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diff --git a/src/libstd/iter.rs b/src/libstd/iter.rs
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+// Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+/*! Composable internal iterators
+
+Internal iterators are functions implementing the protocol used by the `for` loop.
+
+An internal iterator takes `fn(...) -> bool` as a parameter, with returning `false` used to signal
+breaking out of iteration. The adaptors in the module work with any such iterator, not just ones
+tied to specific traits. For example:
+
+~~~~
+println(iter::to_vec(|f| uint::range(0, 20, f)).to_str());
+~~~~
+
+An external iterator object implementing the interface in the `iterator` module can be used as an
+internal iterator by calling the `advance` method. For example:
+
+~~~~
+use core::iterator::*;
+
+let xs = [0u, 1, 2, 3, 4, 5];
+let ys = [30, 40, 50, 60];
+let mut it = xs.iter().chain(ys.iter());
+for it.advance |&x: &uint| {
+    println(x.to_str());
+}
+~~~~
+
+Internal iterators provide a subset of the functionality of an external iterator. It's not possible
+to interleave them to implement algorithms like `zip`, `union` and `merge`. However, they're often
+much easier to implement.
+
+*/
+
+use cmp::Ord;
+use option::{Option, Some, None};
+use vec::OwnedVector;
+use num::{One, Zero};
+use ops::{Add, Mul};
+
+pub trait Times {
+    fn times(&self, it: &fn() -> bool) -> bool;
+}
+
+/**
+ * Transform an internal iterator into an owned vector.
+ *
+ * # Example:
+ *
+ * ~~~
+ * let xs = ~[1, 2, 3];
+ * let ys = do iter::to_vec |f| { xs.each(|x| f(*x)) };
+ * assert_eq!(xs, ys);
+ * ~~~
+ */
+#[inline(always)]
+pub fn to_vec<T>(iter: &fn(f: &fn(T) -> bool) -> bool) -> ~[T] {
+    let mut v = ~[];
+    for iter |x| { v.push(x) }
+    v
+}
+
+/**
+ * Return true if `predicate` is true for any values yielded by an internal iterator.
+ *
+ * Example:
+ *
+ * ~~~~
+ * let xs = ~[1u, 2, 3, 4, 5];
+ * assert!(any(|&x: &uint| x > 2, |f| xs.each(f)));
+ * assert!(!any(|&x: &uint| x > 5, |f| xs.each(f)));
+ * ~~~~
+ */
+#[inline(always)]
+pub fn any<T>(predicate: &fn(T) -> bool,
+              iter: &fn(f: &fn(T) -> bool) -> bool) -> bool {
+    for iter |x| {
+        if predicate(x) {
+            return true;
+        }
+    }
+    return false;
+}
+
+/**
+ * Return true if `predicate` is true for all values yielded by an internal iterator.
+ *
+ * # Example:
+ *
+ * ~~~~
+ * assert!(all(|&x: &uint| x < 6, |f| uint::range(1, 6, f)));
+ * assert!(!all(|&x: &uint| x < 5, |f| uint::range(1, 6, f)));
+ * ~~~~
+ */
+#[inline(always)]
+pub fn all<T>(predicate: &fn(T) -> bool,
+              iter: &fn(f: &fn(T) -> bool) -> bool) -> bool {
+    // If we ever break, iter will return false, so this will only return true
+    // if predicate returns true for everything.
+    iter(|x| predicate(x))
+}
+
+/**
+ * Return the first element where `predicate` returns `true`. Return `None` if no element is found.
+ *
+ * # Example:
+ *
+ * ~~~~
+ * let xs = ~[1u, 2, 3, 4, 5, 6];
+ * assert_eq!(*find(|& &x: & &uint| x > 3, |f| xs.each(f)).unwrap(), 4);
+ * ~~~~
+ */
+#[inline(always)]
+pub fn find<T>(predicate: &fn(&T) -> bool,
+               iter: &fn(f: &fn(T) -> bool) -> bool) -> Option<T> {
+    for iter |x| {
+        if predicate(&x) {
+            return Some(x);
+        }
+    }
+    None
+}
+
+/**
+ * Return the largest item yielded by an iterator. Return `None` if the iterator is empty.
+ *
+ * # Example:
+ *
+ * ~~~~
+ * let xs = ~[8, 2, 3, 1, -5, 9, 11, 15];
+ * assert_eq!(max(|f| xs.each(f)).unwrap(), &15);
+ * ~~~~
+ */
+#[inline]
+pub fn max<T: Ord>(iter: &fn(f: &fn(T) -> bool) -> bool) -> Option<T> {
+    let mut result = None;
+    for iter |x| {
+        match result {
+            Some(ref mut y) => {
+                if x > *y {
+                    *y = x;
+                }
+            }
+            None => result = Some(x)
+        }
+    }
+    result
+}
+
+/**
+ * Return the smallest item yielded by an iterator. Return `None` if the iterator is empty.
