Added two version of reverse and a swap function to the standard library.

src/lib/vec.rs

@@ -322,6 +322,45 @@ fn freeze[T](vec[mutable T] v) -> vec[T] {
     ret result;
 }
 
+// Swaps two elements in a vector
+fn swap[T](&vec[T] v, uint a, uint b) {
+    let T t = v.(a);
+    v.(a) = v.(b);
+    v.(b) = t;
+}
+
+// In place vector reversal
+fn reverse[T](&vec[T] v) -> () {
+    let uint i = 0u;
+    auto ln = len[T](v);
+
+    while(i < ln / 2u) {
+        swap(v, i, ln - i - 1u);
+        i += 1u;
+    }
+}
+
+// Functional vector reversal. Returns a reversed copy of v.
+fn reversed[T](vec[T] v) -> vec[T] {
+    let vec[T] res = [];
+
+    auto i = len[T](v);
+    if (i == 0u) {
+        ret res;
+    }
+    else {
+        i -= 1u;
+    }
+
+    while(i != 0u) {
+        push[T](res, v.(i));
+        i -= 1u;
+    }
+    push[T](res, v.(0));
+
+    ret res;
+}
+
 // Local Variables:
 // mode: rust;
 // fill-column: 78;

src/test/run-pass/vec-reverse.rs

@@ -0,0 +1,29 @@
+use std;
+import std::vec;
+
+fn main() {
+  let vec[int] v = [10, 20];
+
+  assert v.(0) == 10;
+  assert v.(1) == 20;
+
+  vec::reverse[int](v);
+
+  assert v.(0) == 20;
+  assert v.(1) == 10;
+
+  auto v2 = vec::reversed[int](v);
+
+  assert v2.(0) == 10;
+  assert v2.(1) == 20;
+
+  v.(0) = 30;
+
+  assert v2.(0) == 10;
+
+  // Make sure they work with 0-length vectors too.
+  let vec[int] v3 = [];
+  auto v4 = vec::reversed[int](v3);
+
+  vec::reverse[int](v3);
+}