map_poly_simple.rs

use std::boxed::Box;

enum List<T> {
    Null,
    Cons(T, Box<List<T>>),
}


fn map_noref<A, B, F>(f: &F, lst: List<A>) -> List<B>
    where F: Fn(A) -> B
{
    match (lst) {
        List::Null => List::Null,
        List::Cons(h, t) => {
            let newHead = f(h);
            let newTail = map_noref(f, *t);
            List::Cons(newHead, Box::new(newTail))
        }
    }
}

fn map_ref<A, B, F>(f: &F, lst: &List<A>) -> List<B>
    where F: Fn(&A) -> B
{
    match (*lst) {
        List::Null => List::Null,
        List::Cons(ref h, ref t) => {
            let newHead = f(h);
            let newTail = map_ref(f, t);
            List::Cons(newHead, Box::new(newTail))
        }
    }
}




fn main() {}