refactor: explicit recursion in preprocessing

if a preprocessor fires, it's up to it to preprocess subterms. rewriting
is now from the root, not the leaves on.

Use that in LRA to rewrite under linear expressions.

src/arith/base-term/Base_types.ml

@@ -209,7 +209,7 @@ let string_of_lra_pred = function
   | Leq -> "<="
   | Neq -> "!="
   | Eq -> "="
-  | Gt-> ">"
+  | Gt -> ">"
   | Geq -> ">="
 let pp_pred out p = Fmt.string out (string_of_lra_pred p)
 

src/arith/lra/Sidekick_arith_lra.ml

@@ -142,22 +142,22 @@ module Make(A : ARG) : S with module A = A = struct
     let t = fresh_term ~pre self Ty.bool in
     mk_lit t
 
-  (* turn the term into a linear expression *)
-  let rec as_linexp (t:T.t) : LE.t =
+  (* turn the term into a linear expression. Apply [f] on leaves. *)
+  let rec as_linexp ~f (t:T.t) : LE.t =
     let open LE.Infix in
     match A.view_as_lra t with
-    | LRA_other _ -> LE.var t
+    | LRA_other _ -> LE.var (f t)
     | LRA_pred _ ->
       Error.errorf "type error: in linexp, LRA predicate %a" T.pp t
     | LRA_op (op, t1, t2) ->
-      let t1 = as_linexp t1 in
-      let t2 = as_linexp t2 in
+      let t1 = as_linexp ~f t1 in
+      let t2 = as_linexp ~f t2 in
       begin match op with
         | Plus -> t1 + t2
         | Minus -> t1 - t2
       end
     | LRA_mult (n, x) ->
-      let t = as_linexp x in
+      let t = as_linexp ~f x in
       LE.( n * t )
     | LRA_const q -> LE.const q
 
@@ -166,21 +166,19 @@ module Make(A : ARG) : S with module A = A = struct
      *)
 
   (* preprocess linear expressions away *)
-  let preproc_lra self si ~mk_lit:_ ~add_clause:_ (t:T.t) : T.t option =
+  let preproc_lra self si ~recurse ~mk_lit:_ ~add_clause:_ (t:T.t) : T.t option =
     Log.debugf 50 (fun k->k "lra.preprocess %a" T.pp t);
     let _tst = SI.tst si in
     match A.view_as_lra t with
     | LRA_pred (pred, t1, t2) ->
-      (* TODO: map preproc on [l1] and [l2] *)
-      let l1 = as_linexp t1 in
-      let l2 = as_linexp t2 in
+      let l1 = as_linexp ~f:recurse t1 in
+      let l2 = as_linexp ~f:recurse t2 in
       let proxy = fresh_term self ~pre:"_pred_lra_" Ty.bool in
       T.Tbl.add self.pred_defs proxy (pred, l1, l2);
       Log.debugf 5 (fun k->k"lra.preprocess.step %a :into %a" T.pp t T.pp proxy);
       Some proxy
     | LRA_op _ | LRA_mult _ ->
-      let le = as_linexp t in
-      (* TODO: map preproc on [le] *)
+      let le = as_linexp ~f:recurse t in
       let proxy = fresh_term self ~pre:"_e_lra_" (T.ty t) in
       self.t_defs <- (proxy, le) :: self.t_defs;
       Log.debugf 5 (fun k->k"lra.preprocess.step %a :into %a" T.pp t T.pp proxy);

src/arith/lra/fourier_motzkin.ml

@@ -59,6 +59,8 @@ module type S = sig
     val find_exn : term -> t -> Q.t
     val find : term -> t -> Q.t option
 
+(*     val map : (term -> term) -> t -> t *)
+
     module Infix : sig
       val (+) : t -> t -> t
       val (-) : t -> t -> t
@@ -112,10 +114,10 @@ module Make(A : ARG)
     let zero = const Q.zero
     let var x : t = {const=Q.zero; le=M.singleton x Q.one}
 
-    let find_exn v le = M.find v le.le
-    let find v le = M.get v le.le
+    let[@inline] find_exn v le = M.find v le.le
+    let[@inline] find v le = M.get v le.le
 
-    let remove v le : t = {le with le=M.remove v le.le}
+    let[@inline] remove v le : t = {le with le=M.remove v le.le}
 
     let neg a : t =
       {const=Q.neg a.const;

src/core/Sidekick_core.ml

@@ -481,11 +481,16 @@ module type SOLVER_INTERNAL = sig
 
   type preprocess_hook =
     t ->
+    recurse:(term -> term) ->
     mk_lit:(term -> lit) ->
     add_clause:(lit list -> unit) ->
     term -> term option
   (** Given a term, try to preprocess it. Return [None] if it didn't change.
-      Can also add clauses to define new terms. *)
+      Can also add clauses to define new terms.
+      @param recurse call preprocessor on subterms.
+      @param mk_lit creates a new literal for a boolean term.
+      @param add_clause pushes a new clause into the SAT solver.
+  *)
 