+ *
+ * # Example:
+ *
+ * ~~~~
+ * let xs = ~[8, 2, 3, 1, -5, 9, 11, 15];
+ * assert_eq!(max(|f| xs.each(f)).unwrap(), &-5);
+ * ~~~~
+ */
+#[inline]
+pub fn min<T: Ord>(iter: &fn(f: &fn(T) -> bool) -> bool) -> Option<T> {
+    let mut result = None;
+    for iter |x| {
+        match result {
+            Some(ref mut y) => {
+                if x < *y {
+                    *y = x;
+                }
+            }
+            None => result = Some(x)
+        }
+    }
+    result
+}
+
+/**
+ * Reduce an iterator to an accumulated value.
+ *
+ * # Example:
+ *
+ * ~~~~
+ * assert_eq!(fold(0i, |f| int::range(1, 5, f), |a, x| *a += x), 10);
+ * ~~~~
+ */
+#[inline]
+pub fn fold<T, U>(start: T, iter: &fn(f: &fn(U) -> bool) -> bool, f: &fn(&mut T, U)) -> T {
+    let mut result = start;
+    for iter |x| {
+        f(&mut result, x);
+    }
+    result
+}
+
+/**
+ * Reduce an iterator to an accumulated value.
+ *
+ * `fold_ref` is usable in some generic functions where `fold` is too lenient to type-check, but it
+ * forces the iterator to yield borrowed pointers.
+ *
+ * # Example:
+ *
+ * ~~~~
+ * fn product<T: One + Mul<T, T>>(iter: &fn(f: &fn(&T) -> bool) -> bool) -> T {
+ *     fold_ref(One::one::<T>(), iter, |a, x| *a = a.mul(x))
+ * }
+ * ~~~~
+ */
+#[inline]
+pub fn fold_ref<T, U>(start: T, iter: &fn(f: &fn(&U) -> bool) -> bool, f: &fn(&mut T, &U)) -> T {
+    let mut result = start;
+    for iter |x| {
+        f(&mut result, x);
+    }
+    result
+}
+
+/**
+ * Return the sum of the items yielding by an iterator.
+ *
+ * # Example:
+ *
+ * ~~~~
+ * let xs: ~[int] = ~[1, 2, 3, 4];
+ * assert_eq!(do sum |f| { xs.each(f) }, 10);
+ * ~~~~
+ */
+#[inline(always)]
+pub fn sum<T: Zero + Add<T, T>>(iter: &fn(f: &fn(&T) -> bool) -> bool) -> T {
+    fold_ref(Zero::zero::<T>(), iter, |a, x| *a = a.add(x))
+}
+
+/**
+ * Return the product of the items yielded by an iterator.
+ *
+ * # Example:
+ *
+ * ~~~~
+ * let xs: ~[int] = ~[1, 2, 3, 4];
+ * assert_eq!(do product |f| { xs.each(f) }, 24);
+ * ~~~~
+ */
+#[inline(always)]
+pub fn product<T: One + Mul<T, T>>(iter: &fn(f: &fn(&T) -> bool) -> bool) -> T {
+    fold_ref(One::one::<T>(), iter, |a, x| *a = a.mul(x))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use prelude::*;
+
+    #[test]
+    fn test_to_vec() {
+        let xs = ~[1, 2, 3];
+        let ys = do to_vec |f| { xs.each(|x| f(*x)) };
+        assert_eq!(xs, ys);
+    }
+
+    #[test]
+    fn test_any() {
+        let xs = ~[1u, 2, 3, 4, 5];
+        assert!(any(|&x: &uint| x > 2, |f| xs.each(f)));
+        assert!(!any(|&x: &uint| x > 5, |f| xs.each(f)));
+    }
+
+    #[test]
+    fn test_all() {
+        assert!(all(|x: uint| x < 6, |f| uint::range(1, 6, f)));
+        assert!(!all(|x: uint| x < 5, |f| uint::range(1, 6, f)));
+    }
+
+    #[test]
+    fn test_find() {
+        let xs = ~[1u, 2, 3, 4, 5, 6];
+        assert_eq!(*find(|& &x: & &uint| x > 3, |f| xs.each(f)).unwrap(), 4);
+    }
+
+    #[test]
+    fn test_max() {
+        let xs = ~[8, 2, 3, 1, -5, 9, 11, 15];
+        assert_eq!(max(|f| xs.each(f)).unwrap(), &15);
+    }
+
+    #[test]
+    fn test_min() {
+        let xs = ~[8, 2, 3, 1, -5, 9, 11, 15];
+        assert_eq!(min(|f| xs.each(f)).unwrap(), &-5);
+    }
+
+    #[test]
+    fn test_fold() {
+        assert_eq!(fold(0i, |f| int::range(1, 5, f), |a, x| *a += x), 10);
+    }
+
+    #[test]
+    fn test_sum() {
+        let xs: ~[int] = ~[1, 2, 3, 4];
+        assert_eq!(do sum |f| { xs.each(f) }, 10);
+    }
+
+    #[test]
+    fn test_empty_sum() {
+        let xs: ~[int] = ~[];
+        assert_eq!(do sum |f| { xs.each(f) }, 0);
+    }
+
+    #[test]
+    fn test_product() {
+        let xs: ~[int] = ~[1, 2, 3, 4];
+        assert_eq!(do product |f| { xs.each(f) }, 24);
+    }
+
+    #[test]
+    fn test_empty_product() {
+        let xs: ~[int] = ~[];
+        assert_eq!(do product |f| { xs.each(f) }, 1);
+    }
+}