Another update from ingydotnet^djgoku

Task/Fibonacci-sequence/Rust/fibonacci-sequence-1.rust

@@ -1,66 +1,30 @@
-// Works with 0.13.0-dev (f673e9841)
-fn fib<F>(n: i64, f: F) -> (i64, i64) where F: Fn(i64) {
-    if n < 0 {
-        // Let these variables be mutated, otherwise too slow
-        let mut n1:i64 = 0;
-        let mut n2:i64 = -1;
-        let mut i:i64 = 0;
-        let mut tmp:i64;
+#![feature(zero_one)]
+use std::num::One;
+use std::ops::Add;
 
-        while i > n {
-            f(n1);
-            tmp = n1-n2;
-            if tmp > 0 && n2 > 0 { //Detect overflow
-                println!("\nReached the limit of i64, halting");
-                return (n1, i);
-            }
-            n1 = n2;
-            n2 = tmp;
-            i -= 1;
-        }
-        (n1+n2, n)
-    } else if n > 0 {
-        // And these variables
-        let mut n1:i64 = 0;
-        let mut n2:i64 = 1;
-        let mut i:i64 = 0;
-        let mut tmp:i64;
+struct Fib<T> {
+    curr: T,
+    next: T,
+}
 
-        while i < n {
-            f(n1);
-            tmp = n1+n2;
-            if tmp < 0 { //Detect overflow
-                println!("\nReached the limit of i64, halting");
-                return (n1, i);
-            }
-            n1 = n2;
-            n2 = tmp;
-            i += 1;
-        }
-        (n2-n1, n)
-    } else {
-        f(0);
-        (0,1)
+impl<T> Fib<T> where T: One {
+    fn new() -> Self {
+        Fib {curr: T::one(), next: T::one()}
+    }
+}
+
+impl<T> Iterator for Fib<T> where T: Add<T, Output=T> + Copy {
+    type Item = T;
+    fn next(&mut self) -> Option<Self::Item>{
+        let new = self.curr + self.next;
+        self.curr = self.next;
+        self.next = new;
+        Some(self.curr)
     }
 }
 
 fn main() {
-    let args = std::os::args();
-    let default_n = 10i64;
-    let n = match args.len() {
-        1 => default_n,
-        _ => args[1].parse().unwrap_or(default_n)
-    };
-
-    /* Use the loop protocol to be able to do things
-     * with the sequence given, in this case, print them out.
-     * The loop itself returns a tuple with where it got to and
-     * what the number is.
-     */
-    let (result, n) = fib(n, |num| {
-        //print out the sequence
-        print!("{} ", num);
-    });
-
-    println!("\nThe {}th fibonacci number is: {}", n, result);
+    for i in Fib::<u64>::new() {
+        println!("{}", i);
+    }
 }