src/Provers/simplifier.ML

better miniscoping rules: the premise C~={} is not good
because Safe_tac eliminates such assumptions.

(*  Title:      Provers/simplifier.ML
    ID:         $Id$
    Author:     Tobias Nipkow and Markus Wenzel, TU Muenchen

Generic simplifier, suitable for most logics.  See Pure/thm.ML for the
actual meta-level rewriting engine.
*)

infix 4
  setsubgoaler setloop addloop delloop setSSolver addSSolver setSolver
  addSolver addsimps delsimps addeqcongs deleqcongs
  setmksimps setmkeqTrue setmksym settermless addsimprocs delsimprocs;

signature BASIC_SIMPLIFIER =
sig
  type simproc
  val mk_simproc: string -> cterm list
    -> (Sign.sg -> thm list -> term -> thm option) -> simproc
  type simpset
  val empty_ss: simpset
  val rep_ss: simpset ->
   {mss: meta_simpset,
    subgoal_tac:        simpset -> int -> tactic,
    loop_tacs:          (string * (int -> tactic))list,
           finish_tac: thm list -> int -> tactic,
    unsafe_finish_tac: thm list -> int -> tactic};
  val print_ss: simpset -> unit
  val print_simpset: theory -> unit
  val setsubgoaler: simpset *  (simpset -> int -> tactic) -> simpset
  val setloop:      simpset *             (int -> tactic) -> simpset
  val addloop:      simpset *  (string * (int -> tactic)) -> simpset
  val delloop:      simpset *   string                    -> simpset
  val setSSolver:   simpset * (thm list -> int -> tactic) -> simpset
  val addSSolver:   simpset * (thm list -> int -> tactic) -> simpset
  val setSolver:    simpset * (thm list -> int -> tactic) -> simpset
  val addSolver:    simpset * (thm list -> int -> tactic) -> simpset
  val setmksimps:   simpset * (thm -> thm list) -> simpset
  val setmkeqTrue:  simpset * (thm -> thm option) -> simpset
  val setmksym:     simpset * (thm -> thm option) -> simpset
  val settermless:  simpset * (term * term -> bool) -> simpset
  val addsimps:     simpset * thm list -> simpset
  val delsimps:     simpset * thm list -> simpset
  val addeqcongs:   simpset * thm list -> simpset
  val deleqcongs:   simpset * thm list -> simpset
  val addsimprocs:  simpset * simproc list -> simpset
  val delsimprocs:  simpset * simproc list -> simpset
  val merge_ss:     simpset * simpset -> simpset
  val prems_of_ss:  simpset -> thm list
  val simpset_ref_of_sg: Sign.sg -> simpset ref
  val simpset_ref_of: theory -> simpset ref
  val simpset_of_sg: Sign.sg -> simpset
  val simpset_of: theory -> simpset
  val SIMPSET: (simpset -> tactic) -> tactic
  val SIMPSET': (simpset -> 'a -> tactic) -> 'a -> tactic
  val simpset: unit -> simpset
  val simpset_ref: unit -> simpset ref
  val Addsimps: thm list -> unit
  val Delsimps: thm list -> unit
  val Addsimprocs: simproc list -> unit
  val Delsimprocs: simproc list -> unit
  val               simp_tac: simpset -> int -> tactic
  val           asm_simp_tac: simpset -> int -> tactic
  val          full_simp_tac: simpset -> int -> tactic
  val        asm_lr_simp_tac: simpset -> int -> tactic
  val      asm_full_simp_tac: simpset -> int -> tactic
  val safe_asm_full_simp_tac: simpset -> int -> tactic
  val               Simp_tac:            int -> tactic
  val           Asm_simp_tac:            int -> tactic
  val          Full_simp_tac:            int -> tactic
  val        Asm_lr_simp_tac:            int -> tactic
  val      Asm_full_simp_tac:            int -> tactic
  val          simplify: simpset -> thm -> thm
  val      asm_simplify: simpset -> thm -> thm
  val     full_simplify: simpset -> thm -> thm
  val asm_full_simplify: simpset -> thm -> thm
end;

signature SIMPLIFIER =
sig
  include BASIC_SIMPLIFIER
  val          rewrite: simpset -> cterm -> thm
  val      asm_rewrite: simpset -> cterm -> thm
  val     full_rewrite: simpset -> cterm -> thm
  val asm_full_rewrite: simpset -> cterm -> thm
  val print_local_simpset: Proof.context -> unit
  val get_local_simpset: Proof.context -> simpset
  val put_local_simpset: simpset -> Proof.context -> Proof.context
  val simp_add_global: theory attribute
  val simp_del_global: theory attribute
  val simp_add_local: Proof.context attribute
  val simp_del_local: Proof.context attribute
  val simp_modifiers: (Args.T list -> (Proof.context attribute * Args.T list)) list
  val setup: (theory -> theory) list
end;

structure Simplifier: SIMPLIFIER =
struct


(** simplification procedures **)

