Re: [eclipse-clp-users] On stating a strange constraint

[Panagiotis S. <ta...@di...>]

Hi Joachim,

First one is slightly more efficient than the second in my case.

Regards,
Panagiotis

On 29-Mar-23 11:20 AM, Joachim Schimpf via ECLiPSe-CLP-Users wrote:
> On 27/03/2023 10:51, Marco Gavanelli wrote:
>>
>> Anyway, what about:
>>
>> L[0] = 1
>>
>> forall i>0
>>      L[i] <= maxlist(L[0..(i-1)]) + 1
>> ?
>>
>> I hope the intuition is clear, with L[0..(1-i)] I mean the sublist of 
>> the first i elements of the list L.
> 
> 
> Here are two implementations, one of which may be faster in your 
> circumstances.
> 
> % version using max(List)
> precede1(Xs) :-
>          eval_to_array(Xs, Xz),
>          arity(Xz, N),
>          Xz #:: 1..N,
>          Xz[1] #= 1,
>          ( for(I,2,N), param(Xz) do
>              Xz[I] #=< max(Xz[1..I-1]) + 1
>          ).
> 
> % incremental version using max(Xi,Xj)
> precede2(Xs) :-
>          eval_to_array(Xs, Xz),
>          arity(Xz, N),
>          Xz #:: 1..N,
>          ( foreacharg(X,Xz), fromto(0,Max1,Max2,_) do
>              X #=< Max1 + 1,
>              Max2 #= max(Max1,X)
>          ).
> 
> 
> -- Joachim