(* Title: HOL/Tools/Function/relation.ML
Author: Alexander Krauss, TU Muenchen
Tactics to start a termination proof using a user-specified relation.
*)
signature FUNCTION_RELATION =
sig
val relation_tac: Proof.context -> (typ -> term) -> int -> tactic
val relation_infer_tac: Proof.context -> term -> int -> tactic
end
structure Function_Relation: FUNCTION_RELATION =
struct
(* tactic version *)
fun inst_state_tac ctxt inst =
SUBGOAL (fn (goal, _) =>
(case Term.add_vars goal [] of
[v as (_, T)] => PRIMITIVE (Thm.instantiate ([], [(v, Thm.cterm_of ctxt (inst T))]))
| _ => no_tac));
fun relation_tac ctxt rel i =
TRY (Function_Common.termination_rule_tac ctxt i)
THEN inst_state_tac ctxt rel i;
(* version with type inference *)
fun inst_state_infer_tac ctxt rel =
SUBGOAL (fn (goal, _) =>
(case Term.add_vars goal [] of
[v as (_, T)] =>
let
val rel' =
singleton (Variable.polymorphic ctxt) rel
|> map_types Type_Infer.paramify_vars
|> Type.constraint T
|> Syntax.check_term ctxt;
in PRIMITIVE (Thm.instantiate ([], [(v, Thm.cterm_of ctxt rel')])) end
| _ => no_tac));
fun relation_infer_tac ctxt rel i =
TRY (Function_Common.termination_rule_tac ctxt i)
THEN inst_state_infer_tac ctxt rel i;
end