src/Pure/Isar/element.ML

Method.Basic: no position;

(*  Title:      Pure/Isar/element.ML
    Author:     Makarius

Explicit data structures for some Isar language elements, with derived
logical operations.
*)

signature ELEMENT =
sig
  datatype ('typ, 'term) stmt =
    Shows of (Attrib.binding * ('term * 'term list) list) list |
    Obtains of (binding * ((binding * 'typ option) list * 'term list)) list
  type statement = (string, string) stmt
  type statement_i = (typ, term) stmt
  datatype ('typ, 'term, 'fact) ctxt =
    Fixes of (binding * 'typ option * mixfix) list |
    Constrains of (string * 'typ) list |
    Assumes of (Attrib.binding * ('term * 'term list) list) list |
    Defines of (Attrib.binding * ('term * 'term list)) list |
    Notes of string * (Attrib.binding * ('fact * Attrib.src list) list) list
  type context = (string, string, Facts.ref) ctxt
  type context_i = (typ, term, thm list) ctxt
  val facts_map: (('typ, 'term, 'fact) ctxt -> ('a, 'b, 'c) ctxt) ->
   (Attrib.binding * ('fact * Attrib.src list) list) list ->
   (Attrib.binding * ('c * Attrib.src list) list) list
  val map_ctxt: {binding: binding -> binding, typ: 'typ -> 'a, term: 'term -> 'b,
    pattern: 'term -> 'b, fact: 'fact -> 'c, attrib: Attrib.src -> Attrib.src} ->
    ('typ, 'term, 'fact) ctxt -> ('a, 'b, 'c) ctxt
  val map_ctxt_attrib: (Attrib.src -> Attrib.src) ->
    ('typ, 'term, 'fact) ctxt -> ('typ, 'term, 'fact) ctxt
  val morph_ctxt: morphism -> context_i -> context_i
  val pretty_stmt: Proof.context -> statement_i -> Pretty.T list
  val pretty_ctxt: Proof.context -> context_i -> Pretty.T list
  val pretty_statement: Proof.context -> string -> thm -> Pretty.T
  type witness
  val prove_witness: Proof.context -> term -> tactic -> witness
  val witness_proof: (witness list list -> Proof.context -> Proof.context) ->
    term list list -> Proof.context -> Proof.state
  val witness_proof_eqs: (witness list list -> thm list -> Proof.context -> Proof.context) ->
    term list list -> term list -> Proof.context -> Proof.state
  val witness_local_proof: (witness list list -> Proof.state -> Proof.state) ->
    string -> term list list -> Proof.context -> bool -> Proof.state -> Proof.state
  val morph_witness: morphism -> witness -> witness
  val conclude_witness: witness -> thm
  val pretty_witness: Proof.context -> witness -> Pretty.T
  val instT_type: typ Symtab.table -> typ -> typ
  val instT_term: typ Symtab.table -> term -> term
  val instT_thm: theory -> typ Symtab.table -> thm -> thm
  val instT_morphism: theory -> typ Symtab.table -> morphism
  val inst_term: typ Symtab.table * term Symtab.table -> term -> term
  val inst_thm: theory -> typ Symtab.table * term Symtab.table -> thm -> thm
  val inst_morphism: theory -> typ Symtab.table * term Symtab.table -> morphism
  val satisfy_thm: witness list -> thm -> thm
  val satisfy_morphism: witness list -> morphism
  val satisfy_facts: witness list ->
    (Attrib.binding * (thm list * Attrib.src list) list) list ->
    (Attrib.binding * (thm list * Attrib.src list) list) list
  val generalize_facts: Proof.context -> Proof.context ->
    (Attrib.binding * (thm list * Attrib.src list) list) list ->
    (Attrib.binding * (thm list * Attrib.src list) list) list
  val eq_morphism: theory -> thm list -> morphism
  val transfer_morphism: theory -> morphism
  val init: context_i -> Context.generic -> Context.generic
  val activate_i: context_i -> Proof.context -> context_i * Proof.context
  val activate: (typ, term, Facts.ref) ctxt -> Proof.context -> context_i * Proof.context
end;

structure Element: ELEMENT =
struct

(** language elements **)

