module ListMapRev2;

// The usual list rev_map function.
def List<A> rmap<A>(f)(List<A> l, List<A> acc) =
    case l {
    Nil => acc;
    Cons(x,xs) => rmap(xs, Cons(f(x),acc));
};

def List<A> map_rev<A>(f)(List<A> l) = rmal(l,Nil);


def List<A> rmap1<A>(f1,f2)(List<A> l, List<A> acc) =
    case l {
    Nil => acc;
    Cons(x,xs) => rmap2(f1,f2)(xs, Cons(f1(x), acc));
};

def List<A> rmap2<A>(f1,f2)(List<A> l, List<A> acc) =
    case l {
    Nil => acc;
    Cons(x,xs) => rmap1(f1,f2)(xs, Cons(f2(x),acc));
};


// Iteratively apply two functional arguments.
def List<A> map_rev2(f1, f2)(List<A> l) = rmap1(l, Nil);

def List<A> start(f1, f2)(List<A> l) = map_rev(f1,f2)(l);

{

}