Jarrett Billingsley wrote:
> On Tue, Jun 30, 2009 at 11:38 AM, Jesse
> Phillips<[email protected]> wrote:
>> So looking at a post on StackOverflow about D gatchas:
>> http://stackoverflow.com/questions/743319/why-isnt-the-d-language-picking-up/1059780#1059780
>>
>> "functions that form closures or are attached to objects (ie. methods) are
>> not the same as regular functions, instead they are called delegates, and
>> you must be aware of the differences."
>>
>> I seem to recall the distinction was going to be going away or minimized. Is
>> this already done? Will it be going into D2?
>
> Nothing's changed in that area. Theoretically the compiler could
> implicitly convert function pointers to delegates by creating thunks.
> It shouldn't be *that* hard to implement..
Here's something I have in a project of mine. I didn't come up with the
idea, but I forget who did.
Note that this is not generalised. I started working on a general one,
but gave up when it proved too fiddly and difficult to correctly rebuild
a function's argument list.
/*
* This is utterly evil, but also REALLY cool.
*
* What we do here is make a dummy struct, and give it a member
* function. The member function has a hidden argument (this).
*
* We then construct a delegate of the appropriate type, set its
* funcptr to Wrap.call and its ptr to the function pointer.
*
* When dg is called, it is called as (dg.funcptr(dg.ptr, ...))
* which is the same way the (this) argument of member functions
* is passed.
*
* Thus, inside the member function, we can cast the this pointer
* back to our function pointer and call it.
*/
struct Wrap
{
void call(Context a, PullParserSlice b)
{
return (cast(void function(Context, PullParserSlice)) this)
(a,b);
}
}
ElementBinding.Handler dg;
Wrap wrap;
dg.ptr = handler;
dg.funcptr = cast(typeof(dg.funcptr)) &wrap.call;