(* statement *)

datatype ('typ, 'term) stmt =
  Shows of (Attrib.binding * ('term * 'term list) list) list |
  Obtains of (binding * ((binding * 'typ option) list * 'term list)) list;

type statement = (string, string) stmt;
type statement_i = (typ, term) stmt;


(* context *)

datatype ('typ, 'term, 'fact) ctxt =
  Fixes of (binding * 'typ option * mixfix) list |
  Constrains of (string * 'typ) list |
  Assumes of (Attrib.binding * ('term * 'term list) list) list |
  Defines of (Attrib.binding * ('term * 'term list)) list |
  Notes of string * (Attrib.binding * ('fact * Attrib.src list) list) list;

type context = (string, string, Facts.ref) ctxt;
type context_i = (typ, term, thm list) ctxt;

fun facts_map f facts = Notes ("", facts) |> f |> (fn Notes (_, facts') => facts');

fun map_ctxt {binding, typ, term, pattern, fact, attrib} =
  fn Fixes fixes => Fixes (fixes |> map (fn (x, T, mx) => (binding x, Option.map typ T, mx)))
   | Constrains xs => Constrains (xs |> map (fn (x, T) =>
      (Name.of_binding (binding (Binding.name x)), typ T)))
   | Assumes asms => Assumes (asms |> map (fn ((a, atts), propps) =>
      ((binding a, map attrib atts), propps |> map (fn (t, ps) => (term t, map pattern ps)))))
   | Defines defs => Defines (defs |> map (fn ((a, atts), (t, ps)) =>
      ((binding a, map attrib atts), (term t, map pattern ps))))
   | Notes (kind, facts) => Notes (kind, facts |> map (fn ((a, atts), bs) =>
      ((binding a, map attrib atts), bs |> map (fn (ths, btts) => (fact ths, map attrib btts)))));

fun map_ctxt_attrib attrib =
  map_ctxt {binding = I, typ = I, term = I, pattern = I, fact = I, attrib = attrib};

fun morph_ctxt phi = map_ctxt
 {binding = Morphism.binding phi,
  typ = Morphism.typ phi,
  term = Morphism.term phi,
  pattern = Morphism.term phi,
  fact = Morphism.fact phi,
  attrib = Args.morph_values phi};



(** pretty printing **)

fun pretty_items _ _ [] = []
  | pretty_items keyword sep (x :: ys) =
      Pretty.block [Pretty.keyword keyword, Pretty.brk 1, x] ::
        map (fn y => Pretty.block [Pretty.str "  ", Pretty.keyword sep, Pretty.brk 1, y]) ys;

fun pretty_name_atts ctxt (b, atts) sep =
  if Binding.is_empty b andalso null atts then []
  else [Pretty.block (Pretty.breaks
    (Pretty.str (Binding.str_of b) :: Attrib.pretty_attribs ctxt atts @ [Pretty.str sep]))];


(* pretty_stmt *)

fun pretty_stmt ctxt =
  let
    val prt_typ = Pretty.quote o Syntax.pretty_typ ctxt;
    val prt_term = Pretty.quote o Syntax.pretty_term ctxt;
    val prt_terms = separate (Pretty.keyword "and") o map prt_term;
    val prt_name_atts = pretty_name_atts ctxt;

    fun prt_show (a, ts) =
      Pretty.block (Pretty.breaks (prt_name_atts a ":" @ prt_terms (map fst ts)));

    fun prt_var (x, SOME T) = Pretty.block
          [Pretty.str (Binding.name_of x ^ " ::"), Pretty.brk 1, prt_typ T]
      | prt_var (x, NONE) = Pretty.str (Binding.name_of x);
    val prt_vars = separate (Pretty.keyword "and") o map prt_var;

    fun prt_obtain (_, ([], ts)) = Pretty.block (Pretty.breaks (prt_terms ts))
      | prt_obtain (_, (xs, ts)) = Pretty.block (Pretty.breaks
          (prt_vars xs @ [Pretty.keyword "where"] @ prt_terms ts));
  in
    fn Shows shows => pretty_items "shows" "and" (map prt_show shows)
     | Obtains obtains => pretty_items "obtains" "|" (map prt_obtain obtains)
  end;


