Re: [Help-glpk] Questions to MathProg

[Andrew Makhorin]

>> 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