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This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters. Learn more about bidirectional Unicode charactersOriginal file line number Diff line number Diff line change @@ -1,73 +1,83 @@ use std::marker::PhantomData; trait Family<'a> { type Member<T: 'a>: Mirror<'a, T, Family = Self>; } trait Mirror<'a, T> { type Family: Family<'a>; fn as_member(self) -> <Self::Family as Family<'a>>::Member<T>; } trait Functor<'a>: Family<'a> { fn fmap<A: 'a, B: 'a, F: FnMut(A) -> B + 'a>( fa: <Self as Family<'a>>::Member<A>, f: F, ) -> <Self as Family<'a>>::Member<B>; } trait FunctorSyntax<'a, A: 'a, Fam: Functor<'a>>: Mirror<'a, A, Family = Fam> + Sized { fn fmap<B, F: FnMut(A) -> B + 'a>( self, f: F, ) -> <Fam as Family<'a>>::Member<B> { <Fam as Functor>::fmap(self.as_member(), f) } } impl<'a, A: 'a, F: Functor<'a>, T: Mirror<'a, A, Family = F>> FunctorSyntax<'a, A, F> for T { } trait Applicative<'a>: Functor<'a> { fn pure<A: 'a>(a: A) -> <Self as Family<'a>>::Member<A>; fn zip<A: 'a, B: 'a>( fa: <Self as Family<'a>>::Member<A>, fb: <Self as Family<'a>>::Member<B>, ) -> <Self as Family<'a>>::Member<(A, B)>; } fn pure<'a, F: Applicative<'a>, A: 'a>(a: A) -> F::Member<A> { <F as Applicative>::pure(a) } trait ApplicativeSyntax<'a, A: 'a, Fam: Applicative<'a>>: Mirror<'a, A, Family = Fam> + Sized { fn zip<B: 'a>( self, fb: <Fam as Family<'a>>::Member<B>, ) -> <Fam as Family<'a>>::Member<(A, B)> { <Fam as Applicative>::zip(self.as_member(), fb) } } impl<'a, A: 'a, F: Applicative<'a>, T: Mirror<'a, A, Family = F>> ApplicativeSyntax<'a, A, F> for T { } // option struct OptionFamily; impl<'a> Family<'a> for OptionFamily { type Member<T: 'a> = Option<T>; } impl<'a, A: 'a> Mirror<'a, A> for Option<A> { type Family = OptionFamily; fn as_member(self) -> Option<A> { self } } impl<'a> Functor<'a> for OptionFamily { fn fmap<A, B, F: FnMut(A) -> B>(fa: Option<A>, f: F) -> Option<B> { fa.map(f) } } impl<'a> Applicative<'a> for OptionFamily { fn pure<A>(a: A) -> Option<A> { Some(a) } @@ -80,8 +90,106 @@ impl Applicative for OptionFamily { } } // result struct ResultFamily<'a, E: 'a> { phantom: PhantomData<&'a E>, } impl<'a, E: 'a> Family<'a> for ResultFamily<'a, E> { type Member<T: 'a> = Result<T, E>; } impl<'a, A: 'a, E: 'a> Mirror<'a, A> for Result<A, E> { type Family = ResultFamily<'a, E>; fn as_member(self) -> <Self::Family as Family<'a>>::Member<A> { self } } impl<'a, E: 'a> Functor<'a> for ResultFamily<'a, E> { fn fmap<A, B, F: FnMut(A) -> B>(fa: Result<A, E>, f: F) -> Result<B, E> { fa.map(f) } } impl<'a, E: 'a> Applicative<'a> for ResultFamily<'a, E> { fn pure<A>(a: A) -> Result<A, E> { Ok(a) } fn zip<A, B>(fa: Result<A, E>, fb: Result<B, E>) -> Result<(A, B), E> { fa.and_then(|a| fb.map(|b| (a, b))) } } // iterator struct IteratorWrap<'a, T>(Box<dyn Iterator<Item = T> + 'a>); trait IteratorSyntax<'a, T: Sized>: Iterator<Item = T> + Sized + 'a { fn wrap(self) -> IteratorWrap<'a, T> { IteratorWrap(Box::new(self)) } } impl<'a, T, I: Iterator<Item = T> + 'a> IteratorSyntax<'a, T> for I {} impl<'a, T> Iterator for IteratorWrap<'a, T> { type Item = T; fn next(&mut self) -> Option<Self::Item> { self.0.next() } } struct IteratorWrapFamily; impl<'a> Family<'a> for