(* pretty_ctxt *)

fun pretty_ctxt ctxt =
  let
    val prt_typ = Pretty.quote o Syntax.pretty_typ ctxt;
    val prt_term = Pretty.quote o Syntax.pretty_term ctxt;
    val prt_thm = Pretty.backquote o Display.pretty_thm ctxt;
    val prt_name_atts = pretty_name_atts ctxt;

    fun prt_mixfix NoSyn = []
      | prt_mixfix mx = [Pretty.brk 2, Syntax.pretty_mixfix mx];

    fun prt_fix (x, SOME T, mx) = Pretty.block (Pretty.str (Binding.name_of x ^ " ::") ::
          Pretty.brk 1 :: prt_typ T :: Pretty.brk 1 :: prt_mixfix mx)
      | prt_fix (x, NONE, mx) = Pretty.block (Pretty.str (Binding.name_of x) ::
          Pretty.brk 1 :: prt_mixfix mx);
    fun prt_constrain (x, T) = prt_fix (Binding.name x, SOME T, NoSyn);

    fun prt_asm (a, ts) =
      Pretty.block (Pretty.breaks (prt_name_atts a ":" @ map (prt_term o fst) ts));
    fun prt_def (a, (t, _)) =
      Pretty.block (Pretty.breaks (prt_name_atts a ":" @ [prt_term t]));

    fun prt_fact (ths, []) = map prt_thm ths
      | prt_fact (ths, atts) = Pretty.enclose "(" ")"
          (Pretty.breaks (map prt_thm ths)) :: Attrib.pretty_attribs ctxt atts;
    fun prt_note (a, ths) =
      Pretty.block (Pretty.breaks (flat (prt_name_atts a "=" :: map prt_fact ths)));
  in
    fn Fixes fixes => pretty_items "fixes" "and" (map prt_fix fixes)
     | Constrains xs => pretty_items "constrains" "and" (map prt_constrain xs)
     | Assumes asms => pretty_items "assumes" "and" (map prt_asm asms)
     | Defines defs => pretty_items "defines" "and" (map prt_def defs)
     | Notes ("", facts) => pretty_items "notes" "and" (map prt_note facts)
     | Notes (kind, facts) => pretty_items ("notes " ^ kind) "and" (map prt_note facts)
  end;


(* pretty_statement *)

local

fun thm_name kind th prts =
  let val head =
    if Thm.has_name_hint th then
      Pretty.block [Pretty.command kind,
        Pretty.brk 1, Pretty.str (Long_Name.base_name (Thm.get_name_hint th) ^ ":")]
    else Pretty.command kind
  in Pretty.block (Pretty.fbreaks (head :: prts)) end;

fun fix (x, T) = (Binding.name x, SOME T);

fun obtain prop ctxt =
  let
    val ((xs, prop'), ctxt') = Variable.focus prop ctxt;
    val As = Logic.strip_imp_prems (Thm.term_of prop');
  in ((Binding.empty, (map (fix o Term.dest_Free o Thm.term_of) xs, As)), ctxt') end;

in

fun pretty_statement ctxt kind raw_th =
  let
    val thy = ProofContext.theory_of ctxt;
    val cert = Thm.cterm_of thy;

    val th = MetaSimplifier.norm_hhf raw_th;
    val is_elim = ObjectLogic.is_elim th;

    val ((_, [th']), ctxt') = Variable.import true [th] (Variable.set_body false ctxt);
    val prop = Thm.prop_of th';
    val (prems, concl) = Logic.strip_horn prop;
    val concl_term = ObjectLogic.drop_judgment thy concl;

