be consistent.

fun main() {
    // ✅ Correct way:
    println("Hello, World!");
}

Case Sensitivity

// ❌ Wrong capitalization - intentional error example
// PrintLn("Hello, World!");
//


fun main() {
    // ✅ Correct way:
    println("Hello, World!");
}

Generated Code Insight

Ever wonder what happens “under the hood” when you write Ruchy code? Let’s peek behind the curtain.

fun main() {
    println("Hello, World!");
}

fn main() {
    println!("Hello, World!");
}

The Bottom Line: Ruchy gives you Python-like simplicity with Rust-like performance. You’re not sacrificing speed for ease of use.

Try It Yourself

Time to get your hands dirty! Fire up the REPL and experiment:

$ ruchy repl
>>> # Start with your own greeting
>>> println("Hello, [YOUR NAME]!")
>>> 
>>> # Try multiple arguments
>>> println("My favorite number is", 42)
>>> 
>>> # Mix different types
>>> println("Learning Ruchy:", true, "Progress:", 100, "%")
>>>
>>> # Personal touch - make it yours!
>>> let my_language = "Ruchy" 
>>> let excitement_level = "maximum"
>>> println("I'm learning " + my_language + " with " + excitement_level + " enthusiasm!")

Your Challenge:

1. Personal Greeting: Create a greeting that includes your name, age, and why you’re learning Ruchy
2. Data Mix: Use println with at least 4 different data types in one call
3. String Concatenation: Use the + operator to create a personalized message

Example Output:

Hi! I'm Alex, 28 years old, learning Ruchy for data science
Mixing types: text 42 3.14 true null
My goal: I want to build fast applications with Ruchy!

The REPL is your playground - break things, experiment, learn!

Summary

• println(...) is your tool for displaying output
• String literals use double quotes: "text"
• Function calls use parentheses: function_name(arguments)
• Ruchy transpiles to clean, efficient Rust code
• The REPL is perfect for quick experiments

Now that you can make Ruchy speak, let’s learn about storing and manipulating information with variables and types.