1 files changed, 27 insertions, 0 deletions
diff --git a/stdlib/source/library/lux/abstract/hash.lux b/stdlib/source/library/lux/abstract/hash.lux
new file mode 100644
index 000000000..2cc18f3e4
--- /dev/null
+++ b/stdlib/source/library/lux/abstract/hash.lux
@@ -0,0 +1,27 @@
+(.module:
+  [library
+   [lux #*]]
+  [//
+   ["." equivalence (#+ Equivalence)]
+   [functor
+    ["." contravariant]]])
+
+(interface: #export (Hash a)
+  {#.doc (doc "A way to produce hash-codes for a type's instances."
+              "A necessity when working with some data-structures, such as dictionaries or sets.")}
+  (: (Equivalence a)
+     &equivalence)
+  (: (-> a Nat)
+     hash))
+
+(implementation: #export functor
+  (contravariant.Functor Hash)
+  
+  (def: (map f super)
+    (implementation
+     (def: &equivalence
+       (\ equivalence.functor map f
+          (\ super &equivalence)))
+     
+     (def: hash
+       (|>> f (\ super hash))))))