    val fixes = fold_aterms (fn v as Free (x, T) =>
        if Variable.newly_fixed ctxt' ctxt x andalso not (v aconv concl_term)
        then insert (op =) (x, T) else I | _ => I) prop [] |> rev;
    val (assumes, cases) = take_suffix (fn prem =>
      is_elim andalso concl aconv Logic.strip_assums_concl prem) prems;
  in
    pretty_ctxt ctxt' (Fixes (map (fn (x, T) => (Binding.name x, SOME T, NoSyn)) fixes)) @
    pretty_ctxt ctxt' (Assumes (map (fn t => (Attrib.empty_binding, [(t, [])])) assumes)) @
     (if null cases then pretty_stmt ctxt' (Shows [(Attrib.empty_binding, [(concl, [])])])
      else
        let val (clauses, ctxt'') = fold_map (obtain o cert) cases ctxt'
        in pretty_stmt ctxt'' (Obtains clauses) end)
  end |> thm_name kind raw_th;

end;



(** logical operations **)

(* witnesses -- hypotheses as protected facts *)

datatype witness = Witness of term * thm;

val mark_witness = Logic.protect;
fun witness_prop (Witness (t, _)) = t;
fun witness_hyps (Witness (_, th)) = #hyps (Thm.rep_thm th);
fun map_witness f (Witness witn) = Witness (f witn);

fun morph_witness phi = map_witness (fn (t, th) => (Morphism.term phi t, Morphism.thm phi th));

fun prove_witness ctxt t tac =
  Witness (t, Thm.close_derivation (Goal.prove ctxt [] [] (mark_witness t) (fn _ =>
    Tactic.rtac Drule.protectI 1 THEN tac)));


local

val refine_witness =
  Proof.refine (Method.Basic (K (RAW_METHOD
    (K (ALLGOALS
      (CONJUNCTS (ALLGOALS
        (CONJUNCTS (TRYALL (Tactic.rtac Drule.protectI))))))))));

fun gen_witness_proof proof after_qed wit_propss eq_props =
  let
    val propss = (map o map) (fn prop => (mark_witness prop, [])) wit_propss
      @ [map (rpair []) eq_props];
    fun after_qed' thmss =
      let val (wits, eqs) = split_last ((map o map) Thm.close_derivation thmss);
      in after_qed ((map2 o map2) (curry Witness) wit_propss wits) eqs end;
  in proof after_qed' propss #> refine_witness #> Seq.hd end;

in

fun witness_proof after_qed wit_propss =
  gen_witness_proof (Proof.theorem_i NONE) (fn wits => fn _ => after_qed wits)
    wit_propss [];

val witness_proof_eqs = gen_witness_proof (Proof.theorem_i NONE);

fun witness_local_proof after_qed cmd wit_propss goal_ctxt int =
  gen_witness_proof (fn after_qed' => fn propss =>
    Proof.map_context (K goal_ctxt)
    #> Proof.local_goal (ProofDisplay.print_results int) (K I) ProofContext.bind_propp_i
      cmd NONE after_qed' (map (pair Thm.empty_binding) propss))
    (fn wits => fn _ => after_qed wits) wit_propss [];

end;


fun compose_witness (Witness (_, th)) r =
  let
    val th' = Goal.conclude th;
    val A = Thm.cprem_of r 1;
  in
    Thm.implies_elim
      (Conv.gconv_rule Drule.beta_eta_conversion 1 r)
      (Conv.fconv_rule Drule.beta_eta_conversion
        (Thm.instantiate (Thm.match (Thm.cprop_of th', A)) th'))
  end;

fun conclude_witness (Witness (_, th)) =
  Thm.close_derivation (MetaSimplifier.norm_hhf_protect (Goal.conclude th));

fun pretty_witness ctxt witn =
  let val prt_term = Pretty.quote o Syntax.pretty_term ctxt in
    Pretty.block (prt_term (witness_prop witn) ::
      (if ! show_hyps then [Pretty.brk 2, Pretty.list "[" "]"
         (map prt_term (witness_hyps witn))] else []))
  end;


