Re: [eclipse-clp-users] eplex: Unable to linearise / type error

From: Kish Shen <kisshen_at_...5...>
Date: Thu, 11 Sep 2008 15:42:18 +0100
Ulrich Scholz wrote:
> Thanks Joachim,
> 
> now this error went away.  Maybe you should note the predecence issue in the
> eplex description.  (Maybe you do and I missed it)
> 
> Best,
> 
> Ulrich
> 
> 
> On Thu, Sep 11, 2008 at 12:27:29AM +0100, Joachim Schimpf wrote:
>> Kish Shen wrote:
>>> Ulrich Scholz wrote:
>>>> Dear all,
>>>>
>>>> I try to write a CP problem with the eplex constraint solver.  Below you
>>>> find my code.
>>>>
>>>> I use decision variables to select one of a list of values.  On the call
>>>>
>>>>   :- generateSubcomponents(3, S). 
>>>>
>>>> I get the following error:
>>>>
>>>> Eplex warning: Unable to linearise my_instance : Utility =:= [3, 1, 6] * [_184, _186, _188]
>>>> type error in eplex : (my_instance : Utility =:= [3, 1, 6] * [_184, _186, _188])
>>>> Abort
>>>>
>> ...
>>>>     
>>>>     my_instance: Utility $= Utilities * DVs,
>>>>     
>>>>     Subcomponent = [Utility, DVs, Utilities].
>>>> --------------
>>>>
>>> Hi,
>>>
>>> You are not using the correct syntax -- you cannot simply use lists in 
>>> expression.
>>
>> Actually, the List*List syntax is legal in lib(eplex) and lib(ic).
>> The problem is the relative precedence of the : and the $= operator.
>> The : binds stronger than the $=, so you have to add parentheses like
>>
>>   my_instance:(Utility $= Utilities * DVs)
>>
>>
>> Cheers,
>> -- Joachim
> 
I don't think it is explicitly discussed in the eplex chapter, but all 
the descriptions for the constraints that need it are shown with brackets.

The problem is that it is easy to miss them when you are looking at the 
code, and the error messages you get when you don't use them is not too 
helpful. There is better error messages for the :: cases, and I will 
look to see if this can be done for the other constraints as well.

I will also add in some explicit mention of the brackets issue.

Cheers,

Kish

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Received on Thu Sep 11 2008 - 07:42:30 CEST

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