(* 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 relation_tac ctxt rel =
let
val cert = Thm.cterm_of (ProofContext.theory_of ctxt)
val rel' = cert (singleton (Variable.polymorphic ctxt) rel)
val rule = FundefCommon.get_termination_rule ctxt |> the
|> Thm.incr_indexes (#maxidx (Thm.rep_cterm rel') + 1)
val prem = #1 (Logic.dest_implies (Thm.prop_of rule))
val Rvar = cert (Var (the_single (Term.add_vars prem [])))
in rtac (Drule.cterm_instantiate [(Rvar, rel')] rule) end
fun relation_meth src =
Method.syntax Args.term src
#> (fn (ctxt, rel) => Method.SIMPLE_METHOD' (relation_tac ctxt rel))
val setup = Method.add_methods
[("relation", relation_meth,
"proves termination using a user-specified wellfounded relation")]
end