[sledge] Add Trm.pp_diff and expose Trm.pp

Reviewed By: ngorogiannis

Differential Revision: D24532354

fbshipit-source-id: e51393786

sledge/src/trm.ml

@@ -390,6 +390,8 @@ type arith = Arith.t
 
 include Trm
 
+let pp_diff fs (x, y) = Format.fprintf fs "-- %a ++ %a" pp x pp y
+
 (** Construct *)
 
 (* variables *)

sledge/src/trm.mli

@@ -42,6 +42,8 @@ module Arith :
   Arithmetic.S with type var := Var.t with type trm := t with type t = arith
 
 val ppx : Var.strength -> t pp
+val pp : t pp
+val pp_diff : (t * t) pp
 
 (** Construct *)