I've read the docs and implemented size_t getHash, int opEquals(Object o) and int opCmp(Object o); but it still doesn't work.

The following code prints out: 2 2 1

Btw.: I tested (new Foo(1)) == (new Foo(1)) and it gives true,
(new Foo(1)) == (new Foo(2)) gives false.


void main()
{
	class Foo
	{
		uint i;
		this(uint i ) { this.i = i; }

		size_t getHash()
		{
			return this.i;
		}

		int opEquals(Object o)
		{
			auto t = cast(Foo) o;
			if(t is null) return false;
			return (this.i == t.i);
		}

		int opCmp(Object o)
		{
			return opEquals(o);
		}
	}

	uint[Foo] all;

	all[new Foo(1)] = 0;
	all[new Foo(2)] = 0;
	all[new Foo(2)] = 0;

	foreach(k, v; all)
	{
		Stdout(k.i).newline;
	}
}

"Moritz Warning" <moritzwarning@web.de> wrote in message news:g4r043$28f$1@digitalmars.com...
> I've read the docs and implemented size_t getHash, int opEquals(Object o)
> and int opCmp(Object o); but it still doesn't work.
>
> The following code prints out: 2 2 1
>
> Btw.: I tested (new Foo(1)) == (new Foo(1)) and it gives true,
> (new Foo(1)) == (new Foo(2)) gives false.
>
>
> void main()
> {
> class Foo
> {
> uint i;
> this(uint i ) { this.i = i; }
>
> size_t getHash()
> {
> return this.i;
> }
>
> int opEquals(Object o)
> {
> auto t = cast(Foo) o;
> if(t is null) return false;
> return (this.i == t.i);
> }
>
> int opCmp(Object o)
> {
> return opEquals(o);
> }
> }

You don't have opCmp implemented correctly.  opEquals returns true if they are equal, while opCmp returns 0.

It should be

int opCmp(Object o)
{
    auto t = cast(Foo)o;
    if(t is null)
        return 1;

    return i < t.i ? -1 : i > t.i ? 1 : 0;
}

"Jarrett Billingsley" <kb3ctd2@yahoo.com> wrote in message news:g4r1c5$8b9$1@digitalmars.com...
> "Moritz Warning" <moritzwarning@web.de> wrote in message news:g4r043$28f$1@digitalmars.com...
>> I've read the docs and implemented size_t getHash, int opEquals(Object o)
>> and int opCmp(Object o); but it still doesn't work.
>>
>> The following code prints out: 2 2 1
>>
>> Btw.: I tested (new Foo(1)) == (new Foo(1)) and it gives true,
>> (new Foo(1)) == (new Foo(2)) gives false.
>>
>>
>> void main()
>> {
>> class Foo
>> {
>> uint i;
>> this(uint i ) { this.i = i; }
>>
>> size_t getHash()
>> {
>> return this.i;
>> }

And, it's supposed to be "toHash", not "getHash".  This is just where "override" comes in handy.

On Sun, 06 Jul 2008 22:02:44 +0400, Jarrett Billingsley <kb3ctd2@yahoo.com> wrote:

> "Moritz Warning" <moritzwarning@web.de> wrote in message
> news:g4r043$28f$1@digitalmars.com...
>> I've read the docs and implemented size_t getHash, int opEquals(Object o)
>> and int opCmp(Object o); but it still doesn't work.
>>
>> The following code prints out: 2 2 1
>>
>> Btw.: I tested (new Foo(1)) == (new Foo(1)) and it gives true,
>> (new Foo(1)) == (new Foo(2)) gives false.
>>
>>
>> void main()
>> {
>> class Foo
>> {
>> uint i;
>> this(uint i ) { this.i = i; }
>>
>> size_t getHash()
>> {
>> return this.i;
>> }
>>
>> int opEquals(Object o)
>> {
>> auto t = cast(Foo) o;
>> if(t is null) return false;
>> return (this.i == t.i);
>> }
>>
>> int opCmp(Object o)
>> {
>> return opEquals(o);
>> }
>> }
>
> You don't have opCmp implemented correctly.  opEquals returns true if they
> are equal, while opCmp returns 0.
>
> It should be
>
> int opCmp(Object o)
> {
>     auto t = cast(Foo)o;
>     if(t is null)
>         return 1;
>
>     return i < t.i ? -1 : i > t.i ? 1 : 0;
> }
>
>

