Rust-map-test.rs

use std::rc::Rc;

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




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


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

fn add_n(n : i32) -> Rc<Fn(i32) -> i32 + 'static>  {
    Rc::new(move |x| n + x)
}


fn map_curried<A,B,F, R>(f : Rc<F>) -> Box<Fn(Rc<List<A>>) -> Rc<List<B>> + 'static>
    where F: Fn(Rc<A>) -> Rc<B> + 'static,
          
{
    Box::new( move |lst: Rc<List<A>>| map_uncurried(f.clone(),lst.clone()))
}



fn main() {

   let square = map_curried(Rc::new(|x: i32| x * 2));

    println!("Hello, world!");
}