core: add Pair.reverse and Map.reverse

core/Map.carp

@@ -276,6 +276,9 @@
                          @"{"
                          m)]
       (String.append &res " }")))
+
+  (defn reverse [m]
+    (from-array &(Array.copy-map &Pair.reverse &(to-array m))))
 )
 
 (deftype (SetBucket a) [entries (Array a)])

core/Tuples.carp

@@ -33,4 +33,7 @@
   (defn > [p1 p2]
     (PairRef.> &p1 &p2))
 
+  (doc reverse "reverses a `Pair` `p` such that its first member is its second member and vice versa.")
+  (defn reverse [p]
+    (Pair.init @(Pair.b p) @(Pair.a p)))
   )

test/map.carp

@@ -197,6 +197,11 @@
                 (Map.get &{(Pair.init 1 2) 3} &(Pair.init 1 2))
                 "Pairs work as keys"
   )
+  (assert-equal test
+                &{1 @"hi" 2 @"bye"}
+                &(Map.reverse &{@"hi" 1 @"bye" 2})
+                "reverse works"
+  )
   (assert-equal test
                 1
                 (Set.length &(Set.put (Set.create) "1"))

test/tuples.carp

@@ -21,4 +21,9 @@
                "comparison works with (Ref (Pair String Int)) I")
   (assert-false test
                 (< &(Pair.init @"a" 2) &(Pair.init @"a" 1))
-                "comparison works with (Ref (Pair String Int)) II"))
+                "comparison works with (Ref (Pair String Int)) II")
+  (assert-equal test
+                &(Pair.init 2 @"a")
+                &(Pair.reverse &(Pair.init @"a" 2))
+                "reverse works")
+)