(* datatype simproc *)

datatype simproc =
  Simproc of string * cterm list * (Sign.sg -> thm list -> term -> thm option) * stamp;

fun mk_simproc name lhss proc =
  Simproc (name, map (Thm.cterm_fun Logic.varify) lhss, proc, stamp ());

fun rep_simproc (Simproc args) = args;



(** simplification sets **)

(* type simpset *)

datatype simpset =
  Simpset of {
    mss: meta_simpset,
    subgoal_tac:        simpset -> int -> tactic,
    loop_tacs:          (string * (int -> tactic))list,
           finish_tac: thm list -> int -> tactic,
    unsafe_finish_tac: thm list -> int -> tactic};

fun make_ss (mss, subgoal_tac, loop_tacs, finish_tac, unsafe_finish_tac) =
  Simpset {mss = mss, subgoal_tac = subgoal_tac, loop_tacs = loop_tacs,
    finish_tac = finish_tac, unsafe_finish_tac = unsafe_finish_tac};

val empty_ss =
  let val mss = Thm.set_mk_sym(Thm.empty_mss, Some o symmetric_fun)
  in make_ss (mss, K (K no_tac), [], K (K no_tac), K (K no_tac)) end;

fun rep_ss (Simpset args) = args;
fun prems_of_ss (Simpset {mss, ...}) = Thm.prems_of_mss mss;


(* print simpsets *)

fun print_ss ss =
  let
    val Simpset {mss, ...} = ss;
    val {simps, procs, congs} = Thm.dest_mss mss;

    val pretty_thms = map Display.pretty_thm;
    fun pretty_proc (name, lhss) =
      Pretty.big_list (name ^ ":") (map Display.pretty_cterm lhss);
  in
    Pretty.writeln (Pretty.big_list "simplification rules:" (pretty_thms simps));
    Pretty.writeln (Pretty.big_list "simplification procedures:" (map pretty_proc procs));
    Pretty.writeln (Pretty.big_list "congruences:" (pretty_thms congs))
  end;


(* extend simpsets *)

fun (Simpset {mss, subgoal_tac = _, loop_tacs, finish_tac, unsafe_finish_tac})
    setsubgoaler subgoal_tac =
  make_ss (mss, subgoal_tac, loop_tacs, finish_tac, unsafe_finish_tac);

fun (Simpset {mss, subgoal_tac, loop_tacs = _, finish_tac, unsafe_finish_tac})
    setloop tac =
  make_ss (mss, subgoal_tac, [("",tac)], finish_tac, unsafe_finish_tac);

fun (Simpset {mss, subgoal_tac, loop_tacs, finish_tac, unsafe_finish_tac})
    addloop tac = make_ss (mss, subgoal_tac, 
        (case assoc_string (loop_tacs,(fst tac)) of None => () | Some x => 
         warning ("overwriting looper "^fst tac); overwrite(loop_tacs,tac)),
           finish_tac, unsafe_finish_tac);

fun (ss as Simpset {mss,subgoal_tac,loop_tacs,finish_tac,unsafe_finish_tac})
    delloop name =
  let val (del,rest) = partition (fn (n,_) => n=name) loop_tacs
  in if null del then (warning ("No such looper in simpset: " ^ name); ss)
     else make_ss (mss, subgoal_tac, rest, finish_tac, unsafe_finish_tac)
  end;

fun (Simpset {mss, subgoal_tac, loop_tacs, finish_tac = _, unsafe_finish_tac})
    setSSolver finish_tac =
  make_ss (mss, subgoal_tac, loop_tacs, finish_tac, unsafe_finish_tac);

fun (Simpset {mss, subgoal_tac, loop_tacs, finish_tac, unsafe_finish_tac})
    addSSolver tac =
  make_ss (mss, subgoal_tac, loop_tacs, fn hyps => finish_tac hyps ORELSE' tac hyps,
    unsafe_finish_tac);

