TFL/dcterm.ML

+(*  Title:      TFL/dcterm.ML
+    ID:         $Id$
+    Author:     Konrad Slind, Cambridge University Computer Laboratory
+    Copyright   1997  University of Cambridge
+*)
+
+(*---------------------------------------------------------------------------
+ * Derived efficient cterm destructors.
+ *---------------------------------------------------------------------------*)
+
+signature DCTERM =
+sig
+  val dest_comb: cterm -> cterm * cterm
+  val dest_abs: string option -> cterm -> cterm * cterm
+  val capply: cterm -> cterm -> cterm
+  val cabs: cterm -> cterm -> cterm
+  val mk_conj: cterm * cterm -> cterm
+  val mk_disj: cterm * cterm -> cterm
+  val mk_exists: cterm * cterm -> cterm
+  val dest_conj: cterm -> cterm * cterm
+  val dest_const: cterm -> {Name: string, Ty: typ}
+  val dest_disj: cterm -> cterm * cterm
+  val dest_eq: cterm -> cterm * cterm
+  val dest_exists: cterm -> cterm * cterm
+  val dest_forall: cterm -> cterm * cterm
+  val dest_imp: cterm -> cterm * cterm
+  val dest_let: cterm -> cterm * cterm
+  val dest_neg: cterm -> cterm
+  val dest_pair: cterm -> cterm * cterm
+  val dest_var: cterm -> {Name:string, Ty:typ}
+  val is_conj: cterm -> bool
+  val is_cons: cterm -> bool
+  val is_disj: cterm -> bool
+  val is_eq: cterm -> bool
+  val is_exists: cterm -> bool
+  val is_forall: cterm -> bool
+  val is_imp: cterm -> bool
+  val is_let: cterm -> bool
+  val is_neg: cterm -> bool
+  val is_pair: cterm -> bool
+  val list_mk_disj: cterm list -> cterm
+  val strip_abs: cterm -> cterm list * cterm
+  val strip_comb: cterm -> cterm * cterm list
+  val strip_disj: cterm -> cterm list
+  val strip_exists: cterm -> cterm list * cterm
+  val strip_forall: cterm -> cterm list * cterm
+  val strip_imp: cterm -> cterm list * cterm
+  val drop_prop: cterm -> cterm
+  val mk_prop: cterm -> cterm
+end;
+
+structure Dcterm: DCTERM =
+struct
+
+structure U = Utils;
+
+fun ERR func mesg = U.ERR {module = "Dcterm", func = func, mesg = mesg};
+
+
+fun dest_comb t = Thm.dest_comb t
+  handle CTERM msg => raise ERR "dest_comb" msg;
+
+fun dest_abs a t = Thm.dest_abs a t
+  handle CTERM msg => raise ERR "dest_abs" msg;
+
+fun capply t u = Thm.capply t u
+  handle CTERM msg => raise ERR "capply" msg;
+
+fun cabs a t = Thm.cabs a t
+  handle CTERM msg => raise ERR "cabs" msg;
+
+
+(*---------------------------------------------------------------------------
+ * Some simple constructor functions.
+ *---------------------------------------------------------------------------*)
+
+val mk_hol_const = Thm.cterm_of (Theory.sign_of HOL.thy) o Const;
+
+fun mk_exists (r as (Bvar, Body)) =
+  let val ty = #T(rep_cterm Bvar)
+      val c = mk_hol_const("Ex", (ty --> HOLogic.boolT) --> HOLogic.boolT)
+  in capply c (uncurry cabs r) end;
+
+
+local val c = mk_hol_const("op &", HOLogic.boolT --> HOLogic.boolT --> HOLogic.boolT)
+in fun mk_conj(conj1,conj2) = capply (capply c conj1) conj2
+end;
+
+local val c = mk_hol_const("op |", HOLogic.boolT --> HOLogic.boolT --> HOLogic.boolT)
+in fun mk_disj(disj1,disj2) = capply (capply c disj1) disj2
+end;
+
+
+(*---------------------------------------------------------------------------
+ * The primitives.
