Marvin Humphrey <[EMAIL PROTECTED]> writes:
>Greets,
>
>Some of the algorithms I'm working on need to use sentinel values,
>which I'd typically get from limits.h. Can I get away with this?
>
> U32 aU32 = ULONG_MAX;
> while (aU32 == ULONG_MAX) {
> /* try to change aU32...
> * ...
> */
> }
No.
You might be on a platform where 'unsigned long' was 64 bits,
and so ULONG_MAX was 0xffffffffffffffffL but perl's U32 (for unsigned 32)
was Configure-d as unsigned int so could never equal ULONG_MAX.
Or if you used UV you might be on a platfrom configured for a 64-bit
perl even though "unsigned long" was only 32-bits.
>
>Is there a "limits.h" analog for XS data types like U32, UV, STRLEN,
>etc?
No. Instead perl has had Configure find system types which are suitable
for each types needs.
So if you want sentinels either use system types
unsigned long aul = ULONG_MAX;
Limit your self to a possible subset of the type
const U32 U32_MAX = 0xffffffff;
but note that on a 64-bit machine it may be possible
that au32 > U32_MAX !
or
bool value_set = 0
U32 value = ~0;
while (!value_set)
{
...
value = something;
value_set = true;
}
>
>Marvin Humphrey
>Rectangular Research
>http://www.rectangular.com/
