75 lines
1.7 KiB
Rust
75 lines
1.7 KiB
Rust
use crate::func::*;
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struct LazyClass;
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impl WeakFunctor for LazyClass {
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type F<'a, A> = Box<dyn 'a + FnOnce() -> A>;
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}
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impl Functor for LazyClass {
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fn fmap<'a, A: 'a, B: 'a, F: 'a + FnOnce(A) -> B>(f: F, fa: Self::F<'a, A>) -> Self::F<'a, B> {
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Box::new(|| f(fa()))
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}
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fn replace<'a, A: 'a, B: 'a>(fa: Self::F<'a, A>, b: B) -> Self::F<'a, B> {
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drop(fa);
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Box::new(|| b)
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}
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fn void<'a, A: 'a>(fa: Self::F<'a, A>) -> Self::F<'a, ()> {
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drop(fa);
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Box::new(|| ())
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}
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}
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impl ApplicativeSeq for LazyClass {
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fn seq<'a, A: 'a, B: 'a, F: 'a + FnOnce(A) -> B>(
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ff: Self::F<'a, F>,
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fa: Self::F<'a, A>,
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) -> Self::F<'a, B> {
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Box::new(|| ff()(fa()))
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}
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}
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impl ApplicativeLA2 for LazyClass {
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fn la2<'a, A: 'a, B: 'a, C: 'a, F: 'a + FnOnce(A, B) -> C>(
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f: F,
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fa: Self::F<'a, A>,
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fb: Self::F<'a, B>,
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) -> Self::F<'a, C> {
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Box::new(|| f(fa(), fb()))
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}
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}
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impl Applicative for LazyClass {
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fn pure<'a, A: 'a>(a: A) -> Self::F<'a, A> {
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Box::new(|| a)
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}
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fn discard_first<'a, A: 'a, B: 'a>(fa: Self::F<'a, A>, fb: Self::F<'a, B>) -> Self::F<'a, B> {
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drop(fa);
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fb
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}
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fn discard_second<'a, A: 'a, B: 'a>(fa: Self::F<'a, A>, fb: Self::F<'a, B>) -> Self::F<'a, A> {
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drop(fb);
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fa
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}
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}
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impl Monad for LazyClass {
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fn bind<'a, A: 'a, B: 'a, F: 'a + FnOnce(A) -> Self::F<'a, B>>(
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fa: Self::F<'a, A>,
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f: F,
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) -> Self::F<'a, B> {
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Box::new(|| f(fa())())
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}
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fn join<'a, A: 'a>(ffa: Self::F<'a, Self::F<'a, A>>) -> Self::F<'a, A>
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where
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Self::F<'a, A>: 'a,
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{
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Box::new(|| ffa()())
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}
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}
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