File ‹~~/src/Provers/order_tac.ML›

signature REIFY_TABLE =
sig
  type table
  val empty : table
  val get_var : term -> table -> (int * table)
  val get_term : int -> table -> term option
end

structure Reifytab: REIFY_TABLE =
struct
  type table = (int * (term * int) list)
  
  val empty = (0, [])
  
  fun get_var t (max_var, tis) =
    (case AList.lookup Envir.aeconv tis t of
      SOME v => (v, (max_var, tis))
    | NONE => (max_var, (max_var + 1, (t, max_var) :: tis))
    )
  
  fun get_term v (_, tis) = Library.find_first (fn (_, v2) => v = v2) tis
                            |> Option.map fst
end

signature LOGIC_SIGNATURE =
sig
  val mk_Trueprop : term -> term
  val dest_Trueprop : term -> term
  val Trueprop_conv : conv -> conv
  val Not : term
  val conj : term
  val disj : term
  
  val notI : thm (* (P ⟹ False) ⟹ ¬ P *)
  val ccontr : thm (* (¬ P ⟹ False) ⟹ P *)
  val conjI : thm (* P ⟹ Q ⟹ P ∧ Q *)
  val conjE : thm (* P ∧ Q ⟹ (P ⟹ Q ⟹ R) ⟹ R *)
  val disjE : thm (* P ∨ Q ⟹ (P ⟹ R) ⟹ (Q ⟹ R) ⟹ R *)

  val not_not_conv : conv (* ¬ (¬ P) ≡ P *)
  val de_Morgan_conj_conv : conv (* ¬ (P ∧ Q) ≡ ¬ P ∨ ¬ Q *)
  val de_Morgan_disj_conv : conv (* ¬ (P ∨ Q) ≡ ¬ P ∧ ¬ Q *)
  val conj_disj_distribL_conv : conv (* P ∧ (Q ∨ R) ≡ (P ∧ Q) ∨ (P ∧ R) *)
  val conj_disj_distribR_conv : conv (* (Q ∨ R) ∧ P ≡ (Q ∧ P) ∨ (R ∧ P) *)
end

(* Control tracing output of the solver. *)
val order_trace_cfg = Attrib.setup_config_bool @{binding "order_trace"} (K false)
(* In partial orders, literals of the form ¬ x < y will force the order solver to perform case
   distinctions, which leads to an exponential blowup of the runtime. The split limit controls
   the number of literals of this form that are passed to the solver. 
 *)
val order_split_limit_cfg = Attrib.setup_config_int @{binding "order_split_limit"} (K 8)

datatype order_kind = Order | Linorder

type order_literal = (bool * Order_Procedure.order_atom)

type order_context = {
    kind : order_kind,
    ops : term list, thms : (string * thm) list, conv_thms : (string * thm) list
  }

signature BASE_ORDER_TAC =
sig

  val tac :
        (order_literal Order_Procedure.fm -> Order_Procedure.prf_trm option)
        -> order_context -> thm list
        -> Proof.context -> int -> tactic
end

functor Base_Order_Tac(
  structure Logic_Sig : LOGIC_SIGNATURE; val excluded_types : typ list) : BASE_ORDER_TAC =
struct
  open Order_Procedure

  fun expect _ (SOME x) = x
    | expect f NONE = f ()

  fun list_curry0 f = (fn [] => f, 0)
  fun list_curry1 f = (fn [x] => f x, 1)
  fun list_curry2 f = (fn [x, y] => f x y, 2)

  fun dereify_term consts reifytab t =
    let
      fun dereify_term' (App (t1, t2)) = (dereify_term' t1) $ (dereify_term' t2)
        | dereify_term' (Const s) =
            AList.lookup (op =) consts s
            |> expect (fn () => raise TERM ("Const " ^ s ^ " not in", map snd consts))
        | dereify_term' (Var v) = Reifytab.get_term (integer_of_int v) reifytab |> the
    in
      dereify_term' t
    end

