diff --git a/src/libcore/core.rs b/src/libcore/core.rs
index f9fbe7aa9292b..12a426261c49b 100644
--- a/src/libcore/core.rs
+++ b/src/libcore/core.rs
@@ -17,7 +17,7 @@ pub use vec::{ConstVector, CopyableVector, ImmutableVector};
 pub use vec::{ImmutableEqVector, ImmutableCopyableVector};
 pub use vec::{MutableVector, MutableCopyableVector};
 pub use iter::{BaseIter, ExtendedIter, EqIter, CopyableIter};
-pub use iter::{CopyableOrderedIter, Times};
+pub use iter::{CopyableOrderedIter, CopyableNonstrictIter, Times};
 pub use num::Num;
 pub use ptr::Ptr;
 pub use to_str::ToStr;
diff --git a/src/libcore/iter.rs b/src/libcore/iter.rs
index bb28d0ef4fbac..d318c279999c2 100644
--- a/src/libcore/iter.rs
+++ b/src/libcore/iter.rs
@@ -46,6 +46,13 @@ pub trait CopyableOrderedIter<A:Copy Ord> {
     pure fn max() -> A;
 }
 
+pub trait CopyableNonstrictIter<A:Copy> {
+    // Like "each", but copies out the value. If the receiver is mutated while
+    // iterating over it, the semantics must not be memory-unsafe but are
+    // otherwise undefined.
+    pure fn each_val(&const self, f: &fn(A) -> bool);
+}
+
 // A trait for sequences that can be by imperatively pushing elements
 // onto them.
 pub trait Buildable<A> {
diff --git a/src/libcore/vec.rs b/src/libcore/vec.rs
index 24a44c591c1b6..6cbf8ca91fd63 100644
--- a/src/libcore/vec.rs
+++ b/src/libcore/vec.rs
@@ -2020,6 +2020,37 @@ impl<A: Copy Ord> &[A]: iter::CopyableOrderedIter<A> {
     pure fn min() -> A { iter::min(&self) }
     pure fn max() -> A { iter::max(&self) }
 }
+
+impl<A:Copy> &[A] : iter::CopyableNonstrictIter<A> {
+    pure fn each_val(&const self, f: fn(A) -> bool) {
+        let mut i = 0;
+        while i < self.len() {
+            if !f(copy self[i]) { break; }
+            i += 1;
+        }
+    }
+}
+
+impl<A:Copy> ~[A] : iter::CopyableNonstrictIter<A> {
+    pure fn each_val(&const self, f: fn(A) -> bool) {
+        let mut i = 0;
+        while i < self.len() {
+            if !f(copy self[i]) { break; }
+            i += 1;
+        }
+    }
+}
+
+impl<A:Copy> @[A] : iter::CopyableNonstrictIter<A> {
+    pure fn each_val(&const self, f: fn(A) -> bool) {
+        let mut i = 0;
+        while i < self.len() {
+            if !f(copy self[i]) { break; }
+            i += 1;
+        }
+    }
+}
+
 // ___________________________________________________________________________
 
 #[cfg(test)]