[eclipse-users] A problem constraining sets of real numbers

From: VicenÁ <vgomez_at_iua.upf.edu>
Date: Mon, 24 Sep 2007 12:34:12 +0200
Dear all,

I needed to constrain from above and below a sum of variables whose 
domains are sets of integer values. I did in that way, using the ic 
library. For instance:

X::[1,2,3],
Y::[0,1],
Z::[0,2],
X+Y+Z #< 6,
X+Y+Z #> 4,
writeln([X,Y,Z]),
labeling([X,Y,Z]).

fine. I got [X{[2, 3]}, Y{[0, 1]}, 2] after the writeln, since Z must be 
instantiated to 2 to fulfill the 2nd constraint.

But now, I would like to use sets of real numbers instead of integers. 
How is the proper method for doing an equivalent program? After loading 
lib(ic) and lib(propia), I declare the domains and use the $< and $> 
operators:

member(X,[1.0,2.0,3.0]) infers ic,
member(Y,[0.0,1.0]) infers ic,
member(Z,[0.0,2.0]) infers ic,
X+Y+Z $< 6.0,
X+Y+Z $> 4.0

after this, I got:

X = X{1.0 .. 3.0}
Y = Y{0.0 .. 1.0}
Z = Z{0.0 .. 2.0}
There are 5 delayed goals.
Yes (0.00s cpu)

Two questions:

1.- Why the domain of Z has not been reduced? What can I do to propagate 
the constraint?

2.- How can I force the instantiation of all the variables? If I use 
labeling([X,Y,Z]), I got the type error:

type error in indomain(X{1.0 .. 3.0})

many thanks,



   VicenÁ
Received on Mon Sep 24 2007 - 11:33:27 CEST

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