stdlib: Implement interior vector map

src/lib/ivec.rs

@@ -158,6 +158,20 @@ fn grow_set[T](&mutable T[mutable] v, uint index, &T initval, &T val) {
     v.(index) = val;
 }
 
+
+// Functional utilities
+
+fn map[T,U](fn(&T)->U f, &mutable T[mutable?] v) -> U[] {
+    auto result = ~[];
+    reserve(result, len(v));
+    for (T elem in v) {
+        auto elem2 = elem;  // satisfies alias checker
+        result += ~[f(elem2)];
+    }
+    ret result;
+}
+
+
 mod unsafe {
     fn copy_from_buf[T](&mutable T[] v, *T ptr, uint count) {
         ret rustrt::ivec_copy_from_buf(v, ptr, count);

src/test/run-pass/lib-ivec.rs

@@ -164,6 +164,26 @@ fn test_grow_set() {
     assert (v.(4) == 5);
 }
 
+fn test_map() {
+    // Test on-stack map.
+    auto v = ~[ 1u, 2u, 3u ];
+    auto w = ivec::map(square, v);
+    assert (ivec::len(w) == 3u);
+    assert (w.(0) == 1u);
+    assert (w.(1) == 4u);
+    assert (w.(2) == 9u);
+
+    // Test on-heap map.
+    v = ~[ 1u, 2u, 3u, 4u, 5u ];
+    w = ivec::map(square, v);
+    assert (ivec::len(w) == 5u);
+    assert (w.(0) == 1u);
+    assert (w.(1) == 4u);
+    assert (w.(2) == 9u);
+    assert (w.(3) == 16u);
+    assert (w.(4) == 25u);
+}
+
 fn main() {
     test_reserve_and_on_heap();
     test_unsafe_ptrs();
@@ -181,5 +201,8 @@ fn main() {
     test_grow();
     test_grow_fn();
     test_grow_set();
+
+    // Functional utilities
+    test_map();
 }