2016 Update

Task/Y-combinator/Rust/y-combinator.rust

@@ -1,27 +1,24 @@
 use std::sync::Arc;
-use std::boxed::Box;
-use std::clone::Clone;
 
 //Arc<Box<Closure>>
-#[macro_export]
 macro_rules! abc {
     ($x:expr) => (Arc::new(Box::new($x)));
 }
 
 #[derive(Clone)]
-pub enum Mu<T> {
+enum Mu<T> {
     Roll(Arc<Box<Fn(Mu<T>)->T>>),
 }
 
-pub fn unroll<T>(Mu::Roll(f): Mu<T>) -> Arc<Box<Fn(Mu<T>)->T>> {f.clone()}
+fn unroll<T>(Mu::Roll(f): Mu<T>) -> Arc<Box<Fn(Mu<T>)->T>> {f.clone()}
 
-pub type Func<A, B> = Arc<Box<Fn(A)->B>>;
-pub type RecFunc<A, B> = Arc<Box<Fn(Func<A, B>) -> Func<A, B>>>;
+pub type Func<A> = Arc<Box<Fn(A)->A>>;
+pub type RecFunc<A> = Arc<Box<Fn(Func<A>) -> Func<A>>>;
 
-pub fn y<A, B>(f: RecFunc<A, B>) -> Func<A, B> {
-    let g:Arc<Box<Fn(Mu<Func<A, B>>)->Func<A, B>>> = abc!(move |x : Mu<Func<A, B>>| -> Func<A, B> {
+pub fn y<A: 'static>(f: RecFunc<A>) -> Func<A> {
+    let g: Arc<Box<Fn(Mu<Func<A>>)->Func<A>>> = abc!(move |x : Mu<Func<A>>| -> Func<A> {
         let f = f.clone();
-        abc!(move |a:A| -> B {
+        abc!(move |a:A| -> A {
             let f = f.clone();
             f(unroll(x.clone())(x.clone()))(a)
         })
@@ -29,16 +26,24 @@ pub fn y<A, B>(f: RecFunc<A, B>) -> Func<A, B> {
     g(Mu::Roll(g.clone()))
 }
 
-#[test]
-fn fib_test() {
-    let fib : RecFunc<i32, i32> = abc!(|f| abc!(move |x| if (x<2) { 1 } else { f(x-1) + f(x-2)}));
-    let b = y(fib)(10);
-    assert_eq!(b, 89);
+#[macro_export]
+macro_rules! y {
+    (|$name:ident| $fun:tt) => {
+        y(abc!(|$name| abc!($fun)))
+    }
 }
 
-#[test]
-fn fac_test() {
-    let fac : RecFunc<i32, i32> = abc!(|f| abc!(move |x| if (x==0) { 1 } else { f(x-1) * x }));
-    let c = y(fac)(10);
-    assert_eq!(c, 3628800);
+fn fac(n: u32) -> u32 {
+    let fn_: Func<u32> = y!(|f| (move |x| if x == 0 { 1 } else { f(x-1) * x }));
+    fn_(n)
+}
+
+fn fib(n: u32) -> u32 {
+    let fn_: Func<u32> = y!(|f| (move |x| if x < 2 { x } else { f(x-1) + f(x-2) }));
+    fn_(n)
+}
+
+fn main() {
+    println!("{}", fac(10));
+    println!("{}", fib(10))
 }