On Friday, 19 July 2013 at 17:51:29 UTC, Jonathan M Davis wrote:
On Friday, July 19, 2013 19:23:50 JS wrote:
On Friday, 19 July 2013 at 15:32:25 UTC, Jonathan M Davis
wrote:
> On Friday, July 19, 2013 11:06:26 JS wrote:
>> I would like to pass to all my templates the file and module
>> locations where they are used(this goes into a debugging
>> system I
>> have come up with).
>>
>> The problem is, with varadic types being passed I can't do
>> this:
>>
>> template T!(T..., string file = __FILE__)
>>
>> doesn't work.
>>
>> I think there is no way around except to explicitly pass
>> __FILE__... which would be a mess?
>
> As long as you're using a templated function and thus can use
> IFTI (implicit
> function template instantation) instead of giving the
> template
> arguments
> explicitly, you don't have to put the template parameters
> with
> default
> arguments last. You'd just have to put it after the variadic
> parameter if you
> intended to give the template arguments explicitly. So, as
> long
> as you don't
> have to give the template arguments explicitly, you're fine.
> If
> you need to
> give them explicitly though, I think that you're stuck.
>
> - Jonathan M Davis
I don't at all see how this could possibly work. The order of
parameters is crucial. With a type tuple it may be different
but
I just tried and it didn't work:
template A(string f = __FILE__, T...)
{
pragma(msg, f);
enum A = T.stringof;
}
called with A!(int, double) and got an error about argument
type
mismatch.
So unless you are talking about something else or there is some
"trick" involved I don't think this works...
As I said, it works if you're using IFTI (Implict Function
Template
Instantation) but not if you're giving the template arguments
explicitly. So,
if you're dealing with a templated function such as
auto foo(string file = __FILE__, T...)(T args) {...}
then it works. But if you're dealing with a template which is
not a function
(so you have to instantiate it explicitly), or you have to
instantiate the
templated function explicitly for any reason, then you'll be
forced to give
the file name as the first argument. So, you have a way out
with many templated
functions, but for other templates, you still have the problem
that you've
been running into.
- Jonathan M Davis
auto unique(T, string file = __FILE__, size_t line = __LINE__)(T
t)
{
return Unique!(T, file, line)(t);
}
Thanks, I just came across
https://github.com/PhilippeSigaud/D-templates-tutorial/blob/master/D-templates-tutorial.pdf
which has a lot of good info... I guess I didn't understand ITFI
at first... seems pretty powerful. I think I can use such a
function to solve the original problem I had.
Thanks again.