fun (Simpset {mss, subgoal_tac, loop_tacs, finish_tac, unsafe_finish_tac = _})
    setSolver unsafe_finish_tac =
  make_ss (mss, subgoal_tac, loop_tacs, finish_tac, unsafe_finish_tac);

fun (Simpset {mss, subgoal_tac, loop_tacs, finish_tac, unsafe_finish_tac})
    addSolver tac =
  make_ss (mss, subgoal_tac, loop_tacs, finish_tac,
    fn hyps => unsafe_finish_tac hyps ORELSE' tac hyps);

fun (Simpset {mss, subgoal_tac, loop_tacs, finish_tac, unsafe_finish_tac})
    setmksimps mk_simps =
  make_ss (Thm.set_mk_rews (mss, map (Thm.strip_shyps o Drule.zero_var_indexes) o mk_simps),
    subgoal_tac, loop_tacs, finish_tac, unsafe_finish_tac);

fun (Simpset {mss, subgoal_tac, loop_tacs, finish_tac, unsafe_finish_tac})
    setmkeqTrue mk_eq_True =
  make_ss (Thm.set_mk_eq_True (mss, mk_eq_True),
    subgoal_tac, loop_tacs, finish_tac, unsafe_finish_tac);

fun (Simpset {mss, subgoal_tac, loop_tacs, finish_tac, unsafe_finish_tac})
    setmksym mksym =
  make_ss (Thm.set_mk_sym (mss, mksym),
    subgoal_tac, loop_tacs, finish_tac, unsafe_finish_tac);

fun (Simpset {mss, subgoal_tac, loop_tacs,  finish_tac, unsafe_finish_tac})
    settermless termless =
  make_ss (Thm.set_termless (mss, termless), subgoal_tac, loop_tacs,
    finish_tac, unsafe_finish_tac);

fun (Simpset {mss, subgoal_tac, loop_tacs, finish_tac, unsafe_finish_tac})
    addsimps rews =
  make_ss (Thm.add_simps (mss, rews), subgoal_tac, loop_tacs,
           finish_tac, unsafe_finish_tac);

fun (Simpset {mss, subgoal_tac, loop_tacs, finish_tac, unsafe_finish_tac})
    delsimps rews =
  make_ss (Thm.del_simps (mss, rews), subgoal_tac, loop_tacs,
           finish_tac, unsafe_finish_tac);

fun (Simpset {mss, subgoal_tac, loop_tacs, finish_tac, unsafe_finish_tac})
    addeqcongs newcongs =
  make_ss (Thm.add_congs (mss, newcongs), subgoal_tac, loop_tacs,
    finish_tac, unsafe_finish_tac);

fun (Simpset {mss, subgoal_tac, loop_tacs, finish_tac, unsafe_finish_tac})
    deleqcongs oldcongs =
  make_ss (Thm.del_congs (mss, oldcongs), subgoal_tac, loop_tacs,
    finish_tac, unsafe_finish_tac);

fun (Simpset {mss, subgoal_tac, loop_tacs, finish_tac, unsafe_finish_tac})
    addsimprocs simprocs =
  make_ss
    (Thm.add_simprocs (mss, map rep_simproc simprocs),
      subgoal_tac, loop_tacs, finish_tac, unsafe_finish_tac);

fun (Simpset {mss, subgoal_tac, loop_tacs, finish_tac, unsafe_finish_tac})
    delsimprocs simprocs =
  make_ss
    (Thm.del_simprocs (mss, map rep_simproc simprocs),
      subgoal_tac, loop_tacs, finish_tac, unsafe_finish_tac);


(* merge simpsets *)    (*NOTE: ignores tactics of 2nd simpset (except loopers)*)

fun merge_ss
   (Simpset {mss = mss1, loop_tacs = loop_tacs1, subgoal_tac, finish_tac, unsafe_finish_tac},
    Simpset {mss = mss2, loop_tacs = loop_tacs2, ...}) =
  make_ss (Thm.merge_mss (mss1, mss2), subgoal_tac,
    merge_alists loop_tacs1 loop_tacs2, finish_tac, unsafe_finish_tac);



(** global and local simpset data **)

