Hello everybody

I have a question about coding logical constraint in the GAMS IDE.

Please, let me describe optimization model:

{

set i /1*2/;

parameter cost(i);

integer variable nb(i);

…

of… obj =e= sum(i,cost(i)*nb(i))+(x-1)*500;

con1… sum(i,nb(i)*ns(i)) =g= N;

}

There is a logical constraint in the form below:

{

if(nb(i)<>0) then:

integer variable x;

x = sum(i,nb(i)); “x= sum of number of active variables, nb(1) & nb(2)”

}

logical constraint means that:

if nb(1)<>0 (and / or) nb(2)<>0 then:

x=0 or1 or 2; “that is sum of active variables not quantity of variables”.

Please, let me know, how can I define such a logical constraint?

Best regards

Omidi. A