src/HOL/Tools/function_package/auto_term.ML
author wenzelm
Wed, 31 Dec 2008 18:53:16 +0100
changeset 29270 0eade173f77e
parent 25545 21cd20c1ce98
child 30510 4120fc59dd85
permissions -rw-r--r--
moved old add_type_XXX, add_term_XXX etc. to structure OldTerm;

(*  Title:      HOL/Tools/function_package/auto_term.ML
    ID:         $Id$
    Author:     Alexander Krauss, TU Muenchen

A package for general recursive function definitions.
Method "relation" to commence a termination proof using a user-specified relation.
*)

signature FUNDEF_RELATION =
sig
  val relation_tac: Proof.context -> term -> int -> tactic
  val setup: theory -> theory
end

structure FundefRelation : FUNDEF_RELATION =
struct

fun inst_thm ctxt rel st =
    let
      val cert = Thm.cterm_of (ProofContext.theory_of ctxt)
      val rel' = cert (singleton (Variable.polymorphic ctxt) rel)
      val st' = Thm.incr_indexes (#maxidx (Thm.rep_cterm rel') + 1) st
      val Rvar = cert (Var (the_single (Term.add_vars (prop_of st') [])))
    in 
      Drule.cterm_instantiate [(Rvar, rel')] st' 
    end

fun relation_tac ctxt rel i = 
    TRY (FundefCommon.apply_termination_rule ctxt i)
    THEN PRIMITIVE (inst_thm ctxt rel)

val setup = Method.add_methods
  [("relation", (Method.SIMPLE_METHOD' o (fn (rel, ctxt) => relation_tac ctxt rel)) oo (Method.syntax Args.term),
    "proves termination using a user-specified wellfounded relation")]

end