option

Optional values.

The Option type represents a value that may or may not be present.

Types

Option

Some('t)

None

Functions

is_none

fn(original: Option<'a>) -> Bool

Returns true if the option is None.

import core/option { Some, None }
test.assert(option.is_none(None));
test.assert(!option.is_none(Some(1)));

is_some

fn(original: Option<'a>) -> Bool

Returns true if the option contains a value.

import core/option { Some, None }
test.assert(option.is_some(Some(1)));
test.assert(!option.is_some(None));

map

fn(original: Option<'b>, map_fun: fn ('b) -> 'b / 't8) -> Option<'b> / 't8

Applies a function to the value inside a Some, or returns None.

import core/option { Some, None }
test.assert_eq(option.map(Some(3), fn(x) { x * 2 }), Some(6));
test.assert_eq(option.map(None, fn(x) { x * 2 }), None);

then

fn(condition: Bool, value: 'a) -> Option<'a>

Returns Some(value) if the condition is true, otherwise None.

import core/option { Some, None }
test.assert_eq(option.then(true, 42), Some(42));
test.assert_eq(option.then(false, 42), None);