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Hello,

is there a signed datatype like the unsigned std::size_t? I think
std:trdiff_t is for pointer arithmetics. I need a type with the same
size but like a signed datatype.

Thanks

Phil

On 12/19/10 07:31 AM, Philipp Kraus wrote:
> Hello,
>
> is there a signed datatype like the unsigned std::size_t? I think
> std:trdiff_t is for pointer arithmetics. I need a type with the same
> size but like a signed datatype.

POSIX defines ssize_t, other systems may also have it. Other wise
define your own.

--
Ian Collins

Philipp Kraus <> wrote:
> is there a signed datatype like the unsigned std::size_t? I think
> std:trdiff_t is for pointer arithmetics. I need a type with the same
> size but like a signed datatype.

Not an answer to your question, but an additional question (related
to it):

Does the standard allow sizeof(std:trdiff_t) to be different from
sizeof(std::size_t)?

Juha Nieminen wrote:
> Philipp Kraus <> wrote:
>> is there a signed datatype like the unsigned std::size_t? I think
>> std:trdiff_t is for pointer arithmetics. I need a type with the
>> same size but like a signed datatype.
>
> Not an answer to your question, but an additional question (related
> to it):
>
> Does the standard allow sizeof(std:trdiff_t) to be different from
> sizeof(std::size_t)?

The standard doesn't say anything about that, except that they
shouldn't be larger than sizeof(unsigned long) unless specifically
needed.

If it isn't forbidden, it's probably allowed.



Bo Persson

On 2010-12-18 20:53:14 +0100, Ian Collins said:

> On 12/19/10 07:31 AM, Philipp Kraus wrote:
>> Hello,
>>
>> is there a signed datatype like the unsigned std::size_t? I think
>> std:trdiff_t is for pointer arithmetics. I need a type with the same
>> size but like a signed datatype.
>
> POSIX defines ssize_t, other systems may also have it. Other wise
> define your own.

Thanks for that answer. I know that POSIX defines this, but my code is
for cross-plattform, so I can't use the POSIX definition. I think I
will define my own type

Phil

On 20 déc, 12:26, Philipp Kraus <philipp.kr...@flashpixx.de> wrote:
> On 2010-12-18 20:53:14 +0100, Ian Collins said:
>
> > On 12/19/10 07:31 AM, Philipp Kraus wrote:
> >> Hello,
>
> >> is there a signed datatype like the unsigned std::size_t? I think
> >> std:trdiff_t is for pointer arithmetics. I need a type with the same
> >> size but like a signed datatype.
>
> > POSIX defines ssize_t, other systems may also have it. *Other wise
> > define your own.
>
> Thanks for that answer. I know that POSIX defines this, but my code is
> for cross-plattform, so I can't use the POSIX definition. I think I
> will define my own type

If your compilers supports some C++0x features, you can define:

typedef std::make_signed<size_t>::type ssize_t;

Or roll your own make_signed<>.

--
Michael

Article "About size_t and ptrdiff_t" - http://www.viva64.com/en/a/0050/