function
none
none() -> option
The empty option — a missing value with no sentinel. Return it when there is nothing to give: no target, an empty slot, a lookup that missed. The caller distinguishes it from some with is_none / is_some, or supplies a default with unwrap_or.
Example
program Slots {
function held(slot: int) -> option {
if slot < 0 { return none() }
return some(slot)
}
test "none is empty" {
expect_eq(is_none(held(0 - 1)), true)
}
}