Control Flow

if, else if, and else are working control-flow constructs, together with break, continue, and return.

fn sign(value: i32): i32 {
    if (value < 0) {
        -1
    } else {
        1
    }
}

Loops

for is the loop keyword. Three forms work today: the infinite loop for { }, the conditional loop for (cond) { }, and the 3-clause loop for (init; cond; step) { } with semicolon separators. init and step are both optional, and continue still runs the step before the next test.

fn sum(n: i32): i32 {
    var total: i32 = 0;
    for (var i: i32 = 0; i < n; i = i + 1) {
        total += i;
    }
    total
}

while still compiles, but it emits the deprecation warning W1008 telling you to write for (cond) { } instead. The iterator form for (x in xs) is not implemented and reports a parse error.

Pattern matching

when matches a value against comma-separated arms written (pattern) ~> body. match is a synonym for the same construct. Equality, boolean, and range patterns lower through HIR to code generation.

fn classify(x: i32): i32 {
    when (x) {
        (0) ~> 100,
        (1..3) ~> 200,
        (_) ~> 300,
    }
}

(_) is the default arm and must be written last. A when used for its value without a default is rejected as non-exhaustive.

Not yet available

marker and jump work as a block-style go-to inside flow fn; dock is still a parse error. Consult the Control Flow reference for the intended semantics and Implementation Status for the current boundary.