  fun dereify_order_fm (eq, le, lt) reifytab t =
    let
      val consts = [
        ("eq", eq), ("le", le), ("lt", lt),
        ("Not", Logic_Sig.Not), ("disj", Logic_Sig.disj), ("conj", Logic_Sig.conj)
        ]
    in
      dereify_term consts reifytab t
    end

  fun strip_AppP t =
    let fun strip (AppP (f, s), ss) = strip (f, s::ss)
          | strip x = x
    in strip (t, []) end

  fun replay_conv convs cvp =
    let
      val convs = convs @
        [("all_conv", list_curry0 Conv.all_conv)] @ 
        map (apsnd list_curry1) [
          ("atom_conv", I),
          ("neg_atom_conv", I),
          ("arg_conv", Conv.arg_conv)] @
        map (apsnd list_curry2) [
          ("combination_conv", Conv.combination_conv),
          ("then_conv", curry (op then_conv))]

      fun lookup_conv convs c = AList.lookup (op =) convs c
            |> expect (fn () => error ("Can't replay conversion: " ^ c))

      fun rp_conv t =
        (case strip_AppP t ||> map rp_conv of
          (PThm c, cvs) =>
            let val (conv, arity) = lookup_conv convs c
            in if arity = length cvs
              then conv cvs
              else error ("Expected " ^ Int.toString arity ^ " arguments for conversion " ^
                          c ^ " but got " ^ (length cvs |> Int.toString) ^ " arguments")
            end
        | _ => error "Unexpected constructor in conversion proof")
    in
      rp_conv cvp
    end

  fun replay_prf_trm replay_conv dereify ctxt thmtab assmtab p =
    let
      fun replay_prf_trm' _ (PThm s) =
            AList.lookup (op =) thmtab s
            |> expect (fn () => error ("Cannot replay theorem: " ^ s))
        | replay_prf_trm' assmtab (Appt (p, t)) =
            replay_prf_trm' assmtab p
            |> Drule.infer_instantiate' ctxt [SOME (Thm.cterm_of ctxt (dereify t))]
        | replay_prf_trm' assmtab (AppP (p1, p2)) =
            apply2 (replay_prf_trm' assmtab) (p2, p1) |> op COMP
        | replay_prf_trm' assmtab (AbsP (reified_t, p)) =
            let
              val t = dereify reified_t
              val t_thm = Logic_Sig.mk_Trueprop t |> Thm.cterm_of ctxt |> Assumption.assume ctxt
              val rp = replay_prf_trm' (Termtab.update (Thm.prop_of t_thm, t_thm) assmtab) p
            in
              Thm.implies_intr (Thm.cprop_of t_thm) rp
            end
        | replay_prf_trm' assmtab (Bound reified_t) =
            let
              val t = dereify reified_t |> Logic_Sig.mk_Trueprop
            in
              Termtab.lookup assmtab t
              |> expect (fn () => raise TERM ("Assumption not found:", t::Termtab.keys assmtab))
            end
        | replay_prf_trm' assmtab (Conv (t, cp, p)) =
            let
              val thm = replay_prf_trm' assmtab (Bound t)
              val conv = Logic_Sig.Trueprop_conv (replay_conv cp)
              val conv_thm = Conv.fconv_rule conv thm
              val conv_term = Thm.prop_of conv_thm
            in
              replay_prf_trm' (Termtab.update (conv_term, conv_thm) assmtab) p
            end
    in
      replay_prf_trm' assmtab p
    end

  fun replay_order_prf_trm ord_ops {thms = thms, conv_thms = conv_thms, ...} ctxt reifytab assmtab =
    let
      val thmtab = thms @ [
          ("conjE", Logic_Sig.conjE), ("conjI", Logic_Sig.conjI), ("disjE", Logic_Sig.disjE)
        ]
      val convs = map (apsnd list_curry0) (
        map (apsnd Conv.rewr_conv) conv_thms @
        [
          ("not_not_conv", Logic_Sig.not_not_conv),
          ("de_Morgan_conj_conv", Logic_Sig.de_Morgan_conj_conv),
          ("de_Morgan_disj_conv", Logic_Sig.de_Morgan_disj_conv),
          ("conj_disj_distribR_conv", Logic_Sig.conj_disj_distribR_conv),
          ("conj_disj_distribL_conv", Logic_Sig.conj_disj_distribL_conv)
        ])
      