(* derived rules *)

fun instantiate_tfrees thy subst th =
  let
    val certT = Thm.ctyp_of thy;
    val idx = Thm.maxidx_of th + 1;
    fun cert_inst (a, (S, T)) = (certT (TVar ((a, idx), S)), certT T);

    fun add_inst (a, S) insts =
      if AList.defined (op =) insts a then insts
      else (case AList.lookup (op =) subst a of NONE => insts | SOME T => (a, (S, T)) :: insts);
    val insts =
      Term.fold_types (Term.fold_atyps (fn TFree v => add_inst v | _ => I))
        (Thm.full_prop_of th) [];
  in
    th
    |> Thm.generalize (map fst insts, []) idx
    |> Thm.instantiate (map cert_inst insts, [])
  end;

fun instantiate_frees thy subst =
  let val cert = Thm.cterm_of thy in
    Drule.forall_intr_list (map (cert o Free o fst) subst) #>
    Drule.forall_elim_list (map (cert o snd) subst)
  end;

fun hyps_rule rule th =
  let val {hyps, ...} = Thm.crep_thm th in
    Drule.implies_elim_list
      (rule (Drule.implies_intr_list hyps th))
      (map (Thm.assume o Drule.cterm_rule rule) hyps)
  end;


(* instantiate types *)

fun instT_type env =
  if Symtab.is_empty env then I
  else Term.map_type_tfree (fn (x, S) => the_default (TFree (x, S)) (Symtab.lookup env x));

fun instT_term env =
  if Symtab.is_empty env then I
  else Term.map_types (instT_type env);

fun instT_subst env th = (Thm.fold_terms o Term.fold_types o Term.fold_atyps)
  (fn T as TFree (a, _) =>
    let val T' = the_default T (Symtab.lookup env a)
    in if T = T' then I else insert (op =) (a, T') end
  | _ => I) th [];

fun instT_thm thy env th =
  if Symtab.is_empty env then th
  else
    let val subst = instT_subst env th
    in if null subst then th else th |> hyps_rule (instantiate_tfrees thy subst) end;

fun instT_morphism thy env =
  let val thy_ref = Theory.check_thy thy in
    Morphism.morphism
     {binding = I,
      typ = instT_type env,
      term = instT_term env,
      fact = map (fn th => instT_thm (Theory.deref thy_ref) env th)}
  end;


(* instantiate types and terms *)

fun inst_term (envT, env) =
  if Symtab.is_empty env then instT_term envT
  else
    let
      val instT = instT_type envT;
      fun inst (Const (x, T)) = Const (x, instT T)
        | inst (Free (x, T)) =
            (case Symtab.lookup env x of
              NONE => Free (x, instT T)
            | SOME t => t)
        | inst (Var (xi, T)) = Var (xi, instT T)
        | inst (b as Bound _) = b
        | inst (Abs (x, T, t)) = Abs (x, instT T, inst t)
        | inst (t $ u) = inst t $ inst u;
    in Envir.beta_norm o inst end;

fun inst_thm thy (envT, env) th =
  if Symtab.is_empty env then instT_thm thy envT th
  else
    let
      val substT = instT_subst envT th;
      val subst = (Thm.fold_terms o Term.fold_aterms)
       (fn Free (x, T) =>
          let
            val T' = instT_type envT T;
            val t = Free (x, T');
            val t' = the_default t (Symtab.lookup env x);
          in if t aconv t' then I else insert (eq_fst (op =)) ((x, T'), t') end
       | _ => I) th [];
    in
      if null substT andalso null subst then th
      else th |> hyps_rule
       (instantiate_tfrees thy substT #>
        instantiate_frees thy subst #>
        Conv.fconv_rule (Thm.beta_conversion true))
    end;

fun inst_morphism thy envs =
  let val thy_ref = Theory.check_thy thy in
    Morphism.morphism
     {binding = I,
      typ = instT_type (#1 envs),
      term = inst_term envs,
      fact = map (fn th => inst_thm (Theory.deref thy_ref) envs th)}
  end;


