On 06/06/2012 05:33 PM, Era Scarecrow wrote:
> On Wednesday, 6 June 2012 at 20:52:14 UTC, bearophile wrote:
>> That seems correct, this works:
>>
>> template Foo(T) {
>> enum Foo {
>> bitsPerT = T.sizeof * 8,
>> }
>> }
>> void main() {
>> pragma(msg, Foo!int.bitsPerT);
>> }
>>
>>
>> So if template Foo(T){enum Foo{}} works, then I think it should also
>> work the enum Foo(T){} syntax.
>>
>> So far I don't think I have had to use templated enums, but if other
>> people have such need, than this thread and this post have enough
>> material for a little enhancement request.
>
> Well if it was only 1-2 value I wouldn't probably have bothered. However
> when there are several flags enums and values that are calculated based
> on eachother and used together; I wouldn't want to write enums manually
> for each type.
>
> Seems I'm being thrown now into the deep end of templates and
> constraints and traits and trying to fully understand it enough to use
> it all. What an exciting time to be alive :)
As far as I understand, this is all you need:
template bitsPer(T)
{
static if (is (T ClassType == class)) {
enum bitsPer = __traits(classInstanceSize, ClassType) * 8;
} else {
enum bitsPer = T.sizeof * 8;
}
}
class C
{
int[10] a;
}
void main()
{
static assert(bitsPer!byte == 8);
static assert(bitsPer!int == 32);
static assert(bitsPer!C == 448);
}
Other specializations of bitsPer may be needed.
Ali
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