pointers, functions, and uniform call syntax

[Era Scarecrow]

On Wednesday, 5 September 2012 at 11:01:50 UTC, Artur Skawina 
wrote:
> On 09/04/12 20:19, Era Scarecrow wrote:
>>  I ask you, how do you check if it's a null pointer? &s?
>
> Yes, obviously. If you need to do that manually.
> 
>>   int getx(ref S s)
>>   //How does this make sense?? it looks wrong and is misleading
>>   in {assert(&s); }
>>   body {return s.x); }
>
> It looks correct and is perfectly obvious. But see below - you 
> don't need to do this manually - the compiler does it for you 
> when calling methods and could handle the UFCS case too.

  I've been thinking about this; It would definitely be the wrong 
thing to do. The assert would _Always_ succeed. The address you 
get would be of the pointer/reference for the stack (the pointer 
variable exists, where it points to isn't so much the case), so 
it would be the same as comparing it to this...

   int getx(S* s)
   in {assert(&s);} //always true, and always wrong.

  As I mentioned, it's wrong and is misleading. You'd have to work 
around the system to get the check correct; and even then if the 
compile decides to do something different you can only have it 
implementation dependent.

   int getx(ref S s)
   in {
     S *ptr = cast(S*) s;
     assert(ptr);
   }

  I'm not even sure this would even work (it's undefined 
afterall). I hope I never have to start adding such odd looking 
checks, else I would throw out ref and use pointers instead; At 
least with them the checks are straight-forward in comparison.