Slightly offtopic, but shouldn't we have some function (in std.intrinsic, perhaps) to do just that:

int compare(int a, int b) {	// + overloads for byte, ubyte, short, ushort, uint, long, ulong
	return a < b ? -1 : a > b ? 1 : 0;
}

Jarrett Billingsley wrote:
> "Moritz Warning" <moritzwarning@web.de> wrote in message news:g4r043$28f$1@digitalmars.com...
>> I've read the docs and implemented size_t getHash, int opEquals(Object o)
>> and int opCmp(Object o); but it still doesn't work.
>>
>> The following code prints out: 2 2 1
>>
>> Btw.: I tested (new Foo(1)) == (new Foo(1)) and it gives true,
>> (new Foo(1)) == (new Foo(2)) gives false.
>>
>>
>> void main()
>> {
>> class Foo
>> {
>> uint i;
>> this(uint i ) { this.i = i; }
>>
>> size_t getHash()
>> {
>> return this.i;
>> }
>>
>> int opEquals(Object o)
>> {
>> auto t = cast(Foo) o;
>> if(t is null) return false;
>> return (this.i == t.i);
>> }
>>
>> int opCmp(Object o)
>> {
>> return opEquals(o);
>> }
>> }
> 
> You don't have opCmp implemented correctly.  opEquals returns true if they are equal, while opCmp returns 0.
> 
> It should be
> 
> int opCmp(Object o)
> {
>     auto t = cast(Foo)o;
>     if(t is null)
>         return 1;
> 
>     return i < t.i ? -1 : i > t.i ? 1 : 0;
> } 
> 
> 

Or just

int opCmp(Object o)
{
    auto t = cast(Foo)o;
    if(t is null)
        return 1;

    return i - t.i;
}

-Joel

On Sun, 06 Jul 2008 14:02:44 -0400, Jarrett Billingsley wrote:

> "Moritz Warning" <moritzwarning@web.de> wrote in message news:g4r043$28f$1@digitalmars.com...
>> I've read the docs and implemented size_t getHash, int opEquals(Object
>> o) and int opCmp(Object o); but it still doesn't work.
>>
>> The following code prints out: 2 2 1
>>
>> Btw.: I tested (new Foo(1)) == (new Foo(1)) and it gives true, (new
>> Foo(1)) == (new Foo(2)) gives false.
>>
>>
>> void main()
>> {
>> class Foo
>> {
>> uint i;
>> this(uint i ) { this.i = i; }
>>
>> size_t getHash()
>> {
>> return this.i;
>> }
>>
>> int opEquals(Object o)
>> {
>> auto t = cast(Foo) o;
>> if(t is null) return false;
>> return (this.i == t.i);
>> }
>>
>> int opCmp(Object o)
>> {
>> return opEquals(o);
>> }
>> }
> 
> You don't have opCmp implemented correctly.  opEquals returns true if they are equal, while opCmp returns 0.
> 
> It should be
> 
> int opCmp(Object o)
> {
>     auto t = cast(Foo)o;
>     if(t is null)
>         return 1;
> 
>     return i < t.i ? -1 : i > t.i ? 1 : 0;
> }

Thanks for spotting the bug. :)

On Sun, 06 Jul 2008 22:26:46 +0400, JAnderson <ask@me.com> wrote:

> Jarrett Billingsley wrote:
>> "Moritz Warning" <moritzwarning@web.de> wrote in message news:g4r043$28f$1@digitalmars.com...
>>> I've read the docs and implemented size_t getHash, int opEquals(Object o)
>>> and int opCmp(Object o); but it still doesn't work.
>>>
>>> The following code prints out: 2 2 1
>>>
>>> Btw.: I tested (new Foo(1)) == (new Foo(1)) and it gives true,
>>> (new Foo(1)) == (new Foo(2)) gives false.
>>>
>>>
>>> void main()
>>> {
>>> class Foo
>>> {
>>> uint i;
>>> this(uint i ) { this.i = i; }
>>>
>>> size_t getHash()
>>> {
>>> return this.i;
>>> }
>>>
>>> int opEquals(Object o)
>>> {
>>> auto t = cast(Foo) o;
>>> if(t is null) return false;
>>> return (this.i == t.i);
>>> }
>>>
>>> int opCmp(Object o)
>>> {
>>> return opEquals(o);
>>> }
>>> }
>>  You don't have opCmp implemented correctly.  opEquals returns true if they are equal, while opCmp returns 0.
>>  It should be
>>  int opCmp(Object o)
>> {
>>     auto t = cast(Foo)o;
>>     if(t is null)
>>         return 1;
>>      return i < t.i ? -1 : i > t.i ? 1 : 0;
>> }
>
> Or just
>
> int opCmp(Object o)
> {
>      auto t = cast(Foo)o;
>      if(t is null)
>          return 1;
>
>      return i - t.i;
> }
>
> -Joel