      val dereify = dereify_order_fm ord_ops reifytab
    in
      replay_prf_trm (replay_conv convs) dereify ctxt thmtab assmtab
    end

  fun strip_Not (nt $ t) = if nt = Logic_Sig.Not then t else nt $ t
    | strip_Not t = t

  fun limit_not_less [_, _, lt] ctxt decomp_prems =
    let
      val thy = Proof_Context.theory_of ctxt
      val trace = Config.get ctxt order_trace_cfg
      val limit = Config.get ctxt order_split_limit_cfg

      fun is_not_less_term t =
        case try (strip_Not o Logic_Sig.dest_Trueprop) t of
          SOME (binop $ _ $ _) => Pattern.matches thy (lt, binop)
        | NONE => false

      val not_less_prems = filter (is_not_less_term o Thm.prop_of o fst) decomp_prems
      val _ = if trace andalso length not_less_prems > limit
                then tracing "order split limit exceeded"
                else ()
     in
      filter_out (is_not_less_term o Thm.prop_of o fst) decomp_prems @
      take limit not_less_prems
     end

  fun decomp [eq, le, lt] ctxt t =
    let
      fun is_excluded t = exists (fn ty => ty = fastype_of t) excluded_types

      fun decomp'' (binop $ t1 $ t2) =
            let
              open Order_Procedure
              val thy = Proof_Context.theory_of ctxt
              fun try_match pat = try (Pattern.match thy (pat, binop)) (Vartab.empty, Vartab.empty)
            in if is_excluded t1 then NONE
               else case (try_match eq, try_match le, try_match lt) of
                      (SOME env, _, _) => SOME (true, EQ, (t1, t2), env)
                    | (_, SOME env, _) => SOME (true, LEQ, (t1, t2), env)
                    | (_, _, SOME env) => SOME (true, LESS, (t1, t2), env)
                    | _ => NONE
            end
        | decomp'' _ = NONE

        fun decomp' (nt $ t) =
              if nt = Logic_Sig.Not
                then decomp'' t |> Option.map (fn (b, c, p, e) => (not b, c, p, e))
                else decomp'' (nt $ t)
          | decomp' t = decomp'' t

    in
      try Logic_Sig.dest_Trueprop t |> Option.mapPartial decomp'
    end

  fun maximal_envs envs =
    let
      fun test_opt p (SOME x) = p x
        | test_opt _ NONE = false

      fun leq_env (tyenv1, tenv1) (tyenv2, tenv2) =
        Vartab.forall (fn (v, ty) =>
          Vartab.lookup tyenv2 v |> test_opt (fn ty2 => ty2 = ty)) tyenv1
        andalso
        Vartab.forall (fn (v, (ty, t)) =>
          Vartab.lookup tenv2 v |> test_opt (fn (ty2, t2) => ty2 = ty andalso t2 aconv t)) tenv1

      fun fold_env (i, env) es = fold_index (fn (i2, env2) => fn es =>
        if i = i2 then es else if leq_env env env2 then (i, i2) :: es else es) envs es
      
      val env_order = fold_index fold_env envs []

      val graph = fold_index (fn (i, env) => fn g => Int_Graph.new_node (i, env) g)
                             envs Int_Graph.empty
      val graph = fold Int_Graph.add_edge env_order graph

      val strong_conns = Int_Graph.strong_conn graph
      val maximals =
        filter (fn comp => length comp = length (Int_Graph.all_succs graph comp)) strong_conns
    in
      map (Int_Graph.all_preds graph) maximals
    end
      
  fun order_tac raw_order_proc octxt simp_prems =
    Subgoal.FOCUS (fn {prems=prems, context=ctxt, ...} =>
      let
        val trace = Config.get ctxt order_trace_cfg

        fun these' _ [] = []
          | these' f (x :: xs) = case f x of NONE => these' f xs | SOME y => (x, y) :: these' f xs

