Enumerated types_(re)

Mon, 09 Jun 1997 20:07:07 +0200

Phil Nelson wrote:
> =

> >type TComparisonResult=3D(Less value -1, Equals, Greater, Strange valu=
e 10);
> >
> >i.e. Ord(Less)=3D-1, Ord(Equals)=3D0, Ord(Greater)=3D1, Ord(Strange)=3D=
10.
> =

> Another problem ... it will make pred() and succ() harder if they must
> do succ(Greater) =3D> Strange and pred(Strange) =3D> Greater.  I think =

> setting the initial value would be reasonable, but not allowing a
> jump in the values.


Only allowing to set the initial offset would make this kind of fetaure
useless. Implementing succ and pred functions using a simple table will
not cause much trouble.
 =

Imagine this (for me very actual) problem:

Type assembler_instructions =3D ( add_x, sub_y, mul_a_x) ; =

                             (* course more complex*)
     register_type          =3D ( ax, bx, dx, bc, de, hl );

     objectfile =3D record =

                    ai     : assembler_instruction;
                    p1, p2 : register_type;
                  end;

(* using some ada-style for making the example *)
    =

for assembler_instructions use =

 ( add_x =3D> 27, =

   sub_y =3D> 37,
   mul_a_x =3D> 127);

for register_type use
 ( ax =3D> 12,
   bx =3D> 22, =

   dx =3D> 32,
   bc =3D> 01,
   de =3D> 17,
   hl =3D> 33);


The ord-function will, assuming you order the register-names in a simple
index only cause code to extract the real ord number from a table, i.e. =


ord_values : array (.enumeration_type.) of integer; =

(* the array keeping the values*)


Just suggesting :)


/Jakob :)

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Jakob Heinemann (Jakob.Heinemann@ericsson.com)