• bearophile (20/20) Jan 08 2013 How do you add contracts to delegates?
• Benjamin Thaut (4/24) Jan 08 2013 I don't think that this is possible at all. Do you think this is usefull...
• bearophile (14/16) Jan 08 2013 In a program I define a null delegate, then later I assign to it
• Dmitry Olshansky (9/23) Jan 08 2013 Then it has to be part of the type (a meta-info bound to it)... how
• bearophile (23/24) Jan 08 2013 In the first case the contracts are shared by all delegates, so

"bearophile" <bearophileHUGS lycos.com> writes:

How do you add contracts to delegates?

This doesn't work:


void main() {
     void delegate(int) foo;

     foo = (x)
     in {
         assert(x > 0);
     } body {
     };
}


Nor this:


void main() {
     void delegate(int) foo
     in {
         assert(x > 0);
     };

     foo = (x) {};
}

Bye,
bearophile

Benjamin Thaut <code benjamin-thaut.de> writes:

Am 08.01.2013 12:14, schrieb bearophile:
 How do you add contracts to delegates?

 This doesn't work:


 void main() {
      void delegate(int) foo;

      foo = (x)
      in {
          assert(x > 0);
      } body {
      };
 }


 Nor this:


 void main() {
      void delegate(int) foo
      in {
          assert(x > 0);
      };

      foo = (x) {};
 }

 Bye,
 bearophile

I don't think that this is possible at all. Do you think this is usefull?

Kind Regards
Benjamin Thaut

"bearophile" <bearophileHUGS lycos.com> writes:

Benjamin Thaut:

 I don't think that this is possible at all.

I see.


 Do you think this is usefull?

In a program I define a null delegate, then later I assign to it 
one of different functions according to some run time values, and 
later I call the delegate several times. In such situation a 
delegate is handy to shorten my code, where max performance is 
not needed.

I generally use contract programming, because I've seen it 
catches some of my coding mistakes. So what's wrong in desiring 
to add a pre-condition to that delegate? (Currently I have put 
the pre-condition asserts inside the function assigned to the 
delegate).

Bye,
bearophile

Dmitry Olshansky <dmitry.olsh gmail.com> writes:

08-Jan-2013 17:58, bearophile пишет:
 Benjamin Thaut:

 I don't think that this is possible at all.

 I see.


 Do you think this is usefull?

 In a program I define a null delegate, then later I assign to it one of
 different functions according to some run time values, and later I call
 the delegate several times. In such situation a delegate is handy to
 shorten my code, where max performance is not needed.

 I generally use contract programming, because I've seen it catches some
 of my coding mistakes. So what's

wrong in desiring to add a
 pre-condition to that delegate?

Then it has to be part of the type (a meta-info bound to it)... how 
would you then check if 2 functions have equivalent (but with different 
code) preconditions?

  (Currently I have put the pre-condition
 asserts inside the function assigned to the delegate).

Where it truly belongs.

 Bye,
 bearophile


-- 
Dmitry Olshansky

"bearophile" <bearophileHUGS lycos.com> writes:

Dmitry Olshansky:

 Then it has to be part of the type (a meta-info bound to it)...

In the first case the contracts are shared by all delegates, so 
there is no need for code equality:

void main() {
     void delegate(int x) foo
     in {
         assert(x > 0);
     };

     foo = (x) {};
}


If the contracts are attached to the function, can't you just 
trust the programmers to use compatible contracts, so again 
there's no need to compare code?

void main() {
     void delegate(int) foo;

     foo = (x)
     in {
         assert(x > 0);
     } body {
     };
}


Bye,
bearophile