IteratorWrapFamily { type Member<T: 'a> = IteratorWrap<'a, T>; } impl<'a, T: 'a> Mirror<'a, T> for IteratorWrap<'a, T> { type Family = IteratorWrapFamily; fn as_member(self) -> <Self::Family as Family<'a>>::Member<T> { self } } impl<'a> Functor<'a> for IteratorWrapFamily { fn fmap<A: 'a, B, F: FnMut(A) -> B + 'a>( fa: IteratorWrap<'a, A>, f: F, ) -> IteratorWrap<'a, B> { IteratorWrap(Box::new(fa.0.into_iter().map(f).into_iter())) } } impl<'a> Applicative<'a> for IteratorWrapFamily { fn pure<A: 'a>(a: A) -> IteratorWrap<'a, A> { vec![a].into_iter().wrap() } fn zip<A: 'a, B: 'a>( fa: IteratorWrap<A>, fb: IteratorWrap<B>, ) -> IteratorWrap<'a, (A, B)> { let mut result = Vec::new(); let mut fa = fa; let mut fb = fb; while let (Some(a), Some(b)) = (fa.next(), fb.next()) { result.push((a, b)); } result.into_iter().wrap() } } // usage fn use_applicative<'a, A, F: Applicative<'a>>(a: A, b: A) -> F::Member<(A, A)> { let fa = pure::<F, _>(a); let fb = pure::<F, _>(b); fa.zip(fb) } fn foo() -> Option<(i32, i32)> { let a = Some(3); let b = a.fmap(|x| (x + 1, x)); b } fn use_iterator() -> IteratorWrap<'static, i32> { let v = vec![1]; v.into_iter().wrap().fmap(|x| x + 1).fmap(|x| x + 1) } -
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This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters. Learn more about bidirectional Unicode charactersOriginal file line number Diff line number Diff line change @@ -0,0 +1,87 @@ trait Family { type Member<T>: Mirror<T, Family = Self>; } trait Mirror<T> { type Family: Family; fn as_member(self) -> <Self::Family as Family>::Member<T>; } trait Functor: Family { fn fmap<A, B, F: FnMut(A) -> B>( fa: <Self as Family>::Member<A>, f: F, ) -> <Self as Family>::Member<B>; } trait FunctorSyntax<A, Fam: Functor>: Mirror<A, Family = Fam> + Sized { fn fmap<B, F: FnMut(A) -> B>(self, f: F) -> <Fam as Family>::Member<B> { <Fam as Functor>::fmap(self.as_member(), f) } } impl<A, F: Functor, T: Mirror<A, Family = F>> FunctorSyntax<A, F> for T {} trait Applicative: Functor { fn pure<A>(a: A) -> <Self as Family>::Member<A>; fn zip<A, B>( fa: <Self as Family>::Member<A>, fb: <Self as Family>::Member<B>, ) -> <Self as Family>::Member<(A, B)>; } fn pure<F: Applicative, A>(a: A) -> F::Member<A> { <F as Applicative>::pure(a) } trait ApplicativeSyntax<A, Fam: Applicative>: Mirror<A, Family = Fam> + Sized { fn zip<B>( self, fb: <Fam as Family>::Member<B>, ) -> <Fam as Family>::Member<(A, B)> { <Fam as Applicative>::zip(self.as_member(), fb) } } impl<A, F: Applicative, T: Mirror<A, Family = F>> ApplicativeSyntax<A, F> for T { } // usage struct OptionFamily; impl Family for OptionFamily { type Member<T> = Option<T>; } impl<A> Mirror<A> for Option<A> { type Family = OptionFamily; fn as_member(self) -> Option<A> { self } } impl Functor for OptionFamily { fn fmap<A, B, F: FnMut(A) -> B>(fa: Option<A>, f: F) -> Option<B> { fa.map(f) } } impl Applicative for OptionFamily { fn pure<A>(a: A) -> Option<A> { Some(a) } fn zip<A, B>(fa: Option<A>, fb: Option<B>) -> Option<(A, B)> { match (fa, fb) { (Some(a), Some(b)) => Some((a, b)), _ => None, } } } fn use_applicative<F: Applicative>(i: i32) -> F::Member<(i32, i32)> { let fa = pure::<F, _>(i); let fb = pure::<F, _>(i); fa.fmap(|x| x + 1).zip(fb) }