--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/record_functor.agda	Fri Feb 13 11:31:46 2015 +0900
@@ -0,0 +1,11 @@
+record Functor {l : Level} (F : Set l -> Set l) : Set (suc l) where
+ field
+  fmap : {A B : Set l} -> (A -> B) -> (F A) -> (F B)
+ field -- laws
+  preserve-id : {A : Set l} (x : F A) → fmap id x ≡ id x
+  covariant   : {A B C : Set l} (f : A -> B) -> (g : B -> C) -> (x : F A)
+                   -> fmap (g ∙ f) x ≡ ((fmap g) ∙ (fmap f)) x
+ field -- proof assistant
+  fmap-equiv : {A B : Set l} {f g : A -> B} ->
+    ((x : A) -> f x ≡ g x) -> (fx : F A) -> fmap f fx ≡ fmap g fx
+