Code Snippets

A handful of complete, runnable AHA! programs. Every snippet uses only features that exist today — save one to a .aha file and run it with cargo run --release -- --file <name>.aha.

Factorial

Recursion with an if/else expression:

fn factorial(n) {
    if n <= 1 {
        1
    } else {
        n * factorial(n - 1)
    }
}

print(factorial(5)); // 120

Fibonacci

Iterative Fibonacci with a while loop and reassignment:

fn fib(n) {
    let a = 0;
    let b = 1;
    let i = 0;
    while i < n {
        let next = a + b;
        a = b;
        b = next;
        i = i + 1;
    }
    a
}

print(fib(10)); // 55

Primality Test

Comparisons return Int 0/1, so the result of a check composes straight into control flow:

fn is_prime(n) {
    if n < 2 {
        return 0;
    }
    let i = 2;
    while i * i <= n {
        if n % i == 0 {
            return 0;
        }
        i = i + 1;
    }
    1
}

print(is_prime(7));  // 1
print(is_prime(12)); // 0

Multiplication Table

Nested for loops over integer ranges:

fn table(size) {
    for row 1..size {
        for col 1..size {
            print(row * col);
        }
    }
    0
}

table(4);

Sum of an Array

Arrays pair naturally with a ranged for loop:

let data = [4, 8, 15, 16, 23, 42];
let sum = 0;
for i in 0..6 {
    sum = sum + data[i];
}
print(sum); // 108

Counting with Mutual Recursion

Functions can call each other regardless of declaration order:

fn is_even(n) {
    n % 2 == 0
}

fn is_odd(n) {
    if is_even(n) { 0 } else { 1 }
}

let odds = 0;
for i in 0..10 {
    if is_odd(i) {
        odds = odds + 1;
    }
}
print(odds); // 5

String Building

Concatenation returns a fresh string; len() is O(1):

fn greet(name) {
    "Hello, " + name + "!"
}

let msg = greet("world");
print_str(msg);       // Hello, world!
print(len(msg));      // 13

Want the language reference behind these? See the Language Tour and Functions.