src/Pure/logic.ML
author wenzelm
Tue May 31 11:53:21 2005 +0200 (2005-05-31)
changeset 16130 38b111451155
parent 15596 8665d08085df
child 16846 bbebc68a7faf
permissions -rw-r--r--
added nth_prem;
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(*  Title:      Pure/logic.ML
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    ID:         $Id$
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    Author:     Lawrence C Paulson, Cambridge University Computer Laboratory
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    Copyright   Cambridge University 1992
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Abstract syntax operations of the Pure meta-logic.
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*)
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infix occs;
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signature LOGIC =
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sig
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  val is_all            : term -> bool
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  val mk_equals         : term * term -> term
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  val dest_equals       : term -> term * term
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  val is_equals         : term -> bool
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  val mk_implies        : term * term -> term
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  val dest_implies      : term -> term * term
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  val is_implies        : term -> bool
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  val list_implies      : term list * term -> term
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  val strip_imp_prems   : term -> term list
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  val strip_imp_concl   : term -> term
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  val strip_prems       : int * term list * term -> term list * term
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  val count_prems       : term * int -> int
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  val nth_prem		: int * term -> term
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  val mk_conjunction    : term * term -> term
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  val mk_conjunction_list: term list -> term
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  val strip_horn        : term -> term list * term
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  val mk_cond_defpair   : term list -> term * term -> string * term
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  val mk_defpair        : term * term -> string * term
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  val mk_type           : typ -> term
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  val dest_type         : term -> typ
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  val mk_inclass        : typ * class -> term
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  val dest_inclass      : term -> typ * class
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  val goal_const        : term
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  val mk_goal           : term -> term
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  val dest_goal         : term -> term
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  val occs              : term * term -> bool
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  val close_form        : term -> term
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  val incr_indexes      : typ list * int -> term -> term
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  val lift_fns          : term * int -> (term -> term) * (term -> term)
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  val strip_assums_hyp  : term -> term list
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  val strip_assums_concl: term -> term
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  val strip_params      : term -> (string * typ) list
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  val has_meta_prems    : term -> int -> bool
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  val flatten_params    : int -> term -> term
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  val auto_rename       : bool ref
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  val set_rename_prefix : string -> unit
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  val list_rename_params: string list * term -> term
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  val assum_pairs       : int * term -> (term*term)list
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  val varify            : term -> term
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  val unvarify          : term -> term
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  val get_goal          : term -> int -> term
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  val goal_params       : term -> int -> term * term list
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  val prems_of_goal     : term -> int -> term list
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  val concl_of_goal     : term -> int -> term
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end;
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structure Logic : LOGIC =
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struct
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(*** Abstract syntax operations on the meta-connectives ***)
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(** all **)
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fun is_all (Const ("all", _) $ _) = true
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  | is_all _ = false;
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(** equality **)
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(*Make an equality.  DOES NOT CHECK TYPE OF u*)
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fun mk_equals(t,u) = equals(fastype_of t) $ t $ u;
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fun dest_equals (Const("==",_) $ t $ u)  =  (t,u)
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  | dest_equals t = raise TERM("dest_equals", [t]);
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fun is_equals (Const ("==", _) $ _ $ _) = true
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  | is_equals _ = false;
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(** implies **)
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fun mk_implies(A,B) = implies $ A $ B;
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fun dest_implies (Const("==>",_) $ A $ B)  =  (A,B)
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  | dest_implies A = raise TERM("dest_implies", [A]);
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fun is_implies (Const ("==>", _) $ _ $ _) = true
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  | is_implies _ = false;
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(** nested implications **)
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(* [A1,...,An], B  goes to  A1==>...An==>B  *)
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fun list_implies ([], B) = B : term
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  | list_implies (A::AS, B) = implies $ A $ list_implies(AS,B);
