Hello, World: Your First Program

Every programmer's tradition begins with one tiny program: printing the words "Hello, World!". Let's get started.

Your First Program

Create a file named halo.aha with the contents:

print_str("Hello, World!");

Run it:

cargo run --release -- --file halo.aha

Output:

Hello, World!

Congratulations — you've just written and run your first program! 🎉

Anatomy of One Line

print_str("Hello, World!");

Part	Meaning
`print_str`	Built-in function (builtin) for printing a string
`("Hello, World!")`	Argument — the text you want to print, enclosed in double quotes
`;`	Marks the end of a statement

In AHA! Lang, every statement ends with a semicolon ;.

Printing Numbers

To print a number, use print:

print(42);
print(7 + 5);

Output:

42
12

Note: print prints numbers, print_str prints text. Mixing them — like print("halo") — will be rejected by the compiler at compile time, because of the wrong type. This is the type discipline mentioned in the first lesson.

Comments: Notes for Humans

Code needs explanations too. Comments are written with // (single line) or /* ... */ (multiple lines), and are ignored by the compiler:

// this is a single-line comment
print(1); // it can also be at the end of a line

/*
   This is a
   multi-line comment.
*/
print(2);

Comments are the best way to explain why you wrote something — not what the code does.

Printing Multiple Lines

Use the escape \n for a new line:

print_str("Baris satu\nBaris dua");

Output:

Baris satu
Baris dua

Exercises

Change the program above to print your name.
Print three lines: your name, a hobby, and an aspiration — using three print_str calls.
Print the result of 2 + 2 with print.

On to Variables and Data Types?