09_loops.nula

// 09_loops.nula - Iteration: while and for loops
// Demonstrates: while, for-in, break with and without values,
//               loop-based algorithms using mutable state
//
// Run: nulang examples/09_loops.nula

// While loop: count down using a mutable array cell
let countdown = fn(n) {
    let st = [n]
    while st[0] > 0 {
        perform IO.print("  " + perform Int.to_string(st[0]))
        st[0] = st[0] - 1
    }
    perform IO.print("  Blast off!")
}
perform IO.print("Countdown from 5:")
countdown(5)

// While loop with break returning a value
let find_first_even = fn(xs) {
    let st = [0]
    while st[0] < 5 {
        if xs[st[0]] % 2 == 0 then break xs[st[0]] else unit
        st[0] = st[0] + 1
    }
}
let arr = [3, 7, 4, 9, 2]
let ev = find_first_even(arr)
perform IO.print("First even in [3,7,4,9,2]: " + perform Int.to_string(ev))

// For loop over an array
perform IO.print("Elements of [10,20,30,40,50]:")
for x in [10, 20, 30, 40, 50] {
    perform IO.print("  " + perform Int.to_string(x))
}

// For loop with break returning a value
let sum_until = fn(limit) {
    let st = [0]
    for x in [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] {
        let new_total = st[0] + x
        if new_total > limit then break st[0] else unit
        st[0] = new_total
    }
}
perform IO.print("Sum until > 12: " + perform Int.to_string(sum_until(12)))

// Nested loops
perform IO.print("Multiplication table (1-3):")
for a in [1, 2, 3] {
    let st = [1]
    while st[0] <= 3 {
        perform IO.print("  " + perform Int.to_string(a) + "x" + perform Int.to_string(st[0]) + "=" + perform Int.to_string(a * st[0]))
        st[0] = st[0] + 1
    }
}