>> 2) I have a restriction of the form
>> s.t. Rb{v1 in V,v2 in V: v1<v2}: ...
>> This works, if V contains numbers. If V contains symbols, v1<v2 is not
>> allowed.
>> Is there a function to convert symbols to their position in the set or
>> something like that?
>
> Yes, this is explained in the discussion of "ordered sets" in Section 5.6 of
> the AMPL book. If you don't have the book, you may be able to figure out
> what you need by looking at the following example:
>
> www.ampl.com/BOOK/EXAMPLES/steelT2.mod
> www.ampl.com/BOOK/EXAMPLES/steelT2.dat
Unfortunately "ordered sets" are not implemented in MathProg.
(The reason was that the AMPL implementation seems to be very
artificial. Introducing a binary relation between set's elements could
be more natural way, however, this feature is incompatible with AMPL.)
Andrew Makhorin
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