On Wed, 09 Feb 2011 16:41:25 -0500, useo <[email protected]> wrote:
== Auszug aus bearophile ([email protected])'s Artikel
useo:
> I just have a problem with my variables.
>
> For example... my class/template just looks like:
>
> class Example(T) if (is(T == delegate) || is(T == function))
> {
> T callback;
>
> void setCallback(T cb) {
> callback = cb;
> }
>
> }
>
> This means that I need variables like Example!(void function
())
> myVariable. But is there any possibility to use variables like
> Example myVariable?
D is not the SML language, templates are just placeholders. If
you don't instantiate a template, you have only a symbol. Example
is only assignable to an alias (and in past, to a typedef):
alias Example Foo;
> The template declaration only defines the type of
> a callback and perhaps one method-declaration nothing else. I
already
> tried Example!(void*) because delegates and functions are void
> pointers but I always get an error. I hope there is any way
to do
> this.
I don't yet understand what you are trying to do.
Other notes:
- What if your T is a functor (a callable class/struct/union
instance that defined opCall)?
- sizeof of a function pointer is 1 CPU word, while a delegate
is 2 CPU words (and a delegate clojure has stuff on the heap too,
sometimes).
Bye,
bearophile
Idea is the following:
class Example(T) if (is(T == delegate) || is(T == function)) {
T callback;
void setCallback(T cb) {
callback = cb;
}
void opCall() {
callback();
}
}
other file:
import example;
private {
Example variable;
}
void setExampleVariable(Example ex) {
variable = ex;
}
void callCurrentExampleVariable() {
variable();
}
I don't think you want templates. What you want is a tagged union (and a
struct is MUCH better suited for this):
// untested!
struct Example
{
private
{
bool isDelegate;
union
{
void function() fn;
void delegate() dg;
}
}
void setCallback(void function() f) { this.fn = f; isDelegate = false;}
void setCallback(void delegate() d) { this.dg = d; isDelegate = true;}
void opCall()
{
if(isDelegate)
dg();
else
fn();
}
}
-Steve
