Sum.thy

    Sum		:: "(['a,'b,bool] => bool)set"
    Rep_Sum	:: "'a + 'b => (['a,'b,bool] => bool)"
    Abs_Sum	:: "(['a,'b,bool] => bool) => 'a+'b"
    Inl		:: "'a => 'a+'b"
    Inr		:: "'b => 'a+'b"
-   case		:: "['a+'b, 'a=>'c,'b=>'c] =>'c"
+   sum_case	:: "['a+'b, 'a=>'c,'b=>'c] =>'c"
 rules
   Inl_Rep_def	"Inl_Rep == (%a. %x y p. x=a & p)"
   Inr_Rep_def	"Inr_Rep == (%b. %x y p. y=b & ~p)"
   Sum_def "Sum == {f. (? a. f = Inl_Rep(a)) | (? b. f = Inr_Rep(b))}"
     (*faking a type definition...*)

   Rep_Sum_inverse 	"Abs_Sum(Rep_Sum(s)) = s"
   Abs_Sum_inverse 	"f: Sum ==> Rep_Sum(Abs_Sum(f)) = f"
     (*defining the abstract constants*)
   Inl_def  		"Inl == (%a. Abs_Sum(Inl_Rep(a)))"
   Inr_def 		"Inr == (%b. Abs_Sum(Inr_Rep(b)))"
-  case_def	"case == (%p f g. @z.  (!x. p=Inl(x) --> z=f(x))\
-\                                    & (!y. p=Inr(y) --> z=g(y)))"
+  sum_case_def	"sum_case == (%p f g. @z.  (!x. p=Inl(x) --> z=f(x))\
+\                                        & (!y. p=Inr(y) --> z=g(y)))"
 end