Booleans

A bool is true or false. Comparisons give one, and &&, || and ! combine them.

pub fn alive(hp: int, shielded: bool) -> bool {
    hp > 0 || shielded
}

pub fn exposed(hp: int, shielded: bool) -> bool {
    !shielded && hp < 10
}

// alive(0, true) == true
// exposed(5, false) == true

A condition is a bool

if and while take a bool and nothing else. A number, a string or an optional is not a condition, so write the comparison you mean.

pub fn broken(n: int) -> int { if n { 1 } else { 0 } }

// error: 1:35: expected bool, got int

pub fn fixed(n: int) -> int { if n != 0 { 1 } else { 0 } }

// fixed(3) == 1

A bool read out of an any needs .as_bool() first.

Bools and numbers

bool as int gives 1 or 0. The other direction does not exist: write n != 0.

pub fn count(a: bool, b: bool) -> int { (a as int) + (b as int) }

// count(true, true) == 2

&& and || stop at the first side that decides, as Operators shows.