On Monday, 7 November 2016 at 18:59:24 UTC, Jerry wrote:
On Monday, 7 November 2016 at 18:42:37 UTC, Picaud Vincent
wrote:
template isIntegralConstant(ANY)
{
enum bool
isIntegralConstant=__traits(identifier,ANY)=="IntegralConstant";
}
A bit more elegant way of doing that would be:
enum isIntegralConstant(T) = is(T : IntegralConstant!U, U...);
I would be very graceful for any help/advice that explains the
right way to implement C++ std::integral_constant<T,T value>
in the D language.
Vincent
Now the question is, do you really need IntegralConstant? I've
never used it in C++ so I don't really know any of the use
cases for it. But generally in D if you need something to be a
compile time constant value you can just use "enum". It can be
any type as well, so long as it can be evaluated at compile
time.
enum long someConstant = 1 << 32;
Hi Jerry,
Thank you so much for your quick answer! I tried your suggestion
and it works.
My main interest is numerical computations. I have some C++ libs
using meta-programming and I want to see how I can translate some
parts in D. The goal is to check: productivity & code readability
& performance. I will try to implement 2 toy examples:
1/ A basic example of strided dense vector structure dealing with
the dynamic/static size in an uniform way. In D I thing this can
be done with something like this (not tried yet to compile it,
but that is the idea to mimick my C++ implementation)
struct Vector(T,SIZE,STRIDE) if(
(is(SIZE==size_t)||isIntegralConstant!SIZE) ...)
{
alias T ElementType;
private SIZE size_;
private STRIDE stride_;
...
auto required_capacity() { return size_*stride_; } // return a
size_t or a IntegralConst
static if ( isIntegralConstant!(typeof(required_capacity()) )
{
}
else
{
}
}