   val add_preprocess : t -> preprocess_hook -> unit
 end

src/msat-solver/Sidekick_msat_solver.ml

@@ -174,6 +174,7 @@ module Make(A : ARG)
 
     and preprocess_hook =
       t ->
+      recurse:(term -> term) ->
       mk_lit:(term -> lit) ->
       add_clause:(lit list -> unit) ->
       term -> term option
@@ -223,23 +224,27 @@ module Make(A : ARG)
         match Term.Tbl.find self.preprocess_cache t with
         | u -> u
         | exception Not_found ->
-          (* first, map subterms *)
-          let u = Term.map_shallow self.tst aux t in
-          (* then rewrite *)
-          let u = aux_rec u self.preprocess in
+          (* try rewrite here *)
+          let u =
+            match aux_rec t self.preprocess with
+            | None ->
+              Term.map_shallow self.tst aux t (* just map subterms *)
+            | Some u -> u
+          in
           Term.Tbl.add self.preprocess_cache t u;
           u
       (* try each function in [hooks] successively *)
       and aux_rec t hooks = match hooks with
-        | [] -> t
+        | [] -> None
         | h :: hooks_tl ->
-          match h self ~mk_lit ~add_clause t with
+          match h self ~recurse:aux ~mk_lit ~add_clause t with
           | None -> aux_rec t hooks_tl
           | Some u ->
-            Log.debugf 30 
+            Log.debugf 30
               (fun k->k "(@[msat-solver.preprocess.step@ :from %a@ :to %a@])"
                   Term.pp t Term.pp u);
-            aux u
+            let u' = aux u in
+            Some u'
       in
       let t = Lit.term lit |> simp_t self |> aux in
       let lit' = Lit.atom self.tst ~sign:(Lit.sign lit) t in

src/smtlib/Typecheck.ml

@@ -294,9 +294,8 @@ let rec conv_term (ctx:Ctx.t) (t:PA.term) : T.t =
       | PA.Div, [a;b] ->
         begin match t_as_q a, t_as_q b with
           | Some a, Some b -> T.lra ctx.tst (LRA_const (Q.div a b))
-          | Some a, _ -> T.lra ctx.tst (LRA_mult (Q.inv a, b))
           | _, Some b -> T.lra ctx.tst (LRA_mult (Q.inv b, a))
-          | None, None ->
+          | _, None ->
             errorf_ctx ctx "cannot handle non-linear div %a" PA.pp_term t
         end
       | _ ->

src/th-bool-static/Sidekick_th_bool_static.ml

@@ -84,7 +84,7 @@ module Make(A : ARG) : S with module A = A = struct
 
   let is_true t = match T.as_bool t with Some true -> true | _ -> false
   let is_false t = match T.as_bool t with Some false -> true | _ -> false
-    
+
   let simplify (self:state) (simp:SI.Simplify.t) (t:T.t) : T.t option =
     let tst = self.tst in
     match A.view_as_bool t with
@@ -133,18 +133,26 @@ module Make(A : ARG) : S with module A = A = struct
     mk_lit t
 
   (* preprocess "ite" away *)
-  let preproc_ite self _si ~mk_lit ~add_clause (t:T.t) : T.t option =
+  let preproc_ite self _si ~recurse ~mk_lit ~add_clause (t:T.t) : T.t option =
     match A.view_as_bool t with
     | B_ite (a,b,c) ->
-      let t_a = fresh_term self ~pre:"ite" (T.ty b) in
-      let lit_a = mk_lit a in
-      add_clause [Lit.neg lit_a; mk_lit (eq self.tst t_a b)];
-      add_clause [lit_a; mk_lit (eq self.tst t_a c)];
-      Some t_a
+      let a = recurse a in
+      begin match A.view_as_bool a with
+        | B_bool true -> Some (recurse b)
+        | B_bool false -> Some (recurse c)
+        | _ ->
+          let t_a = fresh_term self ~pre:"ite" (T.ty b) in
+          let lit_a = mk_lit a in
+          let b = recurse b in
+          let c = recurse c in
+          add_clause [Lit.neg lit_a; mk_lit (eq self.tst t_a b)];
+          add_clause [lit_a; mk_lit (eq self.tst t_a c)];
+          Some t_a
+      end
     | _ -> None
 
   (* TODO: polarity? *)
-  let cnf (self:state) (_si:SI.t) ~mk_lit ~add_clause (t:T.t) : T.t option =
+  let cnf (self:state) (_si:SI.t) ~recurse:_ ~mk_lit ~add_clause (t:T.t) : T.t option =
     let rec get_lit (t:T.t) : Lit.t =
       let t_abs, t_sign = T.abs self.tst t in
       let lit =
@@ -217,6 +225,7 @@ module Make(A : ARG) : S with module A = A = struct
     in
     let cnf_of t =
       cnf self si t
+        ~recurse:(fun t -> t)
         ~mk_lit:(SI.mk_lit si acts) ~add_clause:(SI.add_clause_permanent si acts)
     in
     begin