2016 Update

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

@@ -1,30 +1,12 @@
-#![feature(zero_one)]
-use std::num::One;
-use std::ops::Add;
-
-struct Fib<T> {
-    curr: T,
-    next: T,
-}
-
-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)
-    }
-}
-
+use std::mem;
 fn main() {
-    for i in Fib::<u64>::new() {
-        println!("{}", i);
+    let mut prev = 0;
+    // Rust needs this type hint for the checked_add method
+    let mut curr = 1usize;
+
+    while let Some(n) = curr.checked_add(prev) {
+        prev = curr;
+        curr = n;
+        println!("{}", n);
     }
 }

Task/Fibonacci-sequence/Rust/fibonacci-sequence-2.rust

@@ -1,16 +1,12 @@
+use std::mem;
 fn main() {
-    fn fib(n: i32) -> i32 {
-        fn _fib(n: i32, a: i32, b: i32) -> i32 {
-            match (n, a, b) {
-                (0, _, _) => a,
-                _         => _fib(n-1, a+b, a)
-            }
-        }
+    fibonacci(0,1);
+}
 
-        _fib(n, 0, 1)
-    }
-
-    for n in 0..20 {
-        println!("{}", fib(n));
+fn fibonacci(mut prev: usize, mut curr: usize) {
+    mem::swap(&mut prev, &mut curr);
+    if let Some(n) = curr.checked_add(prev) {
+        println!("{}", n);
+        fibonacci(prev, n);
     }
 }

Task/Fibonacci-sequence/Rust/fibonacci-sequence-3.rust

@@ -0,0 +1,14 @@
+#![feature(conservative_impl_trait)]
+
+fn main() {
+    for num in fibonacci_gen(10) {
+        println!("{}", num);
+    }
+}
+
+fn fibonacci_gen(terms: i32) -> impl Iterator<Item=f64> {
+    let sqrt_5 = 5.0f64.sqrt();
+    let p  = (1.0 +sqrt_5) / 2.0;
+    let q = 1.0/p;
+    (1..terms).map(move |n| ((p.powi(n) + q.powi(n)) / sqrt_5 + 0.5).floor())
+}

Task/Fibonacci-sequence/Rust/fibonacci-sequence-4.rust

@@ -0,0 +1,29 @@
+use std::mem;
+
+struct Fib {
+    prev: usize,
+    curr: usize,
+}
+
+impl Fib {
+    fn new() -> Self {
+        Fib {prev: 0, curr: 1}
+    }
+}
+
+impl Iterator for Fib {
+    type Item = usize;
+    fn next(&mut self) -> Option<Self::Item>{
+        mem::swap(&mut self.curr, &mut self.prev);
+        self.curr.checked_add(self.prev).map(|n| {
+            self.curr = n;
+            n
+        })
+    }
+}
+
+fn main() {
+    for num in Fib::new() {
+        println!("{}", num);
+    }
+}