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January 4, 2023 13:10
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pub trait Function {}
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| pub trait Function<TMarker> { | |
| type Args; | |
| type Result; | |
| fn exec(&self, args: Self::Args) -> Self::Result; | |
| } | |
| // TODO: Duplicate all the impls for `FnOnce` and `FnMut` | |
| // TODO: Support up to 12 args per functions. | |
| pub enum TMarker {} | |
| impl<R, TFunc: Fn() -> R> Function<TMarker> for TFunc { | |
| type Args = (); | |
| type Result = R; | |
| fn exec(&self, _: Self::Args) -> Self::Result { | |
| (self)() | |
| } | |
| } | |
| impl<T, R, TFunc: Fn(T) -> R> Function<(T, R)> for TFunc { | |
| type Args = T; | |
| type Result = R; | |
| fn exec(&self, args: Self::Args) -> Self::Result { | |
| (self)(args) | |
| } | |
| } | |
| impl<T, T1, R, TFunc: Fn(T, T1) -> R> Function<(T, T1, R)> for TFunc { | |
| type Args = (T, T1); | |
| type Result = R; | |
| fn exec(&self, args: Self::Args) -> Self::Result { | |
| (self)(args.0, args.1) | |
| } | |
| } | |
| impl<T, T1, T2, R, TFunc: Fn(T, T1, T2) -> R> Function<(T, T1, T2, R)> for TFunc { | |
| type Args = (T, T1, T2); | |
| type Result = R; | |
| fn exec(&self, args: Self::Args) -> Self::Result { | |
| (self)(args.0, args.1, args.2) | |
| } | |
| } | |
| fn joiner<A, TMarker1, B, TMarker2>( | |
| a: A, | |
| b: B, | |
| ) -> impl Function< | |
| ( | |
| <A as Function<TMarker1>>::Args, | |
| <B as Function<TMarker2>>::Result, | |
| ), | |
| Args = <A as Function<TMarker1>>::Args, | |
| Result = <B as Function<TMarker2>>::Result, | |
| > | |
| where | |
| A: Function<TMarker1>, | |
| B: Function<TMarker2, Args = A::Result>, | |
| { | |
| move |args: A::Args| b.exec(a.exec(args)) | |
| } | |
| fn from_into_string(s: impl Into<String>) -> i32 { | |
| s.into().parse::<i32>().unwrap() | |
| } | |
| pub trait SpecialType {} | |
| #[derive(Clone)] | |
| pub struct Demo; | |
| impl SpecialType for Demo {} | |
| fn only_special_types(_s: impl SpecialType) -> &'static str { | |
| "my precious" | |
| } | |
| fn main() { | |
| let a = |a: i32| a.to_string(); | |
| let b = |a: String| a.parse::<i32>().unwrap(); | |
| // i32 to String -> String to i32 | |
| let c = joiner(a, b); | |
| println!("{}", c.exec(42)); | |
| // i32 to String -> `impl Into<String>` to i32 | |
| let c = joiner(a, from_into_string); | |
| println!("{}", c.exec(42)); | |
| let a = Demo {}; // Will compile | |
| // let a = "this is not the special type"; // Will not compile because it doesn't satisfy the trait bound on `only_special_types` | |
| let c = joiner(move || a.clone(), only_special_types); | |
| println!("{}", c.exec(())); | |
| } |
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