Be careful, it is fast but gives wrong result when comparing int.min and int.max!
I personally think that opCmp should return -1, 0 or 1 *only*. That's both safer and allows more advanced tricks.

Koroskin Denis wrote:
> On Sun, 06 Jul 2008 22:26:46 +0400, JAnderson <ask@me.com> wrote:
> 
>> Jarrett Billingsley wrote:
>>> "Moritz Warning" <moritzwarning@web.de> wrote in message news:g4r043$28f$1@digitalmars.com...
>>>> I've read the docs and implemented size_t getHash, int opEquals(Object o)
>>>> and int opCmp(Object o); but it still doesn't work.
>>>>
>>>> The following code prints out: 2 2 1
>>>>
>>>> Btw.: I tested (new Foo(1)) == (new Foo(1)) and it gives true,
>>>> (new Foo(1)) == (new Foo(2)) gives false.
>>>>
>>>>
>>>> void main()
>>>> {
>>>> class Foo
>>>> {
>>>> uint i;
>>>> this(uint i ) { this.i = i; }
>>>>
>>>> size_t getHash()
>>>> {
>>>> return this.i;
>>>> }
>>>>
>>>> int opEquals(Object o)
>>>> {
>>>> auto t = cast(Foo) o;
>>>> if(t is null) return false;
>>>> return (this.i == t.i);
>>>> }
>>>>
>>>> int opCmp(Object o)
>>>> {
>>>> return opEquals(o);
>>>> }
>>>> }
>>>  You don't have opCmp implemented correctly.  opEquals returns true if they are equal, while opCmp returns 0.
>>>  It should be
>>>  int opCmp(Object o)
>>> {
>>>     auto t = cast(Foo)o;
>>>     if(t is null)
>>>         return 1;
>>>      return i < t.i ? -1 : i > t.i ? 1 : 0;
>>> }
>>
>> Or just
>>
>> int opCmp(Object o)
>> {
>>      auto t = cast(Foo)o;
>>      if(t is null)
>>          return 1;
>>
>>      return i - t.i;
>> }
>>
>> -Joel
> 
> Be careful, it is fast but gives wrong result when comparing int.min and int.max!
> I personally think that opCmp should return -1, 0 or 1 *only*. That's both safer and allows more advanced tricks.

True, but at least in my line of work using values in the min/max range is rare and you can always do something different if your using byte or unsigned.  Having to branch during this sort of operation can be very expensive since it can live in the innermost of loops.

-Joel

JAnderson wrote:
> Koroskin Denis wrote:
>> On Sun, 06 Jul 2008 22:26:46 +0400, JAnderson <ask@me.com> wrote:
>>
>>> Jarrett Billingsley wrote:
>>>> "Moritz Warning" <moritzwarning@web.de> wrote in message news:g4r043$28f$1@digitalmars.com...
>>>>> I've read the docs and implemented size_t getHash, int opEquals(Object o)
>>>>> and int opCmp(Object o); but it still doesn't work.
>>>>>
>>>>> The following code prints out: 2 2 1
>>>>>
>>>>> Btw.: I tested (new Foo(1)) == (new Foo(1)) and it gives true,
>>>>> (new Foo(1)) == (new Foo(2)) gives false.
>>>>>
>>>>>
>>>>> void main()
>>>>> {
>>>>> class Foo
>>>>> {
>>>>> uint i;
>>>>> this(uint i ) { this.i = i; }
>>>>>
>>>>> size_t getHash()
>>>>> {
>>>>> return this.i;
>>>>> }
>>>>>
>>>>> int opEquals(Object o)
>>>>> {
>>>>> auto t = cast(Foo) o;
>>>>> if(t is null) return false;
>>>>> return (this.i == t.i);
>>>>> }
>>>>>
>>>>> int opCmp(Object o)
>>>>> {
>>>>> return opEquals(o);
>>>>> }
>>>>> }
>>>>  You don't have opCmp implemented correctly.  opEquals returns true if they are equal, while opCmp returns 0.
>>>>  It should be
>>>>  int opCmp(Object o)
>>>> {
>>>>     auto t = cast(Foo)o;
>>>>     if(t is null)
>>>>         return 1;
>>>>      return i < t.i ? -1 : i > t.i ? 1 : 0;
>>>> }
>>>
>>> Or just
>>>
>>> int opCmp(Object o)
>>> {
>>>      auto t = cast(Foo)o;
>>>      if(t is null)
>>>          return 1;
>>>
>>>      return i - t.i;
>>> }
>>>
>>> -Joel
>>
>> Be careful, it is fast but gives wrong result when comparing int.min and int.max!
>> I personally think that opCmp should return -1, 0 or 1 *only*. That's both safer and allows more advanced tricks.
> 
> True, but at least in my line of work using values in the min/max range is rare and you can always do something different if your using byte or unsigned.  Having to branch during this sort of operation can be very expensive since it can live in the innermost of loops.

