In reply to l87:
The dist construct is not really a hard constraint other than the fact that values with a probability of 0 or otherwise not mentioned are excluded (meaning the inside {[1:7}} constraint is redundant).
Without the sum constraint, the fixed value distribution you wrote with would produce an average of 4.4988 for each array element. Note that [1:2]:/5 is just a shortcut for writing 1:=2.5, 2:=2.5, not that an array element has a choice of having the value 1 or 2, with a combined weight of 5.