(* theory data kind 'Provers/simpset' *)

structure GlobalSimpsetArgs =
struct
  val name = "Provers/simpset";
  type T = simpset ref;

  val empty = ref empty_ss;
  fun prep_ext (ref ss) = (ref ss): T;            (*create new reference!*)
  fun merge (ref ss1, ref ss2) = ref (merge_ss (ss1, ss2));
  fun print _ (ref ss) = print_ss ss;
end;

structure GlobalSimpset = TheoryDataFun(GlobalSimpsetArgs);
val print_simpset = GlobalSimpset.print;
val simpset_ref_of_sg = GlobalSimpset.get_sg;
val simpset_ref_of = GlobalSimpset.get;


(* access global simpset *)

val simpset_of_sg = ! o simpset_ref_of_sg;
val simpset_of = simpset_of_sg o sign_of;

fun SIMPSET tacf state = tacf (simpset_of_sg (sign_of_thm state)) state;
fun SIMPSET' tacf i state = tacf (simpset_of_sg (sign_of_thm state)) i state;

val simpset = simpset_of o Context.the_context;
val simpset_ref = simpset_ref_of_sg o sign_of o Context.the_context;


(* change global simpset *)

fun change_simpset f x = simpset_ref () := (f (simpset (), x));

val Addsimps = change_simpset (op addsimps);
val Delsimps = change_simpset (op delsimps);
val Addsimprocs = change_simpset (op addsimprocs);
val Delsimprocs = change_simpset (op delsimprocs);


(* proof data kind 'Provers/simpset' *)

structure LocalSimpsetArgs =
struct
  val name = "Provers/simpset";
  type T = simpset;
  val init = simpset_of;
  fun print _ ss = print_ss ss;
end;

structure LocalSimpset = ProofDataFun(LocalSimpsetArgs);
val print_local_simpset = LocalSimpset.print;
val get_local_simpset = LocalSimpset.get;
val put_local_simpset = LocalSimpset.put;


(* attributes *)

fun change_global_ss f (thy, th) =
  let val r = simpset_ref_of thy
  in r := f (! r, [Attribute.thm_of th]); (thy, th) end;

fun change_local_ss f (ctxt, th) =
  let val ss = f (get_local_simpset ctxt, [Attribute.thm_of th])
  in (put_local_simpset ss ctxt, th) end;

val simp_add_global = change_global_ss (op addsimps);
val simp_del_global = change_global_ss (op delsimps);
val simp_add_local = change_local_ss (op addsimps);
val simp_del_local = change_local_ss (op delsimps);



(** simplification tactics **)

fun solve_all_tac (subgoal_tac, loop_tacs, finish_tac, unsafe_finish_tac) mss =
  let
    val ss =
      make_ss (mss, subgoal_tac, loop_tacs, unsafe_finish_tac, unsafe_finish_tac);
    val solve1_tac = (subgoal_tac ss THEN_ALL_NEW (K no_tac)) 1
  in DEPTH_SOLVE solve1_tac end;

fun loop_tac loop_tacs = FIRST'(map snd loop_tacs);

(*not totally safe: may instantiate unknowns that appear also in other subgoals*)
fun basic_gen_simp_tac mode =
  fn (Simpset {mss, subgoal_tac, loop_tacs, finish_tac, unsafe_finish_tac}) =>
    let
      fun simp_loop_tac i =
        asm_rewrite_goal_tac mode
          (solve_all_tac (subgoal_tac,loop_tacs,finish_tac,unsafe_finish_tac))
          mss i
        THEN (finish_tac (prems_of_mss mss) i ORELSE
              TRY ((loop_tac loop_tacs THEN_ALL_NEW simp_loop_tac) i))
    in simp_loop_tac end;

fun gen_simp_tac mode (ss as Simpset {unsafe_finish_tac, ...}) =
  basic_gen_simp_tac mode (ss setSSolver unsafe_finish_tac);

val          simp_tac = gen_simp_tac (false, false, false);
val      asm_simp_tac = gen_simp_tac (false, true, false);
val     full_simp_tac = gen_simp_tac (true,  false, false);
val   asm_lr_simp_tac = gen_simp_tac (true,  true, false);
val asm_full_simp_tac = gen_simp_tac (true,  true, true);

(*not totally safe: may instantiate unknowns that appear also in other subgoals*)
val safe_asm_full_simp_tac = basic_gen_simp_tac (true, true, false);

