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digitalmars.D.learn - opEquals for same type

reply "deed" <none none.none> writes:
interface I
{
     // ...
     bool opEquals(I i);
}

class C : I
{
     // ...
     bool opEquals(I i)
     {
         return true;
     }
}

void main()
{
     I i1 = new C;
     I i2 = new C;
     assert(i1 == i2); // Assertion failure
     assert(i1 != i2); // Passes, although it's the opposite of 
what I want...
}

What's missing?
Dec 04 2012
parent reply =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
On 12/04/2012 04:12 PM, deed wrote:

 interface I
 {
 // ...
 bool opEquals(I i);
 }

 class C : I
 {
 // ...
 bool opEquals(I i)
 {
 return true;
 }
 }

 void main()
 {
 I i1 = new C;
 I i2 = new C;
 assert(i1 == i2); // Assertion failure
 assert(i1 != i2); // Passes, although it's the opposite of what I want...
 }

 What's missing?


opEquals is a special function of Object but interface's do not inherit 
from Object. Just override it on the class:

interface I
{
     // ...
     // bool opEquals(I i);
}

class C : I
{
     int i;

     // ...
     override bool opEquals(Object o) const
     {
         auto rhs = cast(const C)o;

         return (rhs && (i == rhs.i));
     }
}

void main()
{
     I i1 = new C;
     I i2 = new C;
     assert(i1 == i2);
}

What I know about this topic is in the following chapter:

   http://ddili.org/ders/d.en/object.html

Ali

-- 
D Programming Language Tutorial: http://ddili.org/ders/d.en/index.html
Dec 04 2012
parent "deed" <none none.void> writes:
 What I know about this topic is in the following chapter:

   http://ddili.org/ders/d.en/object.html

 Ali


Thanks, Ali. That clarifies why it worked with opCmp and not with 
opEquals.
Dec 05 2012