use crate::hkt::HKT;
pub trait Functor<A, B>: HKT<A, B> {
fn fmap<F>(self, f: F) -> <Self as HKT<A, B>>::Target
where
F: FnOnce(A) -> B;
}
impl<A, B> Functor<A, B> for Option<A> {
fn fmap<F>(self, f: F) -> Self::Target
where
F: FnOnce(A) -> B,
{
self.map(f)
}
}