Probably in most any line of work if you're getting within a factor of two of the max int then you are asking for trouble.

But I think the bigger issue is that precisely because you will never hit int.max or int.min, these values are often used as special indicator values.  Like to mean "not found" or "not initialized" or somesuch.

--bb

Bill Baxter wrote:
> JAnderson wrote:
>> Koroskin Denis wrote:
>>> On Sun, 06 Jul 2008 22:26:46 +0400, JAnderson <ask@me.com> wrote:
>>>
>>>> Jarrett Billingsley wrote:
>>>>> "Moritz Warning" <moritzwarning@web.de> wrote in message news:g4r043$28f$1@digitalmars.com...
>>>>>> I've read the docs and implemented size_t getHash, int opEquals(Object o)
>>>>>> and int opCmp(Object o); but it still doesn't work.
>>>>>>
>>>>>> The following code prints out: 2 2 1
>>>>>>
>>>>>> Btw.: I tested (new Foo(1)) == (new Foo(1)) and it gives true,
>>>>>> (new Foo(1)) == (new Foo(2)) gives false.
>>>>>>
>>>>>>
>>>>>> void main()
>>>>>> {
>>>>>> class Foo
>>>>>> {
>>>>>> uint i;
>>>>>> this(uint i ) { this.i = i; }
>>>>>>
>>>>>> size_t getHash()
>>>>>> {
>>>>>> return this.i;
>>>>>> }
>>>>>>
>>>>>> int opEquals(Object o)
>>>>>> {
>>>>>> auto t = cast(Foo) o;
>>>>>> if(t is null) return false;
>>>>>> return (this.i == t.i);
>>>>>> }
>>>>>>
>>>>>> int opCmp(Object o)
>>>>>> {
>>>>>> return opEquals(o);
>>>>>> }
>>>>>> }
>>>>>  You don't have opCmp implemented correctly.  opEquals returns true if they are equal, while opCmp returns 0.
>>>>>  It should be
>>>>>  int opCmp(Object o)
>>>>> {
>>>>>     auto t = cast(Foo)o;
>>>>>     if(t is null)
>>>>>         return 1;
>>>>>      return i < t.i ? -1 : i > t.i ? 1 : 0;
>>>>> }
>>>>
>>>> Or just
>>>>
>>>> int opCmp(Object o)
>>>> {
>>>>      auto t = cast(Foo)o;
>>>>      if(t is null)
>>>>          return 1;
>>>>
>>>>      return i - t.i;
>>>> }
>>>>
>>>> -Joel
>>>
>>> Be careful, it is fast but gives wrong result when comparing int.min and int.max!
>>> I personally think that opCmp should return -1, 0 or 1 *only*. That's both safer and allows more advanced tricks.
>>
>> True, but at least in my line of work using values in the min/max range is rare and you can always do something different if your using byte or unsigned.  Having to branch during this sort of operation can be very expensive since it can live in the innermost of loops.
> 
> Probably in most any line of work if you're getting within a factor of two of the max int then you are asking for trouble.
> 
> But I think the bigger issue is that precisely because you will never hit int.max or int.min, these values are often used as special indicator values.  Like to mean "not found" or "not initialized" or somesuch.

This is true.  Its difficult to imagine many cases with int where people want to use the entire range of signed int for a container.  Maybe if they are storing a mask or something.  I guess a healthy dose of asserts would be handy.

> 
> --bb