Value or Reference Semantics Trait

[John Colvin]

On Sunday, 12 January 2014 at 20:16:15 UTC, Nordlöw wrote:
> Is there a trait to check whether a type has value or reference 
> semantics?
>
> I need this in a template struct that adaptively (using static 
> if) represent histogram bins as either a dense static array or 
> a sparse associative array.

That's a complicated question in D. Only simple cases fit one or 
the other exactly.

E.g.
A class always has reference semantics, but may contain any 
combination of reference and value semantic fields.
A struct has value semantics, but may contain any combination of 
reference and value semantic fields.
A slice has value semantics w.r.t. its length and start point, 
but reference semantics for its data.
A static array has value semantics.

For your problem you should look at the set of IsSomething traits 
in the table at the top of 
http://dlang.org/phobos-prerelease/std_traits.html as they will 
hopefully be sufficient.