src/HOL/Tools/Predicate_Compile/predicate_compile_specialisation.ML

modernized structure Proof_Context;

(*  Title:      HOL/Tools/Predicate_Compile/predicate_compile_specialisation.ML
    Author:     Lukas Bulwahn, TU Muenchen

Deriving specialised predicates and their intro rules
*)

signature PREDICATE_COMPILE_SPECIALISATION =
sig
  val find_specialisations : string list -> (string * thm list) list -> theory -> (string * thm list) list * theory
end;

structure Predicate_Compile_Specialisation : PREDICATE_COMPILE_SPECIALISATION =
struct

open Predicate_Compile_Aux;

(* table of specialisations *)
structure Specialisations = Theory_Data
(
  type T = (term * term) Item_Net.T;
  val empty : T = Item_Net.init (op aconv o pairself fst) (single o fst);
  val extend = I;
  val merge = Item_Net.merge;
)

fun specialisation_of thy atom =
  Item_Net.retrieve (Specialisations.get thy) atom

fun print_specialisations thy =
  tracing (cat_lines (map (fn (t, spec_t) =>
      Syntax.string_of_term_global thy t ^ " ~~~> " ^ Syntax.string_of_term_global thy spec_t)
    (Item_Net.content (Specialisations.get thy))))

fun import (pred, intros) args ctxt =
  let
    val thy = Proof_Context.theory_of ctxt
    val ((Tinst, intros'), ctxt') = Variable.importT intros ctxt
    val pred' = fst (strip_comb (HOLogic.dest_Trueprop (Logic.strip_imp_concl (prop_of (hd intros')))))
    val Ts = binder_types (fastype_of pred')
    val argTs = map fastype_of args
    val Tsubst = Type.raw_matches (argTs, Ts) Vartab.empty
    val args' = map (Envir.subst_term_types Tsubst) args
  in
    (((pred', intros'), args'), ctxt')
  end

(* patterns only constructed of variables and pairs/tuples are trivial constructor terms*)
fun is_nontrivial_constrt thy t =
  let
    val cnstrs = flat (maps
      (map (fn (_, (Tname, _, cs)) => map (apsnd (rpair Tname o length)) cs) o #descr o snd)
      (Symtab.dest (Datatype.get_all thy)));
    fun check t = (case strip_comb t of
        (Var _, []) => (true, true)
      | (Free _, []) => (true, true)
      | (Const (@{const_name Pair}, _), ts) =>
        pairself (forall I) (split_list (map check ts))
      | (Const (s, T), ts) => (case (AList.lookup (op =) cnstrs s, body_type T) of
            (SOME (i, Tname), Type (Tname', _)) => (false,
              length ts = i andalso Tname = Tname' andalso forall (snd o check) ts)
          | _ => (false, false))
      | _ => (false, false))
  in check t = (false, true) end;

fun specialise_intros black_list (pred, intros) pats thy =
  let
    val ctxt = Proof_Context.init_global thy
    val maxidx = fold (Term.maxidx_term o prop_of) intros ~1
    val pats = map (Logic.incr_indexes ([],  maxidx + 1)) pats
    val (((pred, intros), pats), ctxt') = import (pred, intros) pats ctxt
    val intros_t = map prop_of intros
    val result_pats = map Var (fold_rev Term.add_vars pats [])
    fun mk_fresh_name names =
      let
        val name =
          Name.variant names ("specialised_" ^ Long_Name.base_name (fst (dest_Const pred)))
        val bname = Sign.full_bname thy name
      in
        if Sign.declared_const thy bname then
          mk_fresh_name (name :: names)
        else
          bname
      end
    val constname = mk_fresh_name []
    val constT = map fastype_of result_pats ---> @{typ bool}
    val specialised_const = Const (constname, constT)
    val specialisation =
      [(HOLogic.mk_Trueprop (list_comb (pred, pats)),
        HOLogic.mk_Trueprop (list_comb (specialised_const, result_pats)))]
    fun specialise_intro intro =
      (let
        val (prems, concl) = Logic.strip_horn (prop_of intro)
        val env = Pattern.unify thy
          (HOLogic.mk_Trueprop (list_comb (pred, pats)), concl) (Envir.empty 0)
        val prems = map (Envir.norm_term env) prems
        val args = map (Envir.norm_term env) result_pats
        val concl = HOLogic.mk_Trueprop (list_comb (specialised_const, args))
        val intro = Logic.list_implies (prems, concl)
      in
        SOME intro
      end handle Pattern.Unif => NONE)
    val specialised_intros_t = map_filter I (map specialise_intro intros)
    val thy' = Sign.add_consts_i [(Binding.name (Long_Name.base_name constname), constT, NoSyn)] thy
    val specialised_intros = map (Skip_Proof.make_thm thy') specialised_intros_t
    val exported_intros = Variable.exportT ctxt' ctxt specialised_intros
    val [t, specialised_t] = Variable.exportT_terms ctxt' ctxt
      [list_comb (pred, pats), list_comb (specialised_const, result_pats)]
    val thy'' = Specialisations.map (Item_Net.update (t, specialised_t)) thy'
    val optimised_intros =
      map_filter (Predicate_Compile_Aux.peephole_optimisation thy'') exported_intros
    val ([spec], thy''') = find_specialisations black_list [(constname, optimised_intros)] thy''
    val thy'''' = Core_Data.register_intros spec thy'''
  in
    thy''''
  end

