1 files changed, 7 insertions, 5 deletions
diff --git a/stdlib/source/lux/data/sum.lux b/stdlib/source/lux/data/sum.lux
index 716b3908a..ade411e6b 100644
--- a/stdlib/source/lux/data/sum.lux
+++ b/stdlib/source/lux/data/sum.lux
@@ -10,11 +10,13 @@
   [left  a +0]
   [right b +1])
 
-(def: #export (either f g s)
-  (All [a b c] (-> (-> a c) (-> b c) (| a b) c))
-  (case s
-    (+0 x)  (f x)
-    (+1 x) (g x)))
+(def: #export (either f g)
+  (All [a b c] (-> (-> a c) (-> b c)
+                   (-> (| a b) c)))
+  (lambda [input]
+    (case input
+      (+0 l) (f l)
+      (+1 r) (g r))))
 
 (do-template [<name> <side> <tag>]
   [(def: #export (<name> es)