1 files changed, 25 insertions, 0 deletions
diff --git a/stdlib/source/library/lux/abstract/equivalence.lux b/stdlib/source/library/lux/abstract/equivalence.lux
new file mode 100644
index 000000000..bb21f7711
--- /dev/null
+++ b/stdlib/source/library/lux/abstract/equivalence.lux
@@ -0,0 +1,25 @@
+(.module:
+  [library
+   [lux #*]]
+  [//
+   [functor
+    ["." contravariant]]])
+
+(interface: #export (Equivalence a)
+  {#.doc "Equivalence for a type's instances."}
+  (: (-> a a Bit)
+     =))
+
+(def: #export (rec sub)
+  (All [a] (-> (-> (Equivalence a) (Equivalence a)) (Equivalence a)))
+  (implementation
+   (def: (= left right)
+     (sub = left right))))
+
+(implementation: #export functor
+  (contravariant.Functor Equivalence)
+  
+  (def: (map f equivalence)
+    (implementation
+     (def: (= reference sample)
+       (\ equivalence = (f reference) (f sample))))))