\lambda A,B,C:Type.\lambda f:(B\to C).\lambda g:(A\to B).\lambda x:A.
f (g x).
-interpretation "function composition" 'compose f g = (compose _ _ _ f g).
+interpretation "function composition" 'compose f g = (compose ? ? ? f g).
definition injective: \forall A,B:Type.\forall f:A \to B.Prop
\def \lambda A,B.\lambda f.