[Help-glpk] Indexing a subset from 1..n

[joel mortyn]

Hello all,

I have a set of Periods from which I create the subset OpenPeriods when the facility is open.

param nPeriods;

set Periods, default{1.. nPeriods};

param FacilityOpen{p in Periods}, binary;

set OpenPeriods:= setof{p in Periods: FacilityOpen[p] = 1}  (p);

The facility is not open during all periods and I have a constraint that considers the configuration of the facility the previous time it was open. So I am trying to index the set of OpenPeriods from 1...card(OpenPeriods) rather than with p but so far without any luck.

Any help would be much appreciated.

Thanks,

Joel