Nasal: std.Vector: add 'contains' method (by onox).

Nasal/std/Vector.nas

@@ -120,6 +120,15 @@ var Vector = {
         die("ValueError: item not in the vector");
     },
 
+    contains: func (item) {
+        # Return true if the vector contains the item, false otherwise
+
+        var err = [];
+        call(Vector.index, [item], me, err);
+
+        return size(err) == 0;
+    },
+
     remove: func (item) {
         # Remove the first occurrence of the given item. Raises a
         # ValueError if the item is not present in the vector.

Nasal/std/Vector.nas.test

@@ -108,6 +108,10 @@ REQUIRE_EQUAL(x.size(), 4);
 # index():
 REQUIRE_EQUAL(x.index("c"), 2);
 
+# contains():
+REQUIRE_EQUAL(x.contains("c"), 1);
+REQUIRE_EQUAL(x.contains("e"), 0);
+
 # remove():
 x.remove("c");
 REQUIRE_EQUAL(x.vector, ["a", "b", "d"]);