+ *---------------------------------------------------------------------------*)
+fun dest_const ctm =
+   (case #t(rep_cterm ctm)
+      of Const(s,ty) => {Name = s, Ty = ty}
+       | _ => raise ERR "dest_const" "not a constant");
+
+fun dest_var ctm =
+   (case #t(rep_cterm ctm)
+      of Var((s,i),ty) => {Name=s, Ty=ty}
+       | Free(s,ty)    => {Name=s, Ty=ty}
+       |             _ => raise ERR "dest_var" "not a variable");
+
+
+(*---------------------------------------------------------------------------
+ * Derived destructor operations.
+ *---------------------------------------------------------------------------*)
+
+fun dest_monop expected tm =
+ let
+   fun err () = raise ERR "dest_monop" ("Not a(n) " ^ quote expected);
+   val (c, N) = dest_comb tm handle U.ERR _ => err ();
+   val name = #Name (dest_const c handle U.ERR _ => err ());
+ in if name = expected then N else err () end;
+
+fun dest_binop expected tm =
+ let
+   fun err () = raise ERR "dest_binop" ("Not a(n) " ^ quote expected);
+   val (M, N) = dest_comb tm handle U.ERR _ => err ()
+ in (dest_monop expected M, N) handle U.ERR _ => err () end;
+
+fun dest_binder expected tm =
+  dest_abs None (dest_monop expected tm)
+  handle U.ERR _ => raise ERR "dest_binder" ("Not a(n) " ^ quote expected);
+
+
+val dest_neg    = dest_monop "not"
+val dest_pair   = dest_binop "Pair";
+val dest_eq     = dest_binop "op ="
+val dest_imp    = dest_binop "op -->"
+val dest_conj   = dest_binop "op &"
+val dest_disj   = dest_binop "op |"
+val dest_cons   = dest_binop "Cons"
+val dest_let    = Library.swap o dest_binop "Let";
+val dest_select = dest_binder "Eps"
+val dest_exists = dest_binder "Ex"
+val dest_forall = dest_binder "All"
+
+(* Query routines *)
+
+val is_eq     = can dest_eq
+val is_imp    = can dest_imp
+val is_select = can dest_select
+val is_forall = can dest_forall
+val is_exists = can dest_exists
+val is_neg    = can dest_neg
+val is_conj   = can dest_conj
+val is_disj   = can dest_disj
+val is_pair   = can dest_pair
+val is_let    = can dest_let
+val is_cons   = can dest_cons
+
+
+(*---------------------------------------------------------------------------
+ * Iterated creation.
+ *---------------------------------------------------------------------------*)
+val list_mk_disj = U.end_itlist (fn d1 => fn tm => mk_disj (d1, tm));
+
+(*---------------------------------------------------------------------------
+ * Iterated destruction. (To the "right" in a term.)
+ *---------------------------------------------------------------------------*)
+fun strip break tm =
+  let fun dest (p as (ctm,accum)) =
+        let val (M,N) = break ctm
+        in dest (N, M::accum)
+        end handle U.ERR _ => p
+  in dest (tm,[])
+  end;
+
+fun rev2swap (x,l) = (rev l, x);
+
+val strip_comb   = strip (Library.swap o dest_comb)  (* Goes to the "left" *)
+val strip_imp    = rev2swap o strip dest_imp
+val strip_abs    = rev2swap o strip (dest_abs None)
+val strip_forall = rev2swap o strip dest_forall
+val strip_exists = rev2swap o strip dest_exists
+
+val strip_disj   = rev o (op::) o strip dest_disj
+
+
+(*---------------------------------------------------------------------------
+ * Going into and out of prop
+ *---------------------------------------------------------------------------*)
+
+fun mk_prop ctm =
+  let val {t, sign, ...} = Thm.rep_cterm ctm in
+    if can HOLogic.dest_Trueprop t then ctm
+    else Thm.cterm_of sign (HOLogic.mk_Trueprop t)
+  end
+  handle TYPE (msg, _, _) => raise ERR "mk_prop" msg
+    | TERM (msg, _) => raise ERR "mk_prop" msg;
+
+fun drop_prop ctm = dest_monop "Trueprop" ctm handle U.ERR _ => ctm;
+
+
+end;