(*the abstraction over the proof state delays the dereferencing*)
fun          Simp_tac i st =          simp_tac (simpset ()) i st;
fun      Asm_simp_tac i st =      asm_simp_tac (simpset ()) i st;
fun     Full_simp_tac i st =     full_simp_tac (simpset ()) i st;
fun   Asm_lr_simp_tac i st =   asm_lr_simp_tac (simpset ()) i st;
fun Asm_full_simp_tac i st = asm_full_simp_tac (simpset ()) i st;



(** simplification rules and conversions **)

fun simp rew mode (Simpset {mss, subgoal_tac, loop_tacs, finish_tac, unsafe_finish_tac}) thm =
  let
    val tacf = solve_all_tac (subgoal_tac, loop_tacs, finish_tac, unsafe_finish_tac);
    fun prover m th = apsome fst (Seq.pull (tacf m th));
  in rew mode prover mss thm end;

val simp_thm = simp Drule.rewrite_thm;
val simp_cterm = simp Drule.rewrite_cterm;

val          simplify = simp_thm (false, false, false);
val      asm_simplify = simp_thm (false, true, false);
val     full_simplify = simp_thm (true, false, false);
val asm_full_simplify = simp_thm (true, true, false);

val          rewrite = simp_cterm (false, false, false);
val      asm_rewrite = simp_cterm (false, true, false);
val     full_rewrite = simp_cterm (true, false, false);
val asm_full_rewrite = simp_cterm (true, true, false);



(** concrete syntax of attributes **)

(* add / del *)

val simpN = "simp";
val addN = "add";
val delN = "del";
val otherN = "other";

fun simp_att change =
  (Args.$$$ addN >> K (op addsimps) ||
    Args.$$$ delN >> K (op delsimps) ||
    Scan.succeed (op addsimps))
  >> change
  |> Scan.lift
  |> Attrib.syntax;

val simp_attr = (simp_att change_global_ss, simp_att change_local_ss);


(* conversions *)

fun conv_attr f =
  (Attrib.no_args (Attribute.rule (f o simpset_of)),
    Attrib.no_args (Attribute.rule (f o get_local_simpset)));


(* setup_attrs *)

val setup_attrs = Attrib.add_attributes
 [(simpN,               simp_attr, "simplification rule"),
  ("simplify",          conv_attr simplify, "simplify rule"),
  ("asm_simplify",      conv_attr asm_simplify, "simplify rule, using assumptions"),
  ("full_simplify",     conv_attr full_simplify, "fully simplify rule"),
  ("asm_full_simplify", conv_attr asm_full_simplify, "fully simplify rule, using assumptions")];



(** proof methods **)

(* simplification *)

val simp_modifiers =
 [Args.$$$ simpN -- Args.$$$ addN >> K simp_add_local,
  Args.$$$ simpN -- Args.$$$ delN >> K simp_del_local,
  Args.$$$ otherN >> K I];	(* FIXME ?? *)

val simp_modifiers' =
 [Args.$$$ addN >> K simp_add_local,
  Args.$$$ delN >> K simp_del_local,
  Args.$$$ otherN >> K I];

val simp_args = Method.only_sectioned_args simp_modifiers';

fun simp_meth tac ctxt = Method.METHOD (fn facts =>
  FIRSTGOAL (REPEAT_DETERM o etac Drule.thin_rl THEN'
    metacuts_tac (Attribute.thms_of facts) THEN'
    tac (get_local_simpset ctxt)));

val simp_method = simp_args o simp_meth;


(* setup_methods *)

val setup_methods = Method.add_methods
 [(simpN,               simp_method asm_full_simp_tac, "simplification"),
  ("simp_tac",          simp_method simp_tac, "simp_tac"),
  ("asm_simp_tac",      simp_method asm_simp_tac, "asm_simp_tac"),
  ("full_simp_tac",     simp_method full_simp_tac, "full_simp_tac"),
  ("asm_full_simp_tac", simp_method asm_full_simp_tac, "asm_full_simp_tac"),
  ("asm_lr_simp_tac",   simp_method asm_lr_simp_tac, "asm_lr_simp_tac")];



(** theory setup **)

val setup = [GlobalSimpset.init, LocalSimpset.init, setup_attrs, setup_methods];


end;


structure BasicSimplifier: BASIC_SIMPLIFIER = Simplifier;
open BasicSimplifier;