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D - Dernel: !== operator documentation missing

reply "=?iso-8859-1?Q?Robert_M._M=FCnch?=" <robert.muench robertmuench.de> writes:
Hi, I just found out (by pure chance) that there exists an !== operator,  
which seems to be for comparing objects or so. I couldn't find any  
documentation about this operator. Using != to compare objects bombs the  
kernel... Would be nice if this operator is added to the documentation.

-- 
Robert M. Münch
Management & IT Freelancer
http://www.robertmuench.de
Feb 24 2004
parent reply J C Calvarese <jcc7 cox.net> writes:
Robert M. Münch wrote:

 Hi, I just found out (by pure chance) that there exists an !== 
 operator,  which seems to be for comparing objects or so. I couldn't 
 find any  documentation about this operator. Using != to compare objects 
 bombs the  kernel... Would be nice if this operator is added to the 
 documentation.


When I first read you message, I though you were asking how these 
operators work. Now, I think I misunderstood the nature of your request, 
but I've included some information that might be helpful if someone 
wants to see an example regarding this issue.


[Comparing Objects]

I included an example that demonstrates some valid syntaxes for 
comparing objects. The recent addition of the "is" operator may explain 
any lack of mention of the older "===" operator. It's important to 
remember that these operators compare *references*, so that even if the 
values of the object properties are identical, false is returned as long 
as the references are different.


void main()
{ 	
   Object o, p;
		
		
   /* o and p are instantiated as separate (different) objects. */
   o = new Object();
   p = new Object();
	
	
   if(o is p) printf("o and p are references to the same object.\n");
   else printf("o and p are different objects.\n");

   if(!(o is p)) printf("They're not the same.\n");
   else printf("Yes, o is the same reference as p!\n");

   if(o === p) printf("o and p are references to the same object.\n");
   else printf("o and p are different objects.\n");

   if(!(o === p)) printf("They're not the same.\n");
   else printf("Yes, o is the same reference as p!\n");

   if(o !== p) printf("They're not the same.\n");
   else printf("Yes, o is the same reference as p!\n");

	
   printf("\nNow I'm gong to make them the same...\n");
	
   delete p;
   o = p;  	/* Now they're the same. */
	
   if(o is p) printf("o and p are references to the same object.\n");
   else printf("o and p are different objects.\n");

   if(!(o is p)) printf("They're not the same.\n");
   else printf("Yes, o is the same referenceas p!\n");

   if(o === p) printf("o and p are references to the same object.\n");
   else printf("o and p are different objects.\n");

   if(!(o === p)) printf("They're not the same.\n");
   else printf("Yes, o is the same reference as p!\n");

   if(o !== p) printf("They're not the same.\n");
   else printf("Yes, o is the same reference as p!\n");
		
}

-- 
Justin
http://jcc_7.tripod.com/d/
Feb 24 2004
parent "=?iso-8859-1?Q?Robert_M._M=FCnch?=" <robert.muench robertmuench.de> writes:
On Tue, 24 Feb 2004 17:45:12 -0600, J C Calvarese <jcc7 cox.net> wrote:


 When I first read you message, I though you were asking how these  
 operators work.


Hi, I just searched for them at some other D code and reverse engineered  
the semantic.


 I included an example that demonstrates some valid syntaxes for  
 comparing objects. The recent addition of the "is" operator may explain  
 any lack of mention of the older "===" operator.


Thanks a lot for this info. I must have missed this, even I scanned thru  
the docs yesterday... BTW: The === operator is still used in some Phobos  
code. Robert
Feb 25 2004