src/Tools/induction.ML
author wenzelm
Thu Apr 10 10:36:29 2014 +0200 (2014-04-10)
changeset 56506 c1f04411d43f
parent 45014 0e847655b2d8
child 58826 2ed2eaabe3df
permissions -rw-r--r--
tuned;
     1 signature INDUCTION =
     2 sig
     3   val induction_tac: Proof.context -> bool -> (binding option * (term * bool)) option list list ->
     4     (string * typ) list list -> term option list -> thm list option ->
     5     thm list -> int -> cases_tactic
     6   val setup: theory -> theory
     7 end
     8 
     9 structure Induction: INDUCTION =
    10 struct
    11 
    12 val ind_hypsN = "IH";
    13 
    14 fun preds_of t =
    15  (case strip_comb t of
    16     (p as Var _, _) => [p]
    17   | (p as Free _, _) => [p]
    18   | (_, ts) => flat(map preds_of ts))
    19 
    20 fun name_hyps (arg as ((cases, consumes), th)) =
    21   if not(forall (null o #2 o #1) cases) then arg
    22   else
    23     let
    24       val (prems, concl) = Logic.strip_horn (prop_of th);
    25       val prems' = drop consumes prems;
    26       val ps = preds_of concl;
    27 
    28       fun hname_of t =
    29         if exists_subterm (member (op =) ps) t
    30         then ind_hypsN else Rule_Cases.case_hypsN
    31 
    32       val hnamess = map (map hname_of o Logic.strip_assums_hyp) prems'
    33       val n = Int.min (length hnamess, length cases) 
    34       val cases' = map (fn (((cn,_),concls),hns) => ((cn,hns),concls))
    35         (take n cases ~~ take n hnamess)
    36     in ((cases',consumes),th) end
    37 
    38 val induction_tac = Induct.gen_induct_tac (K name_hyps)
    39 
    40 val setup = Induct.gen_induct_setup @{binding induction} induction_tac
    41 
    42 end
    43