Break, Continue, and Labels

Labeled: <Label> ':' <Loop | While | For | Block>;
Continue: 'continue' <Label>?;
Break: 'break' <Label>? <Expression>?;

Muse does not have a "go to" capability, but it offers several expressions that can jump to well-defined execution points: continue and break.

The well-defined execution points are:

• A loop's next iteration
• The first instruction after a loop body
• A labeled block or loop

Labels

A label is the @ character followed by an identifier, e.g., @label. Labels can be applied to blocks or loops to allow controlled execution flow in nested code.

var total = 0;
@outer: for x in [1, 2, 3] {
    for y in [1, 2, 3] {
        if x == y {
            continue @outer;
        };

        # Only executed for [(2, 1), (3,1), (3, 2)]
        total = total + x * y
    };
};
let 11 = total;

Continue

The continue expression takes an optional label. If no label is provided, execution jumps to the location to begin the next iteration of the loop containing the code. If no loop is found, a compilation error will occur.

If a label is provided, the label must belong to a loop. If not, a compilation error will occur.

Break

The break expression takes an optional label and an optional expression. If no label is provided, execution jumps to the location after the current loop exits. If no loop is found, a compilation error will occur.

If a label is provided, execution will jump to the the next instruction after the block or loop identified by that label. The result of the block or loop will be the optional expression or nil.