`Word' data type et al._(re)

Mon, 16 Jun 1997 20:17:00 -0700

Frank Heckenbach wrote:
>=20
> Peter Gerwinski wrote:
>=20
> > I noticed a lot of confusion about Integer types in GNU Pascal.
>=20
> So did I (read: I was confused in the beginning ;-). I was going to
> post something about it sometime anyway...
>=20
> >       32       Integer      Word           [unsigned] int =3D=3D long
> >       64       LongInt      LongWord       [unsigned] long long
> >
 etc etc=20

You may be interested to know the answer given by Borland to the same
problem in Delphi 2.0 when going from 16 bit to 32 bit system.=20
The following is a cut out of the Delphi help (in french however):

-------------------------------------------------------------------

Les types entiers pr=E9d=E9finis de Pascal Objet sont
divis=E9s en types fondamentaux et g=E9n=E9riques.
Les applications doivent utiliser les formats
 entiers g=E9n=E9riques chaque fois que c'est possible,
 car cela entra=EEne de meilleures performances pour
 le processeur et le syst=E8me d'exploitation.=20
Les types entiers fondamentaux devraient n'=EAtre
 utilis=E9s que lorsque l'intervalle r=E9el et/ou le
 format de stockage sont importants pour l'application.

Types fondamentaux

Les types d'entiers fondamentaux sont :

Type    Intervalle      Format

Shortint        -128 .. 127     Sign=E9, 8 bits

SmallInt        -32768 .. 32767 Sign=E9, 16 bits

Longint -2147483648 .. 2147483647       Sign=E9, 32 bits

Byte    0 .. 255        Non sign=E9, 8 bits
Word    0 .. 65535      Non sign=E9, 16 bits

L'intervalle et le format des types fondamentaux=20
sont ind=E9pendants du processeur et du syst=E8me=20
d'exploitation et ne changent pas avec les=20
diff=E9rentes impl=E9mentations de Pascal Objet.

Types g=E9n=E9riques

Les types entiers g=E9n=E9riques sont Integer et Cardinal.=20
Le type Integer type repr=E9sente un entier sign=E9 g=E9n=E9rique
 et le type Cardinal type repr=E9sente un entier non sign=E9
 g=E9n=E9rique. les intervalles r=E9els et les formats de
 stockage des types g=E9n=E9riques varient avec les=20
diff=E9rentes impl=E9mentations de Pascal Objet,=20
mais permettent g=E9n=E9ralement les op=E9rations sur=20
les entiers les plus efficaces pour le processeur=20
et le syst=E8me d'exploitation.

Type    Intervalle      Format

Integer -32768 .. 32767 Sign=E9, 16 bits

Integer -2147483648 .. 2147483647       Sign=E9, 32 bits

Cardinal        0 .. 65535      Non sign=E9, 16 bits

Cardinal        0 .. 2147483647 Non sign=E9, 32 bits

------------------------------------------------------------
=20
The idea is exactly the same as that contained in the letter of
Frank Heckenbach of today, except for the replacement of=20
Ordinal by Cardinal (which was also suggested by Franck).
So I would vote to implement what is proposed by Franck,
with only the replacement of ordinal by cardinal to have
some compatibility. i.e.
=20
Generic Types

Integer      Cardinal

Well defined types

int8      card8   (=3Dbyte is the only case without doubt)
int16     card16
int32     card32

...

          card9 =3D 0..2 POW 9 -1    ... if needed: this is always
                                   allowed by the pascal syntax
                                   but the amount of memory involved
                                   is implementation dependant:

Compatibility types
=20
anything contained in bpcompat.pas delphi1compat.pas
delphi2compat.pas and everything you need,
better than compiler switches when possible to
avoid to garble the compiler by a lot of special
purpose oddities: the idea of C to keep a minimum
in the compiler and a maximum in libraries is
not so bad (when it is possible).



--=20
                     Maurice Lombardi
Lab. Spectrometrie Physique, Universite Joseph Fourier de Grenoble, BP87
             38402 Saint Martin d'Heres Cedex FRANCE
Tel: (33) 04 7651 4751.                           Fax (33) 04 7651 4544.

Maurice Lombardi (Maurice.LOMBARDI@ujf-grenoble.fr)