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digitalmars.D - Re: Interfaces and Template Specializations

reply =?ISO-8859-1?Q?Bj=f6rn_T._Herzig?= <raichoo googlemail.com> writes:
 Go to the changelog.
 
 http://www.digitalmars.com/d/2.0/changelog.html



Thanks, downloaded the code but my testcode won't compile

void tester(U)(U u) if(is(U : Plugable) && is(U : Printable))
{
	writefln("U : Printable, Plugable");
	u.plug();
	u.print();
}

void tester(U)(U u)
{
	writefln("Nothing");
}

When calling tester with an object that implements Plugable and Printable it
complains that it matches more than one declaration of the template.

Regards,
Björn
Jan 10 2009
next sibling parent "Jarrett Billingsley" <jarrett.billingsley gmail.com> writes:
On Sat, Jan 10, 2009 at 8:51 PM, Bj=F6rn T. Herzig <raichoo googlemail.com>=
 wrote:

 Go to the changelog.

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



 Thanks, downloaded the code but my testcode won't compile

 void tester(U)(U u) if(is(U : Plugable) && is(U : Printable))



Try changing this to

void tester(U, DUMB=3Dvoid)(U u) if(is(U : Plugable) && is(U : Printable))

stupid compiler.
Jan 10 2009
prev sibling parent reply BCS <ao pathlink.com> writes:
Reply to Björn,


 Go to the changelog.
 
 http://www.digitalmars.com/d/2.0/changelog.html
 



 
 void tester(U)(U u) if(is(U : Plugable) && is(U : Printable))
 {
 writefln("U : Printable, Plugable");
 u.plug();
 u.print();
 }
 void tester(U)(U u)
 {
 writefln("Nothing");
 }
 When calling tester with an object that implements Plugable and
 Printable it complains that it matches more than one declaration of
 the template.
 
 Regards,
 Björn



try 

void tester(U)(U u) if(is(U : Plugable) && is(U : Printable))
 ...
void tester(U)(U u) if(is(U : Plugable) && !is(U : Printable))
 ...

or

void tester(U)(U u)
{
   static if(is(U : Plugable)) u.plug();
   static if(is(U : Printable)) u.print();
}

or something along that line
Jan 10 2009
parent reply =?ISO-8859-1?Q?Bj=f6rn_T._Herzig?= <raichoo googlemail.com> writes:
Content-Type: text/plain

BCS Wrote:


 
 try 
 
 void tester(U)(U u) if(is(U : Plugable) && is(U : Printable))
  ...
 void tester(U)(U u) if(is(U : Plugable) && !is(U : Printable))
  ...
 
 or
 
 void tester(U)(U u)
 {
    static if(is(U : Plugable)) u.plug();
    static if(is(U : Printable)) u.print();
 }
 
 or something along that line 
 
 



Thanks, the idea with negating some expressions came to me last night ^^. It
works.

So that would mean that if i would write something that is more specialized i
would have to negate every specialization for the default template?

void tester(U)(U u) if (is(U : Plugable) && is(U : Printable))
void tester(U)(U u) if (is(U : Plugable) && !is(U : Printable))
void tester(U)(U u) if (!is(U : Plugable) && is(U : Printable))
void tester(U)(U u) if (is(U : int) && !is(U : Plugable) && !is(U :Printable))
void tester(U)(U u) if (is(U : char) ..........)
//default template
void tester(U)(U u) if (!is(U : Plugable) && !is(U : Printable) && !is(U : int)
&& !is(U : char))
etc....

I tried this in a little piece of test code and i need to specialize so much
with every specialization i add, that the code becomes very unpleasant to write
(see attachment, it won't compile) 

Regards,
Björn
Jan 11 2009
parent Sergey Gromov <snake.scaly gmail.com> writes:
Sun, 11 Jan 2009 07:11:37 -0500, Björn T. Herzig wrote:


 So that would mean that if i would write something that is more
 specialized i would have to negate every specialization for the
 default template?
 
 void tester(U)(U u) if (is(U : Plugable) && is(U : Printable))
 void tester(U)(U u) if (is(U : Plugable) && !is(U : Printable))
 void tester(U)(U u) if (!is(U : Plugable) && is(U : Printable))
 void tester(U)(U u) if (is(U : int) && !is(U : Plugable) && !is(U :Printable))
 void tester(U)(U u) if (is(U : char) ..........)
 //default template
 void tester(U)(U u) if (!is(U : Plugable) && !is(U : Printable) && !is(U :
int) && !is(U : char))
 etc....
 
 I tried this in a little piece of test code and i need to specialize
 so much with every specialization i add, that the code becomes very
 unpleasant to write (see attachment, it won't compile) 



Maybe you should choose a different design then?  Use compile-time
polymorphism, you seem to do this anyway:

class Test
{
  void print() {...} // printable
}

class Test2
{
  void print() {...} // printable
  void plug() {...} // also pluggable
}

void tester(U)(U u)
{
  static if (!is(typeof(&u.print)))
  {
    static assert(false, "non-printable type");
  }
  else
  {
    static if (is(typeof(&u.plug)))
    {
      u.plug();
    }
    u.print();
  }
}

or maybe use run-time polymorphism--it's hard to tell from this toy case
which would be better for the actual task.
Jan 11 2009