On Monday, 7 November 2016 at 21:23:37 UTC, Picaud Vincent wrote:
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
{
}
}
Premature post send by error sorry.... Well something like:
static if ( isIntegralConstant!(typeof(required_capacity()) )
ElementType[required_capacity()] data_;
else
ElementType[] data_;
}
For that, at least in C++, I need integral_constant<> type with
compile-time arithmetic and smooth integration with "usual"
size_t/ptrdiff_t types.
2/ I also would like to test some implementations concerning
automatic differentiation.
I have my own C++ libs, inspired, but ~20% faster than Adept:
http://www.met.reading.ac.uk/clouds/adept/
and I would like to know how I can do that in D
Well... That is the idea... I hope I will get some results and I
will be happy to share if it is something interesting.
Vincent
