quirks of functions and delegates

[Ender KaShae]

Jarrett Billingsley Wrote:

> "Ender KaShae" <astrothayne at gmail.com> wrote in message 
> news:f8ghug$5bg$1 at digitalmars.com...
> 
> > 1.) when I try template t(type: function) I get an error, but there must 
> > be some way to specify that you need the type to be a function
> 
> template Templ(T : U function(V), U, V...)
> {
> 
> }
> 
> void main()
> {
>     mixin Templ!(int); // fails
>     mixin Templ!(void function(int, float)); // OK
> }
> 
> :)

I tried that, however when instantiating the template the return type and paramater tuple must be explicitly given, using a static if statement can be used to the same affect however
> 
> > 2.) in an example in the docs it says that arrays of functions are invalid 
> > types in c++ and d, however i've used arrays of function pointers in c++ 
> > and it seems strange that such a type would be invalid, a function pointer 
> > is after all just a pointer
> 
> There's a slight difference.  A function pointer is valid in both languages, 
> but a function type is illegal.  It's very difficult to get at a function 
> type in D, but possible.  Consider:
> 
> typedef void Foo();
> Foo[] f;
> 
> typedef void function() Bar;
> Bar[] g;
> 
> Notice that the first defines Foo as a function -- not function _pointer_ --  
> type.  Foo[] f; fails.  But the second defines Bar as a function pointer, 
> and Bar[] g is fine. 
> 
>