Data commit

Task/Happy-numbers/Rust/happy-numbers.rust

@@ -0,0 +1,36 @@
+#![feature(core)]
+
+fn sumsqd(mut n: i32) -> i32 {
+    let mut sq = 0;
+    while n > 0 {
+        let d = n % 10;
+        sq += d*d;
+        n /= 10
+    }
+    sq
+}
+
+use std::num::Int;
+fn cycle<T: Int>(a: T, f: fn(T) -> T) -> T {
+    let mut t = a;
+    let mut h = f(a);
+
+    while t != h {
+        t = f(t);
+        h = f(f(h))
+    }
+    t
+}
+
+fn ishappy(n: i32) -> bool {
+    cycle(n, sumsqd) == 1
+}
+
+fn main() {
+    let happy = std::iter::count(1, 1)
+                    .filter(|&n| ishappy(n))
+                    .take(8)
+                    .collect::<Vec<i32>>();
+
+    println!("{:?}", happy)
+}