src/HOL/Library/Pretty_Int.thy

 
 code_type int
   (SML "IntInf.int")
   (OCaml "Big'_int.big'_int")
   (Haskell "Integer")
+
+code_instance int :: eq
+  (Haskell -)
 
 setup {*
   fold (fn target => CodegenSerializer.add_pretty_numeral target
     (@{const_name number_of}, @{typ "int \<Rightarrow> int"})
     @{const_name Numeral.B0} @{const_name Numeral.B1}