1 files changed, 18 insertions, 1 deletions
diff --git a/stdlib/source/lux/data/sum.lux b/stdlib/source/lux/data/sum.lux
index 2f7624113..5b7dc5a61 100644
--- a/stdlib/source/lux/data/sum.lux
+++ b/stdlib/source/lux/data/sum.lux
@@ -1,6 +1,8 @@
 (.module:
   {#.doc "Functionality for working with variants (particularly 2-variants)."}
-  lux)
+  [lux #*
+   [abstract
+    [equivalence (#+ Equivalence)]]])
 
 (template [<name> <type> <index>]
   [(def: #export (<name> value)
@@ -51,3 +53,18 @@
       (case x
         (0 x')  [(#.Cons x' lefts) rights]
         (1 x') [lefts (#.Cons x' rights)]))))
+
+(structure: #export (equivalence l@= r@=)
+  (All [l r]
+    (-> (Equivalence l) (Equivalence r)
+        (Equivalence (| l r))))
+  (def: (= reference sample)
+    (case [reference sample]
+      [(#.Left reference) (#.Left sample)]
+      (l@= reference sample)
+      
+      [(#.Right reference) (#.Right sample)]
+      (r@= reference sample)
+
+      _
+      false)))