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(* A1==>...An==>B  goes to  [A1,...,An], where B is not an implication *)
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fun strip_imp_prems (Const("==>", _) $ A $ B) = A :: strip_imp_prems B
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  | strip_imp_prems _ = [];
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(* A1==>...An==>B  goes to B, where B is not an implication *)
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fun strip_imp_concl (Const("==>", _) $ A $ B) = strip_imp_concl B
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  | strip_imp_concl A = A : term;
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(*Strip and return premises: (i, [], A1==>...Ai==>B)
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    goes to   ([Ai, A(i-1),...,A1] , B)         (REVERSED)
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  if  i<0 or else i too big then raises  TERM*)
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fun strip_prems (0, As, B) = (As, B)
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  | strip_prems (i, As, Const("==>", _) $ A $ B) =
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        strip_prems (i-1, A::As, B)
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  | strip_prems (_, As, A) = raise TERM("strip_prems", A::As);
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(*Count premises -- quicker than (length o strip_prems) *)
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fun count_prems (Const("==>", _) $ A $ B, n) = count_prems (B,n+1)
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  | count_prems (_,n) = n;
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(*Select Ai from A1 ==>...Ai==>B*)
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fun nth_prem (1, Const ("==>", _) $ A $ _) = A
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  | nth_prem (i, Const ("==>", _) $ _ $ B) = nth_prem (i - 1, B)
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  | nth_prem (_, A) = raise TERM ("nth_prem", [A]);
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(*strip a proof state (Horn clause):
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  B1 ==> ... Bn ==> C   goes to   ([B1, ..., Bn], C)    *)
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fun strip_horn A = (strip_imp_prems A, strip_imp_concl A);
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(** conjunction **)
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fun mk_conjunction (t, u) =
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  Term.list_all ([("C", propT)], mk_implies (list_implies ([t, u], Bound 0), Bound 0));
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fun mk_conjunction_list [] = Term.all propT $ Abs ("dummy", propT, mk_implies (Bound 0, Bound 0))
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  | mk_conjunction_list ts = foldr1 mk_conjunction ts;
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(** definitions **)
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fun mk_cond_defpair As (lhs, rhs) =
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  (case Term.head_of lhs of
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    Const (name, _) =>
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      (Sign.base_name name ^ "_def", list_implies (As, mk_equals (lhs, rhs)))
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  | _ => raise TERM ("Malformed definition: head of lhs not a constant", [lhs, rhs]));
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fun mk_defpair lhs_rhs = mk_cond_defpair [] lhs_rhs;
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(** types as terms **)
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fun mk_type ty = Const ("TYPE", itselfT ty);
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fun dest_type (Const ("TYPE", Type ("itself", [ty]))) = ty
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  | dest_type t = raise TERM ("dest_type", [t]);
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(** class constraints **)
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fun mk_inclass (ty, c) =
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  Const (Sign.const_of_class c, itselfT ty --> propT) $ mk_type ty;
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fun dest_inclass (t as Const (c_class, _) $ ty) =
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      ((dest_type ty, Sign.class_of_const c_class)
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        handle TERM _ => raise TERM ("dest_inclass", [t]))
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  | dest_inclass t = raise TERM ("dest_inclass", [t]);
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(** atomic goals **)
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val goal_const = Const ("Goal", propT --> propT);
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fun mk_goal t = goal_const $ t;
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fun dest_goal (Const ("Goal", _) $ t) = t
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  | dest_goal t = raise TERM ("dest_goal", [t]);
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(*** Low-level term operations ***)
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(*Does t occur in u?  Or is alpha-convertible to u?
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  The term t must contain no loose bound variables*)
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fun t occs u = exists_subterm (fn s => t aconv s) u;
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(*Close up a formula over all free variables by quantification*)
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fun close_form A =
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  list_all_free (sort_wrt fst (map dest_Free (term_frees A)), A);
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(*** Specialized operations for resolution... ***)
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(*For all variables in the term, increment indexnames and lift over the Us
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    result is ?Gidx(B.(lev+n-1),...,B.lev) where lev is abstraction level *)
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fun incr_indexes (Us: typ list, inc:int) t =
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  let fun incr (Var ((a,i), T), lev) =
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                Unify.combound (Var((a, i+inc), Us---> incr_tvar inc T),
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                                lev, length Us)
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        | incr (Abs (a,T,body), lev) =
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                Abs (a, incr_tvar inc T, incr(body,lev+1))
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        | incr (Const(a,T),_) = Const(a, incr_tvar inc T)
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        | incr (Free(a,T),_) = Free(a, incr_tvar inc T)
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        | incr (f$t, lev) = incr(f,lev) $ incr(t,lev)
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        | incr (t,lev) = t
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  in  incr(t,0)  end;
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(*Make lifting functions from subgoal and increment.
