iterator: implement collect with FromIterator

This makes it take advantage of the size hint for pre-allocation.

Author: thestinger

src/libstd/iterator.rs

@@ -20,7 +20,7 @@ implementing the `Iterator` trait.
 #[allow(default_methods)]; // solid enough for the use case here
 
 use cmp;
-use iter::{FromIter, Times};
+use iter::Times;
 use num::{Zero, One};
 use option::{Option, Some, None};
 use ops::{Add, Mul};
@@ -240,7 +240,7 @@ pub trait IteratorUtil<A> {
     fn advance(&mut self, f: &fn(A) -> bool) -> bool;
 
     /// Loops through the entire iterator, collecting all of the elements into
-    /// a container implementing `FromIter`.
+    /// a container implementing `FromIterator`.
     ///
     /// # Example
     ///
@@ -249,7 +249,7 @@ pub trait IteratorUtil<A> {
     /// let b: ~[int] = a.iter().transform(|&x| x).collect();
     /// assert!(a == b);
     /// ~~~
-    fn collect<B: FromIter<A>>(&mut self) -> B;
+    fn collect<B: FromIterator<A, Self>>(&mut self) -> B;
 
     /// Loops through `n` iterations, returning the `n`th element of the
     /// iterator.
@@ -411,8 +411,8 @@ impl<A, T: Iterator<A>> IteratorUtil<A> for T {
     }
 
     #[inline]
-    fn collect<B: FromIter<A>>(&mut self) -> B {
-        FromIter::from_iter::<A, B>(|f| self.advance(f))
+    fn collect<B: FromIterator<A, T>>(&mut self) -> B {
+        FromIterator::from_iterator(self)
     }
 
     /// Return the `n`th item yielded by an iterator.

src/libstd/vec.rs

@@ -2500,6 +2500,17 @@ impl<T> FromIter<T> for ~[T]{
     }
 }
 
+#[cfg(stage0)]
+impl<A, T: Iterator<A>> FromIterator<A, T> for ~[A] {
+    pub fn from_iterator(iterator: &mut T) -> ~[A] {
+        let mut xs = ~[];
+        for iterator.advance |x| {
+            xs.push(x);
+        }
+        xs
+    }
+}
+
 #[cfg(not(stage0))]
 impl<A, T: Iterator<A>> FromIterator<A, T> for ~[A] {
     pub fn from_iterator(iterator: &mut T) -> ~[A] {