[Help-glpk] Help defining a set in AMPL

[Oswaldo Hernández]

Hello,

I am doing a research project on resource assignation and I am trying
to model it through AMPL but i have come upon a problem defining one
of my sets. I have the following sets described in AMPL:

set teachers;

set subjects;

set times; # Class times

set schedule within {t in teachers, s in subjects, t1 in times, t2 in times};
                            # This set is composed by all the
programmed classes
                            # during the academic period

And I would like to express a subset which contains back to back
classes (e.g. from 9 AM to 11 AM and then from 11 AM to 1 PM) taught
by a professor t. I would also like to be able to index this set by
professor. I have tried to express this set but I have had no luck.

Do any of you have an idea of how to do it?

Thanks in advance for all the help.

Best Regards.
Oswaldo Hernández.