Re: [eclipse-users] Operators in Eclipse

Marconcini Cristina wrote:
> Dear All,
> 
> 
> I would like to submit you a question about the division operator in Eclipse.
> I am sorry because It should be trivial, but perhaps
> there is something that I haven't seen.
>  
> I need to perform a division with variables and get the integer quotient.
> In fact I will need to define a proper predicate like 
> div_pr(X,2,Y) where X is the dividend and Y the result.
> 
> I have tried this and I have loaded the ic library.
> 
> Yes (0.00s cpu)
> ?- Y :: 0 .. 5, X :: 0 .. 5, Y #= X / 2, X #= 1.
> No (0.00s cpu)

This is correct. The division here is standard division over
the reals, and it fails because Y is required to be integral,
and there is no integer solution for Y.

I guess you mean by "integer quotient" the quotient rounded
(down?) to the next integer?  You can define that as follows:

fdiv(Dividend, Divisor, Quotient, Remainder) :-
	Remainder #>=0, Remainder #< Divisor,
	Dividend #= Quotient*Divisor + Remainder.


?- [X, Y] :: 0 .. 5, fdiv(X, 2, Y, R).
X = X{0 .. 5}
Y = Y{0 .. 2}
R = R{[0, 1]}
There is 1 delayed goal.
Yes (0.00s cpu)

?- [X, Y] :: 0 .. 5, fdiv(X, 2, Y, R), X = 1.
X = 1
Y = 0
R = 1
Yes (0.01s cpu)


-- Joachim