if

Runs a block when a bool condition is true.

The condition needs no parentheses and the body always takes braces. Chain alternatives with else if and else. if let Pattern = value { … } runs the block when the value matches the pattern, binding its names.

fn sign(int n) -> int {
    if n < 0 {
        return -1;
    } else if n == 0 {
        return 0;
    } else {
        return 1;
    }
}

fn main() {
    let found = Option::Some(3);
    if let Option::Some(v) = found {
        let doubled = v * 2;
    }
}

See also#

• bool
• fn: Declares a function, a method, or (written in an expression) an anonymous function.
• let: Declares a mutable local variable.
• const: Declares a binding that cannot be reassigned: a local, a module constant, or a class field that is set only by new.
• static: Declares a module-level or class-level slot shared by the whole program, or a method without self.
• readonly: A read-only view of a value: nothing reachable through it can be changed.
• else: Introduces the branch of an if that runs when its condition is false (or its pattern does not match).
• while: Repeats a block while a bool condition is true.