Repetition set members

[Josip.Lorincz ()]

Respected,
i have 2 questions:
1. is it possible in AMPL to generate ordered sets with repetition set members,
for example:
data;
set LINKS:= L1 L1 L2 L1 L3 L4 L2;

2. is it possible in AMPL to generate set of pairs of members which will be ordered, for example:
model;
set COSTUM ordered within {LP_PAIRS};

data;
set COSTUM := L1,P1 L1,P2 L2,P1 L2,P2;
Thanks in advance.
Best regards.
Josip