While Loops

Demonstrates the while loop for repeated execution.

Example 012 of the basic Soma programs: a small, commented program that teaches one thing. Every output below was printed by soma 3.2.4 when this page was built.

How it is built

The cell Countdown has no face and no memory. Handlers: countdown (line 17) and power (line 33).

Generated from soma describe on this file.

The source

012_while_loop.cell

// ============================================================================
// 012 — While Loops
// ============================================================================
// Demonstrates the while loop for repeated execution.
//
// Run:   soma run 012_while_loop.cell countdown 5
// Expect:
//   5...
//   4...
//   3...
//   2...
//   1...
//   Liftoff!

cell Countdown {

    on countdown(n: Int) {
        let i = n

        // "while" repeats as long as the condition is true
        while i > 0 {
            print("{i}...")
            i = i - 1
        }

        print("Liftoff!")
        return "done"
    }

    // Another example: computing powers with a while loop
    // Run: soma run 012_while_loop.cell power 2 10
    // Expect: 2^10 = 1024
    on power(base: Int, exp: Int) {
        let result = 1
        let i = 0
        while i < exp {
            result = result * base
            i = i + 1
        }
        print("{base}^{exp} = {result}")
        return result
    }
}

What the toolchain says

$ soma check 012_while_loop.cell
✓ All checks passed.

$ soma run 012_while_loop.cell countdown 5
5...
4...
3...
2...
1...
Liftoff!
done