option.nula

// Nulang standard library — Option combinators.
// Import: `import stdlib::option`

/// The Option type: represents a value that may or may not be present.
pub type Option[T] = Some(T) | None

/// Unwrap an Option, returning the Some value.
/// Panics (via Test.assert) on None.
pub fn unwrap[T](opt: Option[T]) -> T {
    match opt {
        Some(x) => x,
        None => perform Test.assert(false, "called `unwrap` on a None value"),
    }
}

/// Returns true if the Option is Some.
pub fn is_some[T](opt: Option[T]) -> Bool {
    match opt {
        Some(_) => true,
        None => false,
    }
}

/// Returns true if the Option is None.
pub fn is_none[T](opt: Option[T]) -> Bool {
    match opt {
        Some(_) => false,
        None => true,
    }
}

/// Map a function over an Option.
pub fn map[T, U](opt: Option[T], f) -> Option[U] {
    match opt {
        Some(x) => Some(f(x)),
        None => None,
    }
}