I am dealing with a discrete math optimization problem on a complete graph. My variables are the arcs but I want to delete the arcs that "cost too much". I have $n$ nodes which means I have $n(n-1)$ arcs before deletion. I define the following set in AMPL
ARCS:={i in 1..n, j in 1..n : i!=j && d[i,j]<= R}
where d[i,j] is the cost on the arc (i,j) and R the limit I am putting.
My problem is that I don't know how to index the variables now. I know I can write
sum{ i in 1..n, j in 1..n : (i,j) in ARCS} blablabla[i,j]
But I think this is quite a tedious way to do.
I thought I could write something like this
sum{e in ARCS} blablabla[e[0],e[1]]
