(*  Title:      Pure/Isar/calculation.ML

     ID:         $Id$

     Author:     Markus Wenzel, TU Muenchen

 Generic calculational proofs.

 *)

 signature CALCULATION =

 sig

   val print_rules: Context.generic -> unit

   val get_calculation: Proof.state -> thm list option

   val trans_add: Context.generic attribute

   val trans_del: Context.generic attribute

   val sym_add: Context.generic attribute

   val sym_del: Context.generic attribute

   val symmetric: Context.generic attribute

   val also: (thmref * Attrib.src list) list option -> bool -> Proof.state -> Proof.state Seq.seq

   val also_i: thm list option -> bool -> Proof.state -> Proof.state Seq.seq

   val finally: (thmref * Attrib.src list) list option -> bool -> Proof.state -> Proof.state Seq.seq

   val finally_i: thm list option -> bool -> Proof.state -> Proof.state Seq.seq

   val moreover: bool -> Proof.state -> Proof.state

   val ultimately: bool -> Proof.state -> Proof.state

 end;

 structure Calculation: CALCULATION =

 struct

 (** calculation data **)

 structure CalculationData = GenericDataFun

 (

   val name = "Isar/calculation";

   type T = (thm NetRules.T * thm list) * (thm list * int) option;

   val empty = ((NetRules.elim, []), NONE);

   val extend = I;

   fun merge _ (((trans1, sym1), _), ((trans2, sym2), _)) =

     ((NetRules.merge (trans1, trans2), Drule.merge_rules (sym1, sym2)), NONE);

   fun print generic ((trans, sym), _) =

     let val ctxt = Context.proof_of generic in

       [Pretty.big_list "transitivity rules:"

           (map (ProofContext.pretty_thm ctxt) (NetRules.rules trans)),

         Pretty.big_list "symmetry rules:" (map (ProofContext.pretty_thm ctxt) sym)]

       |> Pretty.chunks |> Pretty.writeln

     end;

 );

 val _ = Context.add_setup [CalculationData.init];

 val print_rules = CalculationData.print;

 (* access calculation *)

 fun get_calculation state =

   (case #2 (CalculationData.get (Context.Proof (Proof.context_of state))) of

     NONE => NONE

   | SOME (thms, lev) => if lev = Proof.level state then SOME thms else NONE);

 val calculationN = "calculation";

 fun put_calculation calc =

   `Proof.level #-> (fn lev =>

     Proof.map_context (Context.the_proof o

         CalculationData.map (apsnd (K (Option.map (rpair lev) calc))) o Context.Proof))

   #> Proof.put_thms (calculationN, calc);

 (** attributes **)

 (* add/del rules *)

 val trans_add = Attrib.declaration (CalculationData.map o apfst o apfst o NetRules.insert);

 val trans_del = Attrib.declaration (CalculationData.map o apfst o apfst o NetRules.delete);

 val sym_add =

   Attrib.declaration (CalculationData.map o apfst o apsnd o Drule.add_rule)

   #> ContextRules.elim_query NONE;

 val sym_del =

   Attrib.declaration (CalculationData.map o apfst o apsnd o Drule.del_rule)

   #> ContextRules.rule_del;

 (* symmetric *)

 val symmetric = Attrib.rule (fn x => fn th =>

   (case Seq.chop (2, Drule.multi_resolves [th] (#2 (#1 (CalculationData.get x)))) of

     ([th'], _) => th'

   | ([], _) => raise THM ("symmetric: no unifiers", 1, [th])

   | _ => raise THM ("symmetric: multiple unifiers", 1, [th])));

 (* concrete syntax *)

 val trans_att = Attrib.add_del_args trans_add trans_del;

 val sym_att = Attrib.add_del_args sym_add sym_del;

 val _ = Context.add_setup

  [Attrib.add_attributes

    [("trans", Attrib.common trans_att, "declaration of transitivity rule"),

     ("sym", Attrib.common sym_att, "declaration of symmetry rule"),

     ("symmetric", Attrib.common (Attrib.no_args symmetric), "resolution with symmetry rule")],

   snd o PureThy.add_thms

    [(("", transitive_thm), [Attrib.theory trans_add]),

     (("", symmetric_thm), [Attrib.theory sym_add])]];

 (** proof commands **)

 fun err_if state b msg = if b then raise Proof.STATE (msg, state) else ();

 fun assert_sane final =

   if final then Proof.assert_forward else Proof.assert_forward_or_chain;

 fun maintain_calculation false calc = put_calculation (SOME calc)

   | maintain_calculation true calc = put_calculation NONE #> Proof.chain_facts calc;

 fun print_calculation false _ _ = ()

   | print_calculation true ctxt calc =

       Pretty.writeln (ProofContext.pretty_fact ctxt (calculationN, calc));

 (* also and finally *)

 val get_rules = #1 o CalculationData.get o Context.Proof o Proof.context_of;

 fun calculate prep_rules final raw_rules int state =

   let

     val strip_assums_concl = Logic.strip_assums_concl o Thm.prop_of;

     val eq_prop = op aconv o pairself (Pattern.eta_contract o strip_assums_concl);

     fun projection ths th = Library.exists (Library.curry eq_prop th) ths;

     val opt_rules = Option.map (prep_rules state) raw_rules;

     fun combine ths =

       (case opt_rules of SOME rules => rules

       | NONE =>

           (case ths of [] => NetRules.rules (#1 (get_rules state))

           | th :: _ => NetRules.retrieve (#1 (get_rules state)) (strip_assums_concl th)))

       |> Seq.of_list |> Seq.maps (Drule.multi_resolve ths)

       |> Seq.filter (not o projection ths);

     val facts = Proof.the_facts (assert_sane final state);

     val (initial, calculations) =

       (case get_calculation state of

         NONE => (true, Seq.single facts)

       | SOME calc => (false, Seq.map single (combine (calc @ facts))));

   in

     err_if state (initial andalso final) "No calculation yet";

     err_if state (initial andalso is_some opt_rules) "Initial calculation -- no rules to be given";

     calculations |> Seq.map (fn calc => (print_calculation int (Proof.context_of state) calc;

         state |> maintain_calculation final calc))

   end;

 val also = calculate Proof.get_thmss false;

 val also_i = calculate (K I) false;

 val finally = calculate Proof.get_thmss true;

 val finally_i = calculate (K I) true;

 (* moreover and ultimately *)

 fun collect final int state =

   let

     val facts = Proof.the_facts (assert_sane final state);

     val (initial, thms) =

       (case get_calculation state of

         NONE => (true, [])

       | SOME thms => (false, thms));

     val calc = thms @ facts;

   in

     err_if state (initial andalso final) "No calculation yet";

     print_calculation int (Proof.context_of state) calc;

     state |> maintain_calculation final calc

   end;

 val moreover = collect false;

 val ultimately = collect true;

 end;