author nipkow Fri Nov 28 07:35:10 1997 +0100 (1997-11-28) changeset 4318 9b672ea2dfe7 parent 4317 7264fa2ff2ec child 4319 afb60b8bf15e
Fixed the definition of `termord': is now antisymmetric.
 src/Pure/logic.ML file | annotate | diff | revisions
```     1.1 --- a/src/Pure/logic.ML	Thu Nov 27 19:39:02 1997 +0100
1.2 +++ b/src/Pure/logic.ML	Fri Nov 28 07:35:10 1997 +0100
1.3 @@ -314,16 +314,34 @@
1.4
1.5  (*** term order ***)
1.6
1.7 -(* NB: non-linearity of the ordering is not a soundness problem *)
1.8 +fun dest_hd(Const(a,T)) = (a,T,0)
1.9 +  | dest_hd(Free(a,T))  = (a,T,1)
1.10 +  | dest_hd(Var(v,T))   = (Syntax.string_of_vname v, T, 2)
1.11 +  | dest_hd(Bound i)    = (string_of_int i,dummyT,3)
1.12 +  | dest_hd(Abs(x,T,_)) = (x,T,4);
1.13
1.14 -(* FIXME: "***ABSTRACTION***" is a hack and makes the ordering non-linear *)
1.15 -fun string_of_hd(Const(a,_)) = a
1.16 -  | string_of_hd(Free(a,_))  = a
1.17 -  | string_of_hd(Var(v,_))   = Syntax.string_of_vname v
1.18 -  | string_of_hd(Bound i)    = string_of_int i
1.19 -  | string_of_hd(Abs _)      = "***ABSTRACTION***";
1.20 +(* assumes that vars/frees with the same name have same classes *)
1.21 +fun typord(T,U) = if T=U then EQUAL else
1.22 + (case (T,U) of
1.23 +    (Type(a,Ts),Type(b,Us)) =>
1.24 +      (case stringord(a,b) of EQUAL => lextypord(Ts,Us) | ord => ord)
1.25 +  | (Type _, _) => GREATER
1.26 +  | (TFree _,Type _) => LESS
1.27 +  | (TFree(a,_),TFree(b,_)) => stringord(a,b)
1.28 +  | (TFree _, TVar _) => GREATER
1.29 +  | (TVar _,Type _) => LESS
1.30 +  | (TVar _,TFree _) => LESS
1.31 +  | (TVar(va,_),TVar(vb,_)) =>
1.32 +      stringord(Syntax.string_of_vname va,Syntax.string_of_vname vb))
1.33 +and lextypord(T::Ts,U::Us) =
1.34 +      (case typord(T,U) of
1.35 +         EQUAL => lextypord(Ts,Us)
1.36 +       | ord   => ord)
1.37 +  | lextypord([],[]) = EQUAL
1.38 +  | lextypord _ = error("lextypord");
1.39
1.40 -(* a strict (not reflexive) linear well-founded AC-compatible ordering
1.41 +
1.42 +(* a linear well-founded AC-compatible ordering
1.43   * for terms:
1.44   * s < t <=> 1. size(s) < size(t) or
1.45               2. size(s) = size(t) and s=f(...) and t = g(...) and f<g or
1.46 @@ -331,14 +349,18 @@
1.47                  (s1..sn) < (t1..tn) (lexicographically)
1.48   *)
1.49
1.50 -(* FIXME: should really take types into account as well.
1.51 - * Otherwise non-linear *)
1.52 -fun termord(Abs(_,_,t),Abs(_,_,u)) = termord(t,u)
1.53 +fun termord(Abs(x,T,t),Abs(y,U,u)) =
1.54 +      (case termord(t,u) of EQUAL => typord(T,U) | ord => ord)
1.55    | termord(t,u) =
1.56        (case intord(size_of_term t,size_of_term u) of
1.57           EQUAL => let val (f,ts) = strip_comb t and (g,us) = strip_comb u
1.58 -                  in case stringord(string_of_hd f, string_of_hd g) of
1.59 -                       EQUAL => lextermord(ts,us)
1.60 +                      val (a,T,i) = dest_hd f and (b,U,j) = dest_hd g
1.61 +                  in case stringord(a,b) of
1.62 +                       EQUAL => (case typord(T,U) of
1.63 +                                   EQUAL => (case intord(i,j) of
1.64 +                                               EQUAL => lextermord(ts,us)
1.65 +                                             | ord => ord)
1.66 +                                 | ord => ord)
1.67                       | ord   => ord
1.68                    end
1.69         | ord => ord)
```