        val prems = simp_prems @ prems
                    |> filter (fn p => null (Term.add_vars (Thm.prop_of p) []))
                    |> map (Conv.fconv_rule Thm.eta_conversion)
        val decomp_prems = these' (decomp (#ops octxt) ctxt o Thm.prop_of) prems

        fun env_of (_, (_, _, _, env)) = env
        val env_groups = maximal_envs (map env_of decomp_prems)
        
        fun order_tac' (_, []) = no_tac
          | order_tac' (env, decomp_prems) =
            let
              val [eq, le, lt] = #ops octxt |> map (Envir.eta_contract o Envir.subst_term env)

              val decomp_prems = case #kind octxt of
                                   Order => limit_not_less (#ops octxt) ctxt decomp_prems
                                 | _ => decomp_prems
      
              fun reify_prem (_, (b, ctor, (x, y), _)) (ps, reifytab) =
                (Reifytab.get_var x ##>> Reifytab.get_var y) reifytab
                |>> (fn vp => (b, ctor (apply2 Int_of_integer vp)) :: ps)
              val (reified_prems, reifytab) = fold_rev reify_prem decomp_prems ([], Reifytab.empty)

              val reified_prems_conj = foldl1 (fn (x, a) => And (x, a)) (map Atom reified_prems)
              val prems_conj_thm = map fst decomp_prems
                                   |> foldl1 (fn (x, a) => Logic_Sig.conjI OF [x, a])
                                   |> Conv.fconv_rule Thm.eta_conversion 
              val prems_conj = prems_conj_thm |> Thm.prop_of
              
              val proof = raw_order_proc reified_prems_conj

              val pretty_term_list =
                Pretty.list "" "" o map (Syntax.pretty_term (Config.put show_types true ctxt))
              val pretty_thm_list = Pretty.list "" "" o map (Thm.pretty_thm ctxt)
              fun pretty_type_of t = Pretty.block [ Pretty.str "::", Pretty.brk 1,
                    Pretty.quote (Syntax.pretty_typ ctxt (Term.fastype_of t)) ]
              fun pretty_trace () = 
                [ ("order kind:", Pretty.str (@{make_string} (#kind octxt)))
                , ("order operators:", Pretty.block [ pretty_term_list [eq, le, lt], Pretty.brk 1
                                                     , pretty_type_of le ])
                , ("premises:", pretty_thm_list prems)
                , ("selected premises:", pretty_thm_list (map fst decomp_prems))
                , ("reified premises:", Pretty.str (@{make_string} reified_prems))
                , ("contradiction:", Pretty.str (@{make_string} (Option.isSome proof)))
                ] |> map (fn (t, pp) => Pretty.block [Pretty.str t, Pretty.brk 1, pp])
                  |> Pretty.big_list "order solver called with the parameters"
              val _ = if trace then tracing (Pretty.string_of (pretty_trace ())) else ()

              val assmtab = Termtab.make [(prems_conj, prems_conj_thm)]
              val replay = replay_order_prf_trm (eq, le, lt) octxt ctxt reifytab assmtab
            in
              case proof of
                NONE => no_tac
              | SOME p => SOLVED' (resolve_tac ctxt [replay p]) 1
            end
     in
       map (fn is => ` (env_of o hd) (map (nth decomp_prems) is) |> order_tac') env_groups
       |> FIRST
     end)

  val ad_absurdum_tac = SUBGOAL (fn (A, i) =>
    case try (Logic_Sig.dest_Trueprop o Logic.strip_assums_concl) A of
      SOME (nt $ _) =>
        if nt = Logic_Sig.Not
          then resolve0_tac [Logic_Sig.notI] i
          else resolve0_tac [Logic_Sig.ccontr] i
    | _ => resolve0_tac [Logic_Sig.ccontr] i)

  fun tac raw_order_proc octxt simp_prems ctxt =
    ad_absurdum_tac THEN' order_tac raw_order_proc octxt simp_prems ctxt
  