(* satisfy hypotheses *)

fun satisfy_thm witns thm = thm |> fold (fn hyp =>
    (case find_first (fn Witness (t, _) => Thm.term_of hyp aconv t) witns of
      NONE => I
    | SOME w => Thm.implies_intr hyp #> compose_witness w)) (#hyps (Thm.crep_thm thm));

val satisfy_morphism = Morphism.thm_morphism o satisfy_thm;
val satisfy_facts = facts_map o morph_ctxt o satisfy_morphism;


(* rewriting with equalities *)

fun eq_morphism thy thms = Morphism.morphism
 {binding = I,
  typ = I,
  term = MetaSimplifier.rewrite_term thy thms [],
  fact = map (MetaSimplifier.rewrite_rule thms)};


(* generalize type/term parameters *)

val maxidx_atts = fold Args.maxidx_values;

fun generalize_facts inner outer facts =
  let
    val thy = ProofContext.theory_of inner;
    val maxidx =
      fold (fn ((_, atts), bs) => maxidx_atts atts #> fold (maxidx_atts o #2) bs) facts ~1;
    val exp_fact = map (Thm.adjust_maxidx_thm maxidx) #> Variable.export inner outer;
    val exp_term = Drule.term_rule thy (singleton exp_fact);
    val exp_typ = Logic.type_map exp_term;
    val morphism = Morphism.morphism {binding = I, typ = exp_typ, term = exp_term, fact = exp_fact};
  in facts_map (morph_ctxt morphism) facts end;


(* transfer to theory using closure *)

fun transfer_morphism thy =
  let val thy_ref = Theory.check_thy thy
  in Morphism.thm_morphism (fn th => transfer (Theory.deref thy_ref) th) end;



(** activate in context **)

(* init *)

fun init (Fixes fixes) = Context.map_proof (ProofContext.add_fixes fixes #> #2)
  | init (Constrains _) = I
  | init (Assumes asms) = Context.map_proof (fn ctxt =>
      let
        val asms' = Attrib.map_specs (Attrib.attribute_i (ProofContext.theory_of ctxt)) asms;
        val (_, ctxt') = ctxt
          |> fold Variable.auto_fixes (maps (map #1 o #2) asms')
          |> ProofContext.add_assms_i Assumption.assume_export asms';
      in ctxt' end)
  | init (Defines defs) = Context.map_proof (fn ctxt =>
      let
        val defs' = Attrib.map_specs (Attrib.attribute_i (ProofContext.theory_of ctxt)) defs;
        val asms = defs' |> map (fn ((name, atts), (t, ps)) =>
            let val ((c, _), t') = LocalDefs.cert_def ctxt t  (* FIXME adapt ps? *)
            in (t', ((Thm.def_binding_optional (Binding.name c) name, atts), [(t', ps)])) end);
        val (_, ctxt') = ctxt
          |> fold Variable.auto_fixes (map #1 asms)
          |> ProofContext.add_assms_i LocalDefs.def_export (map #2 asms);
      in ctxt' end)
  | init (Notes (kind, facts)) = (fn context =>
      let
        val facts' = Attrib.map_facts (Attrib.attribute_i (Context.theory_of context)) facts;
        val context' = context |> Context.mapping
          (PureThy.note_thmss kind facts' #> #2)
          (ProofContext.note_thmss kind facts' #> #2);
      in context' end);


(* activate *)

fun activate_i elem ctxt =
  let
    val elem' = map_ctxt_attrib Args.assignable elem;
    val ctxt' = Context.proof_map (init elem') ctxt;
  in (map_ctxt_attrib Args.closure elem', ctxt') end;

fun activate raw_elem ctxt =
  let val elem = raw_elem |> map_ctxt
   {binding = tap Name.of_binding,
    typ = I,
    term = I,
    pattern = I,
    fact = ProofContext.get_fact ctxt,
    attrib = Attrib.intern_src (ProofContext.theory_of ctxt)}
  in activate_i elem ctxt end;

end;