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    lift_abs operates on tpairs (unification constraints)
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    lift_all operates on propositions     *)
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fun lift_fns (B,inc) =
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  let fun lift_abs (Us, Const("==>", _) $ _ $ B) u = lift_abs (Us,B) u
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        | lift_abs (Us, Const("all",_)$Abs(a,T,t)) u =
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              Abs(a, T, lift_abs (T::Us, t) u)
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        | lift_abs (Us, _) u = incr_indexes(rev Us, inc) u
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      fun lift_all (Us, Const("==>", _) $ A $ B) u =
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              implies $ A $ lift_all (Us,B) u
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        | lift_all (Us, Const("all",_)$Abs(a,T,t)) u =
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              all T $ Abs(a, T, lift_all (T::Us,t) u)
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        | lift_all (Us, _) u = incr_indexes(rev Us, inc) u;
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  in  (lift_abs([],B), lift_all([],B))  end;
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(*Strips assumptions in goal, yielding list of hypotheses.   *)
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fun strip_assums_hyp (Const("==>", _) $ H $ B) = H :: strip_assums_hyp B
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  | strip_assums_hyp (Const("all",_)$Abs(a,T,t)) = strip_assums_hyp t
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  | strip_assums_hyp B = [];
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(*Strips assumptions in goal, yielding conclusion.   *)
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fun strip_assums_concl (Const("==>", _) $ H $ B) = strip_assums_concl B
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  | strip_assums_concl (Const("all",_)$Abs(a,T,t)) = strip_assums_concl t
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  | strip_assums_concl B = B;
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(*Make a list of all the parameters in a subgoal, even if nested*)
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fun strip_params (Const("==>", _) $ H $ B) = strip_params B
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  | strip_params (Const("all",_)$Abs(a,T,t)) = (a,T) :: strip_params t
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  | strip_params B = [];
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(*test for meta connectives in prems of a 'subgoal'*)
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fun has_meta_prems prop i =
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  let
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    fun is_meta (Const ("==>", _) $ _ $ _) = true
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      | is_meta (Const ("==", _) $ _ $ _) = true
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      | is_meta (Const ("all", _) $ _) = true
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      | is_meta _ = false;
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  in
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    (case strip_prems (i, [], prop) of
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      (B :: _, _) => exists is_meta (strip_assums_hyp B)
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    | _ => false) handle TERM _ => false
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  end;
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(*Removes the parameters from a subgoal and renumber bvars in hypotheses,
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    where j is the total number of parameters (precomputed)
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  If n>0 then deletes assumption n. *)
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fun remove_params j n A =
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    if j=0 andalso n<=0 then A  (*nothing left to do...*)
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    else case A of
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        Const("==>", _) $ H $ B =>
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          if n=1 then                           (remove_params j (n-1) B)
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          else implies $ (incr_boundvars j H) $ (remove_params j (n-1) B)
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      | Const("all",_)$Abs(a,T,t) => remove_params (j-1) n t
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      | _ => if n>0 then raise TERM("remove_params", [A])
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             else A;
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(** Auto-renaming of parameters in subgoals **)
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val auto_rename = ref false
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and rename_prefix = ref "ka";
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(*rename_prefix is not exported; it is set by this function.*)
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fun set_rename_prefix a =
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    if a<>"" andalso forall Symbol.is_letter (Symbol.explode a)
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    then  (rename_prefix := a;  auto_rename := true)
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    else  error"rename prefix must be nonempty and consist of letters";
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(*Makes parameters in a goal have distinctive names (not guaranteed unique!)
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  A name clash could cause the printer to rename bound vars;
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    then res_inst_tac would not work properly.*)
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fun rename_vars (a, []) = []
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  | rename_vars (a, (_,T)::vars) =
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        (a,T) :: rename_vars (Symbol.bump_string a, vars);
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(*Move all parameters to the front of the subgoal, renaming them apart;
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  if n>0 then deletes assumption n. *)
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fun flatten_params n A =
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    let val params = strip_params A;
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        val vars = if !auto_rename
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                   then rename_vars (!rename_prefix, params)
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                   else ListPair.zip (variantlist(map #1 params,[]),
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                                      map #2 params)
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    in  list_all (vars, remove_params (length vars) n A)
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    end;
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(*Makes parameters in a goal have the names supplied by the list cs.*)
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fun list_rename_params (cs, Const("==>", _) $ A $ B) =
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      implies $ A $ list_rename_params (cs, B)
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  | list_rename_params (c::cs, Const("all",_)$Abs(_,T,t)) =
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      all T $ Abs(c, T, list_rename_params (cs, t))
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  | list_rename_params (cs, B) = B;
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(*** Treatmsent of "assume", "erule", etc. ***)
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(*Strips assumptions in goal yielding  
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   HS = [Hn,...,H1],   params = [xm,...,x1], and B,
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  where x1...xm are the parameters. This version (21.1.2005) REQUIRES 
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  the the parameters to be flattened, but it allows erule to work on 
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  assumptions of the form !!x. phi. Any !! after the outermost string
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  will be regarded as belonging to the conclusion, and left untouched.
