On Monday, 22 May 2017 at 21:44:17 UTC, ag0aep6g wrote:
On 05/22/2017 11:04 AM, Alex wrote:
[...]
Not only is a template not an lvalue, it's not any kind of
value at all. It doesn't have a type. You can't have a variable
holding a template. You can't pass it as an argument.
But a template is a symbol. You can pass it in an alias
parameter. So to pass dlg to C, you have to make C a template
with an alias parameter, like A is.
Aha... ok, I see...
[...]
`A!dlg a;` works. Calling `fun` doesn't.
A.fun instantiates dlg, resulting in a delegate that should be
able to access main's stuff. But it's not guaranteed that main
is active when A.fun is called. You could have returned `a`
from main before calling fun. For an actual delegate, a closure
would be made in that case. But dlg isn't a delegate, it's a
template. I guess it's not possible (or not feasible, or not
implemented) to create a closure a template like this.
ok, I see the point, I think...
If you don't actually need dlg to access main's stuff, you can
make it static. It's a function then and the delegate weirdness
doesn't apply.
yeah... no :)
the function inside the main has to have access to the main
stuff. Its the pointer inside C which could be static, if this
would help. So long, I go for the enhanced second variant...
For another approach to your problem, maybe have a look at
run-time variadic arguments:
https://dlang.org/spec/function.html#d_style_variadic_functions
With that kind of variadics, you're not dealing with a
template. A (run-time) variadic delegate is an actual delegate,
i.e. a value that can be passed around. But the variadic stuff
is a bit weird to use, and probably affects performance.
Hm... You are probably right... and variadic functions do not
really match the idea...