and find_specialisations black_list specs thy =
  let
    val add_vars = fold_aterms (fn Var v => cons v | _ => I);
    fun fresh_free T free_names =
      let
        val free_name = Name.variant free_names "x"
      in
        (Free (free_name, T), free_name :: free_names)
      end
    fun replace_term_and_restrict thy T t Tts free_names =
      let
        val (free, free_names') = fresh_free T free_names
        val Tts' = map (apsnd (Pattern.rewrite_term thy [(t, free)] [])) Tts
        val (ts', free_names'') = restrict_pattern' thy Tts' free_names'
      in
        (free :: ts', free_names'')
      end
    and restrict_pattern' thy [] free_names = ([], free_names)
      | restrict_pattern' thy ((T, Free (x, _)) :: Tts) free_names =
      let
        val (ts', free_names') = restrict_pattern' thy Tts free_names
      in
        (Free (x, T) :: ts', free_names')
      end
      | restrict_pattern' thy ((T as TFree _, t) :: Tts) free_names =
        replace_term_and_restrict thy T t Tts free_names
      | restrict_pattern' thy ((T as Type (Tcon, Ts), t) :: Tts) free_names =
        case Datatype_Data.get_constrs thy Tcon of
          NONE => replace_term_and_restrict thy T t Tts free_names
        | SOME constrs => (case strip_comb t of
          (Const (s, _), ats) => (case AList.lookup (op =) constrs s of
            SOME constr_T =>
              let
                val (Ts', T') = strip_type constr_T
                val Tsubst = Type.raw_match (T', T) Vartab.empty
                val Ts = map (Envir.subst_type Tsubst) Ts'
                val (bts', free_names') = restrict_pattern' thy ((Ts ~~ ats) @ Tts) free_names
                val (ats', ts') = chop (length ats) bts'
              in
                (list_comb (Const (s, map fastype_of ats' ---> T), ats') :: ts', free_names')
              end
            | NONE => replace_term_and_restrict thy T t Tts free_names))
    fun restrict_pattern thy Ts args =
      let
        val args = map Logic.unvarify_global args
        val Ts = map Logic.unvarifyT_global Ts
        val free_names = fold Term.add_free_names args []
        val (pat, _) = restrict_pattern' thy (Ts ~~ args) free_names
      in map Logic.varify_global pat end
    fun detect' atom thy =
      case strip_comb atom of
        (pred as Const (pred_name, _), args) =>
          let
          val Ts = binder_types (Sign.the_const_type thy pred_name)
          val vnames = map fst (fold Term.add_var_names args [])
          val pats = restrict_pattern thy Ts args
        in
          if (exists (is_nontrivial_constrt thy) pats)
            orelse (has_duplicates (op =) (fold add_vars pats [])) then
            let
              val thy' =
                case specialisation_of thy atom of
                  [] =>
                    if member (op =) ((map fst specs) @ black_list) pred_name then
                      thy
                    else
                      (case try (Core_Data.intros_of (Proof_Context.init_global thy)) pred_name of
                        NONE => thy
                      | SOME [] => thy
                      | SOME intros =>
                          specialise_intros ((map fst specs) @ (pred_name :: black_list))
                            (pred, intros) pats thy)
                  | (t, specialised_t) :: _ => thy
                val atom' =
                  case specialisation_of thy' atom of
                    [] => atom
                  | (t, specialised_t) :: _ =>
                    let
                      val subst = Pattern.match thy' (t, atom) (Vartab.empty, Vartab.empty)
                    in Envir.subst_term subst specialised_t end handle Pattern.MATCH => atom
                    (*FIXME: this exception could be caught earlier in specialisation_of *)
            in
              (atom', thy')
            end
          else (atom, thy)
        end
      | _ => (atom, thy)
    fun specialise' (constname, intros) thy =
      let
        (* FIXME: only necessary because of sloppy Logic.unvarify in restrict_pattern *)
        val intros = Drule.zero_var_indexes_list intros
        val (intros_t', thy') = (fold_map o fold_map_atoms) detect' (map prop_of intros) thy
      in
        ((constname, map (Skip_Proof.make_thm thy') intros_t'), thy')
      end
  in
    fold_map specialise' specs thy
  end

end;