$title Example: Use of subsets and previous els  in equation definitions

$onuellist


set I / A, B, 1*20 /;

* J declared to be a subset of I that doesn't contain its first two
* elements 
set J(I) / 1*20 /;

variable x(I), dummy_cost;

equation
	fibonacci(I)
	objective;

x.fx("A") = 1;
x.fx("B") = 1;

fibonacci(I)$J(I)..
	x(I) =e= x(I-1) + x(I-2);

objective..
	dummy_cost =e= 0;

model fib /all/;

solve fib using lp minimizing dummy_cost;

display x.l;

fib.holdfixed = 1;
solve fib using lp minimizing dummy_cost;