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use crate::traits::Applicative;

impl<'a, A> Applicative<'a, A> for Option<A>
where
    A: 'a,
{
    type PureT<T> = T where T: 'a ;

    fn pure(a: Self::PureT<A>) -> Self::Type<Self::PureT<A>> {
        Some(a)
    }

    fn app<F, B>(self, f: Self::Type<F>) -> Self::Type<B>
    where
        F: Fn(A) -> B,
    {
        f.and_then(|f| self.map(f))
    }
}