Re: [eclipse-clp-users] Question regarding null variable

From: Kish Shen <kisshen_at_...5...>
Date: Mon, 15 Dec 2014 10:27:18 +0000
Hi Yogesh,

On 15/12/2014 08:32, Choughule, Yogesh wrote:
> Hi Kish
>
> I will explain null in Java context because i am trying to solve java code using ECLiPSe.
> for e.g.
> Integer x = null;
> In Java, null means variable x does not refer to any value in memory.
>

Prolog variables are quite different conceptually from variables in 
conventional programming languages. As Matthew said, Prolog variables 
are like variables in mathematics, in that they represent (as yet) 
unknown values when they are not instantiated. So conceptually, a 
variable is not a memory location to which you can assign values. This 
'variable as memory location' is made explicit in Java's null, and does 
not make sense in Prolog.

I am not sure what you mean by 'solve java code using ECLiPSe', but it 
does not look trivial and will probably involve a significant amount of 
programming in ECLiPSe, so again I suggest you should learn 
Prolog/ECLiPSe first.

Cheers,

Kish



> In Prolog, we write something like
> X $= 2,
>
> So in Prolog, i want to know if i can specify something like
> X $= null,
>
> if not, is there any similar concept which can be used as null in any of the libraries supported by ECLiPSe?
>
> Regards
>
> Yogesh
>
> ________________________________________
> From: Kish Shen [kisshen@...5...]
> Sent: 15 December 2014 17:00:58
> To: Choughule, Yogesh; eclipse-clp-users_at_lists.sourceforge.net
> Subject: Re: [eclipse-clp-users] Question regarding null variable
>
> Hi Yogesh,
>
> I think you need to give more context and explain what you mean by
> 'null'. ECLiPSe supports several constraint solver libraries -- so you
> need to say the library you are talking about for the 'constraint' you
> mentioned, and what exact effect 'null' has when 'specified as a
> constraint'.
> Cheers,
>
> Kish
>
> On 15/12/2014 01:52, Choughule, Yogesh wrote:
>> Dear Users
>>
>> My questions is regarding the usage of null variable.
>>
>> 1) Can we specify a variable as null in ECLiPSe?
>> I am trying to implement a functionality where null needs to be specified as a constraint.
>>
>> 2)if not, is there any workaround to represent null in ECLiPSe?
>>
>> Thanks and Regards
>>
>> Yogesh C.
>>
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>
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Received on Mon Dec 15 2014 - 10:27:50 CET

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