'Type for `|f| move |A| A.map(f)`
My previous QA
What is the type for |x| move |y| x + y?
Thanks to the provided answer, the following code works.
#![feature(type_alias_impl_trait)]
type Adder = impl Fn(isize) -> isize;
type Plus = fn(isize) -> Adder;
let plus: Plus = |x| move |y| x + y;
println!("{}", plus(9)(1)); //10
Based on this, now I try to re-define map Functor.
#![feature(type_alias_impl_trait)]
type Mapper<A, B> = impl Fn(Vec<A>) -> Vec<B>;
type Map = <A, B>(fn(fn(A) -> B) -> Mapper<A, B>);
let map:Map = |f| move |A| A.map(f);
let f = |a| a * 2;
let A = vec![1, 2, 3];
let B = map(f)(A);
However, the first line got an error: could not find defining uses, the second line, for <A, B> syntax error.
Is it possible to fix this?
Sources
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Source: Stack Overflow
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