rhaj/rhai_engine/rhaibook/language/while.md

While Loop

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while loops follow C syntax.

Like C, continue can be used to skip to the next iteration, by-passing all following statements; break can be used to break out of the loop unconditionally.

`while` loops can be disabled via [`Engine::set_allow_looping`][options].

let x = 10;

while x > 0 {
    x -= 1;
    if x < 6 { continue; }  // skip to the next iteration
    print(x);
    if x == 5 { break; }    // break out of while loop
}

While Expression

Like Rust, while statements can also be used as expressions.

The break statement takes an optional expression that provides the return value.

The default return value of a while expression is [()].

Loop expressions can be disabled via [`Engine::set_allow_loop_expressions`][options].

let x = 0;

// 'while' can be used just like an expression
let result = while x < 100 {
    if is_magic_number(x) {
        // if the 'while' loop breaks here, return a specific value
        break get_magic_result(x);
    }

    x += 1;

    // ... if the 'while' loop exits here, the return value is ()
};

if result == () {
    print("Magic number not found!");
} else {
    print(`Magic result = ${result}!`);
}