Problem with templates

[BCS]

Reply to Sean,

> BCS Wrote:
> 
>> Reply to Sean,
>> 
>>>> It can't.  Delegates and functions currently have different calling
>>>> conventions and the compiler cannot automatically convert one to
>>>> the other. Was this just intuition or did you read that it would
>>>> somewhere?
>>>> 
>>> Take this example:
>>> 
>> [...]
>> 
>>> void main()
>>> {
>>> int plus(int x, int y, int z)
>>> {
>>> return x + y + z;
>>> }
>>> auto plus_two = Curry(&plus, 2);
>>> Notice how the function Curry accepts a delegate, but a function
>>> pointer is actually passed in. I have personally re-written this
>>> function to take advantage of D2 closures and it worked perfectly
>>> fine.
>>> 
>> taking the address of a (non static) nested functions generates a
>> delegate, not a function pointer.
>> 
> I see. Any idea why this revised function still doesn't work?
> 
> R delegate(T) my_compose(R, IR, IT, T...)(IR function(T) first, R
> function(IT) second) {
> return delegate(T args) { return second(first(args)); };
> }
> test.d(40): template test.my_compose(R,IR,IT,T...) does not match any
> function template declaration
> 
> test.d(40): template test.my_compose(R,IR,IT,T...) cannot deduce
> template function from argument types !()(shortC  function(short,
> void*, void**),void function(short rc))
> 
> test.d(40): Error: function expected before (), not
> (my_compose(R,IR,IT,T...))((& SQLAllocHandle),(& SQL)) of type int
> 

I don't have time right now to dig out the context but... IFTI might just 
not be up to it.

you might try something like this

ReturnTypeOf!(S) delegate(ArgsOf!(F)) my_compose(F, S)(F first, S second)
{
  static assert(IsAFunctionType!(F)); // this might do better as a constraint
  static assert(IsAFunctionType!(S));
  return ReturnTypeOf!(S) delegate(ArgsOf!(F) args) { return second(first(args)); 
};
}

I'm sure you can find or write the used templates.

http://www.digitalmars.com/d/2.0/phobos/std_traits.html