On 2016-12-02 10:11, Ethan Watson wrote:
On Friday, 2 December 2016 at 08:33:17 UTC, Jacob Carlborg wrote:
But wWhat about an anonymous class as ag0aep6g mentioned?
Usability I see is something that is key here. Having to do a typeof
yourself is one extra step away from an intuitive API.
So I tried making a definition like this:
mixin template BitPack( Descriptor instance, string NameAlias =
Descriptor.stringof )
{
mixin( GenerateBitPackBody!( Descriptor, Descriptor.stringof )() );
}
...but I can't work out how to make the template evaluator treat
descriptor as a templated type without explicitly defining that type as
the first parameter.
Even trying:
mixin template BitPack( alias Descriptor ) if( is( typeof( Descriptor ) ) )
or:
mixin template BitPack( alias Descriptor ) if( __traits( compiles,
&Descriptor ) )
wasn't getting me valid code (in the case of the latter, it claims it's
not a valid template value argument; in the former, it meant I would
have needed to add additional constraints to the other BitPack template).
I bet there's a trick out there that'll let me do what I want. But I
won't go looking for it at least.
Using an alias without a template constraint works for me. No "typeof"
is required when using the template:
template Foo(alias T)
{
pragma(msg, __traits(identifier, T.tupleof[0]));
}
struct PackSize
{
int size;
}
void main()
{
mixin Foo!(
new class {
@PackSize( 3 ) int iSomeInt = 3;
@PackSize( 1 ) bool bSomeBool = true;
@PackSize( 4 ) int iSomeOtherInt;
}
);
}
The only difference now from your original example is "new class"
instead of "struct".
--
/Jacob Carlborg
