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digitalmars.D - opCmp function

reply "Bruno A. Costa" <bruno codata.com.br> writes:
Hi all,

I was playing with D operator overloading and I found the opCmp function a
bit strange. Why the type returned is an int? It would not have to return a
bit?

And how should I code an opCmp overload? I tried the some coding (atached)
and it worked well, but I am not sure if the opCmp overloading (at the end)
is Ok.

Thanks,

Bruno.
May 03 2004
next sibling parent J Anderson <REMOVEanderson badmama.com.au> writes:
Bruno A. Costa wrote:


Hi all,

I was playing with D operator overloading and I found the opCmp function a
bit strange. Why the type returned is an int? It would not have to return a
bit?
  


opCmp returns 3 states

0: equal
-1: less then
1: more then



And how should I code an opCmp overload? I tried the some coding (atached)
and it worked well, but I am not sure if the opCmp overloading (at the end)
is Ok.



	int opCmp (Byte bt) {
		return (_value - bt.value);
	}


looks fine to me.


-- 
-Anderson: http://badmama.com.au/~anderson/
May 03 2004
prev sibling parent reply Ant <Ant_member pathlink.com> writes:
In article <c75vi8$2q14$1 digitaldaemon.com>, Bruno A. Costa says...

--nextPart1697271.eHQoPkZ5kg
Content-Type: text/plain; charset=iso-8859-1
Content-Transfer-Encoding: 8Bit

Hi all,

I was playing with D operator overloading and I found the opCmp function a
bit strange. Why the type returned is an int? It would not have to return a
bit?


0 means equal, <0 means one is lower, >0 means the other is lower.
(it's common practice)


And how should I code an opCmp overload? I tried the some coding (atached)
and it worked well, but I am not sure if the opCmp overloading (at the end)
is Ok.


I fell on that trap once so I should help now.
you must override int opComp(Object) not create a new int opComp(Byte)

So, are you doing an all OO lib? or just what you need?

Ant
May 03 2004
next sibling parent reply J Anderson <REMOVEanderson badmama.com.au> writes:
Ant wrote:


In article <c75vi8$2q14$1 digitaldaemon.com>, Bruno A. Costa says...
  


--nextPart1697271.eHQoPkZ5kg
Content-Type: text/plain; charset=iso-8859-1
Content-Transfer-Encoding: 8Bit

Hi all,

I was playing with D operator overloading and I found the opCmp function a
bit strange. Why the type returned is an int? It would not have to return a
bit?
    


0 means equal, <0 means one is lower, >0 means the other is lower.
(it's common practice)

  


And how should I code an opCmp overload? I tried the some coding (atached)
and it worked well, but I am not sure if the opCmp overloading (at the end)
is Ok.
    


I fell on that trap once so I should help now.
you must override int opComp(Object) not create a new int opComp(Byte)
  


class A
{
    byte val;

    int opCmp(A _a)
    {
      return val - _a.val;
    }   
}


int main ( char [] [] args )
{
    A a = new A;
    A b = new A;
   
    a.val = 10;
    b.val = 11;
   
    printf("%d < %d = %d\n", a.val, b.val, b < a);
}

This works.  What are you talking about?  You do need to do such things 
if you want to use sort with arrays (which I think is a bug). Other then 
that it should work fine.


So, are you doing an all OO lib? or just what you need?

Ant



  



-- 
-Anderson: http://badmama.com.au/~anderson/
May 03 2004
parent Ant <Ant_member pathlink.com> writes:
In article <c766ek$32u$1 digitaldaemon.com>, J Anderson says...

Ant wrote:


In article <c75vi8$2q14$1 digitaldaemon.com>, Bruno A. Costa says...
  


--nextPart1697271.eHQoPkZ5kg
Content-Type: text/plain; charset=iso-8859-1
Content-Transfer-Encoding: 8Bit

Hi all,

I was playing with D operator overloading and I found the opCmp function a
bit strange. Why the type returned is an int? It would not have to return a
bit?
    


0 means equal, <0 means one is lower, >0 means the other is lower.
(it's common practice)

  


And how should I code an opCmp overload? I tried the some coding (atached)
and it worked well, but I am not sure if the opCmp overloading (at the end)
is Ok.
    


I fell on that trap once so I should help now.
you must override int opComp(Object) not create a new int opComp(Byte)
  


class A
{
    byte val;

    int opCmp(A _a)
    {
      return val - _a.val;
    }   
}


int main ( char [] [] args )
{
    A a = new A;
    A b = new A;
   
    a.val = 10;
    b.val = 11;
   
    printf("%d < %d = %d\n", a.val, b.val, b < a);
}

This works.  What are you talking about?


Sorry, my mistake, I was talking about:

http://www.digitalmars.com/d/phobos.html#object

int cmp(Object obj) 

Compare with another Object obj. Returns: 
<0 for (this < obj) 
=0 for (this == obj) 

0 for (this > obj) 


Ant
May 03 2004
prev sibling parent "Bruno A. Costa" <bruno codata.com.br> writes:
Ant wrote:


 In article <c75vi8$2q14$1 digitaldaemon.com>, Bruno A. Costa says...

--nextPart1697271.eHQoPkZ5kg
Content-Type: text/plain; charset=iso-8859-1
Content-Transfer-Encoding: 8Bit

Hi all,

I was playing with D operator overloading and I found the opCmp function a
bit strange. Why the type returned is an int? It would not have to return
a bit?


 
 0 means equal, <0 means one is lower, >0 means the other is lower.
 (it's common practice)
 

And how should I code an opCmp overload? I tried the some coding (atached)
and it worked well, but I am not sure if the opCmp overloading (at the
end) is Ok.


 
 I fell on that trap once so I should help now.
 you must override int opComp(Object) not create a new int opComp(Byte)
 
 So, are you doing an all OO lib? or just what you need?
 
 Ant


I just wanted to learn D, so I started to write some easy wrappers to
primitive types. But an OO lib would be a very nice thing to do.

Bruno.
May 03 2004