getFirstMonoid<T> static method
Build an instance of Monoid in which the empty
value is None and the
combine
function is based on the first Option
if it is Some, otherwise the second.
Implementation
static Monoid<Option<T>> getFirstMonoid<T>() =>
Monoid.instance(const Option.none(), (a1, a2) => a1.isNone() ? a2 : a1);