• Extrawurst (2/2) Mar 14 2008 - Functions returning Tuples -
• Russell Lewis (16/19) Mar 17 2008 While I look forward to the day when this is eventually supported by the...
• Koroskin Denis (46/48) Mar 17 2008 Functions return values, not types. You can use templates for this. An ...
• Koroskin Denis (3/3) Mar 17 2008 Well, I am wrong. There _IS_ a future direction to support returning

Extrawurst <spam extrawurst.org> writes:

- Functions returning Tuples -

Is this planned to be implemented in D2.x ?

Russell Lewis <webmaster villagersonline.com> writes:

Extrawurst wrote:
 - Functions returning Tuples -
 
 Is this planned to be implemented in D2.x ?

While I look forward to the day when this is eventually supported by the 
language, you can already do it by hand.  I have this common template 
which I include in my projects:

	struct Structize(TYPE_TUPLE)
	{
		TYPE_TUPLE fields;
	}

So you can do:
	Structize!(int,char) foo()
	{
		Structize!(int,char) ret;
		ret.fields[0] = 1234;
		ret.fields[1] = 'a';
		return ret;
	}

"Koroskin Denis" <2korden+dmd gmail.com> writes:

On Sat, 15 Mar 2008 05:33:07 +0300, Extrawurst <spam extrawurst.org> wro=
te:

 - Functions returning Tuples -

 Is this planned to be implemented in D2.x ?

Functions return values, not types. You can use templates for this. An  =

example from Phobos std.traits:

/***
  * Get the types of the paramters to a function,
  * a pointer to function, or a delegate as a tuple.
  * Example:
  * ---
  * import std.traits;
  * int foo(int, long);
  * void bar(ParameterTypeTuple!(foo));      // declares void bar(int,  =

long);
  * void abc(ParameterTypeTuple!(foo)[1]);   // declares void abc(long);=

  * ---
  */
template ParameterTypeTuple(alias dg)
{
     alias ParameterTypeTuple!(typeof(dg)) ParameterTypeTuple;
}

/** ditto */
template ParameterTypeTuple(dg)
{
     static if (is(dg P =3D=3D function))
	alias P ParameterTypeTuple;
     else static if (is(dg P =3D=3D delegate))
	alias ParameterTypeTuple!(P) ParameterTypeTuple;
     else static if (is(dg P =3D=3D P*))
	alias ParameterTypeTuple!(P) ParameterTypeTuple;
     else
	static assert(0, "argument has no parameters");
}

Now having any function pointer or a delegate you can get its arguments =
as  =

a tuple:

void testDelegate(DelegateType)(DelegateType dg)
{
     alias ParameterTypeTuple!(DelegateType) Arguments;

     // check that num args =3D=3D 2
     static assert(Arguments.length =3D=3D 2);

     // first param is an int
     static assert(is(Arguments[0] =3D=3D int));

     // second one is a reference type
     static assert(is(Arguments[0] : Object));

     dg(0, null);
}

"Koroskin Denis" <2korden+dmd gmail.com> writes:

Well, I am wrong. There _IS_ a future direction to support returning  
tuples from functions. :)

http://www.digitalmars.com/d/2.0/tuple.html