From help-request at octave dot org Sun Sep  5 14:42:36 2004
Subject: Re: int8(0) == int16(0) [ was Re: int8(0)==0 ? ]
From: "John W. Eaton" <jwe at bevo dot che dot wisc dot edu>
To: David Bateman <David dot Bateman at motorola dot com>
Cc: Josep =?iso-8859-1?Q?Mon=E9s?= i Teixidor <jmones at puntbarra dot com>,         "Llista help a octave.org" <help@octave.org>
Date: Sun, 5 Sep 2004 15:38:30 -0400

On  5-Sep-2004, David Bateman <David dot Bateman at motorola dot com> wrote:

| According to John W. Eaton <jwe at bevo dot che dot wisc dot edu> (on 09/04/04):
| > On  3-Sep-2004, Josep Mon=E9s i Teixidor <jmones at puntbarra dot com> wro=
te:
| >=20
| > | I've tested now int8(0) =3D=3D int16(0) and isequal(int8(0),int16=
(0)) and
| > | these don't work. From documentation, I believe that MATLAB answe=
rs 1 to
| > | both.
| > |=20
| > |=20
| > | octave:164> int8(0)=3D=3Dint16(0)
| > | error: binary operator `=3D=3D' not implemented for `int8 scalar'=
 by `int16
| > | scalar' operations
| >=20
| > | octave:164> isequal(int8(0),int16(0))
| > | error: can't perform indexing operations for int8 scalar type
| >=20
| > I've just checked in a set of changes that makes these (and many ot=
her
| > similar mixed-type) operations work as you would expect.
|=20
| I noticed the comment about 64-bit types in the code, but what happen=
s
| with an example like=20
|=20
| intmax("uint64") - uint64(1) =3D=3D intmax("uint64")
|=20
| casting to double before comparing will ensure that the above stateme=
nt
| returns true when it should return false...

Yes, I know it is not correct.  We need specializations for the int64
types.  It is a bit tricky.  What is the proper way to compare int64
and uint64 so that you always get the correct result=3F  I'd also like
to avoid warnings from gcc about possible wrong results due to
comparison of signed and unsigned types, even if that path through the
code is not actually possible.  I could not see a good way to do that.

jwe



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