send me some suggestion for a proper declaration of this variable
@variable(model, CHANGE[k in FAMILY, l in FAMILY, j in UNITS, t in TIME, t1 in TIME: k<>l and t+1=t1], Bin)
The problem is in k<>l (k must be different than l) and t+1=t1 (sequencing) - how is this properly stated in Julia/JuMP?
You need to use valid Julia syntax:
(k != l) && (t + 1 == t1)
Thank you odow.