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  Used ONLY by assum_pairs.
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      Unless nasms<0, it can terminate the recursion early; that allows
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  erule to work on assumptions of the form P==>Q.*)
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fun strip_assums_imp (0, Hs, B) = (Hs, B)  (*recursion terminated by nasms*)
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  | strip_assums_imp (nasms, Hs, Const("==>", _) $ H $ B) = 
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      strip_assums_imp (nasms-1, H::Hs, B)
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  | strip_assums_imp (_, Hs, B) = (Hs, B); (*recursion terminated by B*)
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(*Strips OUTER parameters only, unlike similar legacy versions.*)
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fun strip_assums_all (params, Const("all",_)$Abs(a,T,t)) =
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      strip_assums_all ((a,T)::params, t)
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  | strip_assums_all (params, B) = (params, B);
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(*Produces disagreement pairs, one for each assumption proof, in order.
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  A is the first premise of the lifted rule, and thus has the form
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    H1 ==> ... Hk ==> B   and the pairs are (H1,B),...,(Hk,B).
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  nasms is the number of assumptions in the original subgoal, needed when B
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    has the form B1 ==> B2: it stops B1 from being taken as an assumption. *)
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fun assum_pairs(nasms,A) =
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  let val (params, A') = strip_assums_all ([],A)
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      val (Hs,B) = strip_assums_imp (nasms,[],A')
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      fun abspar t = Unify.rlist_abs(params, t)
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      val D = abspar B
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      fun pairrev ([], pairs) = pairs
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        | pairrev (H::Hs, pairs) = pairrev(Hs,  (abspar H, D) :: pairs)
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  in  pairrev (Hs,[])
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  end;
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(*Converts Frees to Vars and TFrees to TVars so that axioms can be written
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  without (?) everywhere*)
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fun varify (Const(a,T)) = Const(a, Type.varifyT T)
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  | varify (Free(a,T)) = Var((a,0), Type.varifyT T)
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  | varify (Var(ixn,T)) = Var(ixn, Type.varifyT T)
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  | varify (Abs (a,T,body)) = Abs (a, Type.varifyT T, varify body)
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  | varify (f$t) = varify f $ varify t
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  | varify t = t;
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(*Inverse of varify.  Converts axioms back to their original form.*)
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fun unvarify (Const(a,T))    = Const(a, Type.unvarifyT T)
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  | unvarify (Free(a,T))     = Free(a, Type.unvarifyT T)  (* CB: added *)
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  | unvarify (Var((a,0), T)) = Free(a, Type.unvarifyT T)
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  | unvarify (Var(ixn,T))    = Var(ixn, Type.unvarifyT T)  (*non-0 index!*)
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  | unvarify (Abs (a,T,body)) = Abs (a, Type.unvarifyT T, unvarify body)
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  | unvarify (f$t) = unvarify f $ unvarify t
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  | unvarify t = t;
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(*Get subgoal i*)
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fun get_goal st i = List.nth (strip_imp_prems st, i-1)
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  handle Subscript => error "Goal number out of range";
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(*reverses parameters for substitution*)
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fun goal_params st i =
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  let val gi = get_goal st i
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      val rfrees = map Free (rename_wrt_term gi (strip_params gi))
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  in (gi, rfrees) end;
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fun concl_of_goal st i =
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  let val (gi, rfrees) = goal_params st i
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      val B = strip_assums_concl gi
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  in subst_bounds (rfrees, B) end;
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fun prems_of_goal st i =
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  let val (gi, rfrees) = goal_params st i
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      val As = strip_assums_hyp gi
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  in map (fn A => subst_bounds (rfrees, A)) As end;
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end;