end

functor Order_Tac(structure Base_Tac : BASE_ORDER_TAC) = struct

  fun order_context_eq ({kind = kind1, ops = ops1, ...}, {kind = kind2, ops = ops2, ...}) =
    kind1 = kind2 andalso eq_list (op aconv) (ops1, ops2)

  fun order_data_eq (x, y) = order_context_eq (fst x, fst y)
  
  structure Data = Generic_Data(
    type T = (order_context * (order_context -> thm list -> Proof.context -> int -> tactic)) list
    val empty = []
    fun merge data = Library.merge order_data_eq data
  )

  fun declare (octxt as {kind = kind, raw_proc = raw_proc, ...}) lthy =
    lthy |> Local_Theory.declaration {syntax = false, pervasive = false} (fn phi => fn context =>
      let
        val ops = map (Morphism.term phi) (#ops octxt)
        val thms = map (fn (s, thm) => (s, Morphism.thm phi thm)) (#thms octxt)
        val conv_thms = map (fn (s, thm) => (s, Morphism.thm phi thm)) (#conv_thms octxt)
        val octxt' = {kind = kind, ops = ops, thms = thms, conv_thms = conv_thms}
      in
        context |> Data.map (Library.insert order_data_eq (octxt', raw_proc))
      end)

  fun declare_order {
      ops = {eq = eq, le = le, lt = lt},
      thms = {
        trans = trans, (* x ≤ y ⟹ y ≤ z ⟹ x ≤ z *)
        refl = refl, (* x ≤ x *)
        eqD1 = eqD1, (* x = y ⟹ x ≤ y *)
        eqD2 = eqD2, (* x = y ⟹ y ≤ x *)
        antisym = antisym, (* x ≤ y ⟹ y ≤ x ⟹ x = y *)
        contr = contr (* ¬ P ⟹ P ⟹ R *)
      },
      conv_thms = {
        less_le = less_le, (* x < y ≡ x ≤ y ∧ x ≠ y *)
        nless_le = nless_le (* ¬ a < b ≡ ¬ a ≤ b ∨ a = b *)
      }
    } =
    declare {
      kind = Order,
      ops = [eq, le, lt],
      thms = [("trans", trans), ("refl", refl), ("eqD1", eqD1), ("eqD2", eqD2),
              ("antisym", antisym), ("contr", contr)],
      conv_thms = [("less_le", less_le), ("nless_le", nless_le)],
      raw_proc = Base_Tac.tac Order_Procedure.po_contr_prf
     }                

  fun declare_linorder {
      ops = {eq = eq, le = le, lt = lt},
      thms = {
        trans = trans, (* x ≤ y ⟹ y ≤ z ⟹ x ≤ z *)
        refl = refl, (* x ≤ x *)
        eqD1 = eqD1, (* x = y ⟹ x ≤ y *)
        eqD2 = eqD2, (* x = y ⟹ y ≤ x *)
        antisym = antisym, (* x ≤ y ⟹ y ≤ x ⟹ x = y *)
        contr = contr (* ¬ P ⟹ P ⟹ R *)
      },
      conv_thms = {
        less_le = less_le, (* x < y ≡ x ≤ y ∧ x ≠ y *)
        nless_le = nless_le, (* ¬ x < y ≡ y ≤ x *)
        nle_le = nle_le (* ¬ a ≤ b ≡ b ≤ a ∧ b ≠ a *)
      }
    } =
    declare {
      kind = Linorder,
      ops = [eq, le, lt],
      thms = [("trans", trans), ("refl", refl), ("eqD1", eqD1), ("eqD2", eqD2),
              ("antisym", antisym), ("contr", contr)],
      conv_thms = [("less_le", less_le), ("nless_le", nless_le), ("nle_le", nle_le)],
      raw_proc = Base_Tac.tac Order_Procedure.lo_contr_prf
     }
  
  (* Try to solve the goal by calling the order solver with each of the declared orders. *)      
  fun tac simp_prems ctxt =
    let fun app_tac (octxt, tac0) = CHANGED o tac0 octxt simp_prems ctxt
    in FIRST' (map app_tac (Data.get (Context.Proof ctxt))) end
end