Vincent Lefevre <vincent-o...@vinc17.net> wrote:
> On 2018-07-23 08:06:46 +0000, Schwarz, Konrad wrote:
> > I don't think such code (to detect whether an arbitrary type is
> > signed or unsigned) exists.
>
> For the signness, one can just do: (T) -1 < 0
>
> Then, to get the minimum value of a signed type, assuming
> two's complement and no padding bits:
>
> (2 * -((T) 1 << (sizeof(T) * CHAR_BIT - 2)))
>
> as said in the message I've posted a few days ago.
You can even check the hardware type.....
On thursday, I changed my code to:
#define TYPE_ISSIGNED(t) (((t)-1) < ((t)0))
#define TYPE_ISUNSIGNED(t) (!TYPE_ISSIGNED(t))
#if (-3 & 3) == 1 /* Two's complement */
#define TYPE_MSBVAL(t) (2 * -(((t)1) << (sizeof (t)*CHAR_BIT - 2)))
#else
#define TYPE_MSBVAL(t) ((t)(~((t)0) << (sizeof (t)*CHAR_BIT - 1)))
#endif
#define TYPE_MINVAL(t) (TYPE_ISSIGNED(t) \
? TYPE_MSBVAL(t) \
: ((t)0))
#define TYPE_MAXVAL(t) ((t)(~((t)0) - TYPE_MINVAL(t)))
As a hint, you may use:
#if (-3 & 3) == 1
two's complement
#elif (-3 & 3) == 0
one's complement
#elif (-3 & 3) == 3
magnitude type
#endif
Jörg
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EMail:jo...@schily.net (home) Jörg Schilling D-13353 Berlin
joerg.schill...@fokus.fraunhofer.de (work) Blog: http://schily.blogspot.com/
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