Function to convert functions to delegates

[BCS]

Jarrett Billingsley wrote:
> I came up with this function to make it easier to make libraries that can 
> take function pointers or delegates for things like callbacks.  Basically it 
> creates a dummy struct to function as the context for the delegate, which 
> then calls the original function.  I guess that's a thunk?  Anyway:
> 
[...]
> 
> To use it, just make a function:
> 
> void func(int x, int y)
> {
>     writefln("func: ", x, ", ", y);
> }
> 
> And then call it:
> 
> auto dg = Delegatize!(func)();
> dg(4, 5); // prints "func: 4, 5"
> 

I guess that's a common thing to need to do. I wrote one of my own a 
while back. It trades a bit of a runtime hit (notice the new and 
assignment) for runtime flexibility (it can take a runtime function 
pointer).




T delegate(A) Fn2Dg(T, A...)(T function(A) f)
{
    struct tmp
    {
       typeof(f) fn;
       T ret(A args){ return fn(args); }
    };

    tmp* ret = new tmp;
    ret.fn = f;
    return &ret.ret;
}

char fn(int i, char j);
char delegate(int, char) dg = Fn2Dg(&fn);
char function(int, char) fp = &fn;
char delegate(int, char) dgr = Fn2Dg(fp);




It comes from my paper on D:
http://www.webpages.uidaho.edu/~shro822/term_008.pdf