src/HOL/Codatatype/Tools/bnf_tactics.ML

tuned induction tactic

(*  Title:      HOL/Codatatype/Tools/bnf_tactics.ML
    Author:     Dmitriy Traytel, TU Muenchen
    Author:     Jasmin Blanchette, TU Muenchen
    Copyright   2012

General tactics for bounded natural functors.
*)

signature BNF_TACTICS =
sig
  val ss_only: thm list -> simpset

  val prefer_tac: int -> tactic
  val select_prem_tac: int -> (int -> tactic) -> int -> int -> tactic
  val fo_rtac: thm -> Proof.context -> int -> tactic
  val subst_asm_tac: Proof.context -> thm list -> int -> tactic
  val subst_tac: Proof.context -> thm list -> int -> tactic
  val substs_tac: Proof.context -> thm list -> int -> tactic

  val mk_flatten_assoc_tac: (int -> tactic) -> thm -> thm -> thm -> tactic
  val mk_rotate_eq_tac: (int -> tactic) -> thm -> thm -> thm -> thm -> ''a list -> ''a list ->
    int -> tactic

  val mk_Abs_bij_thm: Proof.context -> thm -> thm -> thm
  val mk_Abs_inj_thm: thm -> thm

  val mk_pred_unfold_tac: thm -> thm list -> thm -> {prems: 'a, context: Proof.context} -> tactic

  val mk_map_comp_id_tac: thm -> tactic
  val mk_map_cong_tac: int -> thm -> {prems: 'a, context: Proof.context} -> tactic
  val mk_map_congL_tac: int -> thm -> thm -> tactic
end;

structure BNF_Tactics : BNF_TACTICS =
struct

open BNF_Util

fun ss_only thms = Simplifier.clear_ss HOL_basic_ss addsimps thms;

(* FIXME: why not in "Pure"? *)
fun prefer_tac i = defer_tac i THEN PRIMITIVE (Thm.permute_prems 0 ~1);

fun select_prem_tac n tac k = DETERM o (EVERY' [REPEAT_DETERM_N (k - 1) o etac thin_rl,
  tac, REPEAT_DETERM_N (n - k) o etac thin_rl]);

(*stolen from Christian Urban's Cookbook*)
fun fo_rtac thm = Subgoal.FOCUS (fn {concl, ...} =>
  let
    val concl_pat = Drule.strip_imp_concl (cprop_of thm)
    val insts = Thm.first_order_match (concl_pat, concl)
  in
    rtac (Drule.instantiate_normalize insts thm) 1
  end);

(*unlike "unfold_tac", succeeds when the RHS contains schematic variables not in the LHS*)
fun subst_asm_tac ctxt = EqSubst.eqsubst_asm_tac ctxt [0];
fun subst_tac ctxt = EqSubst.eqsubst_tac ctxt [0];
fun substs_tac ctxt = REPEAT_DETERM oo subst_tac ctxt;



(* Theorems for open typedefs with UNIV as representing set *)

fun mk_Abs_inj_thm inj = inj OF (replicate 2 UNIV_I);
fun mk_Abs_bij_thm ctxt Abs_inj_thm surj = rule_by_tactic ctxt ((rtac surj THEN' etac exI) 1)
  (Abs_inj_thm RS @{thm bijI});



(* General tactic generators *)

(*applies assoc rule to the lhs of an equation as long as possible*)
fun mk_flatten_assoc_tac refl_tac trans assoc cong = rtac trans 1 THEN
  REPEAT_DETERM (CHANGED ((FIRST' [rtac trans THEN' rtac assoc, rtac cong THEN' refl_tac]) 1)) THEN
  refl_tac 1;

(*proves two sides of an equation to be equal assuming both are flattened and rhs can be obtained
from lhs by the given permutation of monoms*)
fun mk_rotate_eq_tac refl_tac trans assoc com cong =
  let
    fun gen_tac [] [] = K all_tac
      | gen_tac [x] [y] = if x = y then refl_tac else error "mk_rotate_eq_tac: different lists"
      | gen_tac (x :: xs) (y :: ys) = if x = y
        then rtac cong THEN' refl_tac THEN' gen_tac xs ys
        else rtac trans THEN' rtac com THEN'
          K (mk_flatten_assoc_tac refl_tac trans assoc cong) THEN'
          gen_tac (xs @ [x]) (y :: ys)
      | gen_tac _ _ = error "mk_rotate_eq_tac: different lists";
  in
    gen_tac
  end;

fun mk_pred_unfold_tac pred_def pred_defs rel_unfold {context = ctxt, prems = _} =
  Local_Defs.unfold_tac ctxt (@{thm mem_Collect_eq_split} :: pred_def :: pred_defs) THEN
  rtac rel_unfold 1;

fun mk_map_comp_id_tac map_comp =
  (rtac trans THEN' rtac map_comp) 1 THEN
  REPEAT_DETERM (stac @{thm o_id} 1) THEN
  rtac refl 1;

fun mk_map_cong_tac m map_cong {context = ctxt, prems = _} =
  EVERY' [rtac mp, rtac map_cong,
    CONJ_WRAP' (K (rtac ballI THEN' Goal.assume_rule_tac ctxt)) (1 upto m)] 1;

fun mk_map_congL_tac passive map_cong map_id' =
  (rtac trans THEN' rtac map_cong THEN' EVERY' (replicate passive (rtac refl))) 1 THEN
  REPEAT_DETERM (EVERY' [rtac trans, etac bspec, atac, rtac sym, rtac @{thm id_apply}] 1) THEN
  rtac map_id' 1;

end;