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