| Proposed New AMPL Features | Draft of May 2?, 1997 |
- arg min {indexing-expr} object-expr
arg max {indexing-expr} object-expr
- Returns a member of the indexing-expr for which the minimum or maximum of the object-expr is achieved. In the case of ties, one arbitrarily selected member is returned. (Should there also be operators for determining the set of all members for which the min or max is achieved?)
- member_of {indexing-expr}
- unique_of {indexing-expr}
- Returns a member of the specified set. If the specified set has more than one member, member_of chooses one arbitrarily, whereas unique_of signals an error. An empty specified set is an error for either operator.
set CLIQUE {1..nCliques} within NODES
is sometimes loosely said to specify a "set of sets", in fact it
creates only a collection of sets CLIQUE[k] indexed over the
set of all k in 1..nCliques. To use such a
collection, it is necessary to define and use an underlying set
(1..nCliques in this case) that often is not an essential part
of the formulation. We describe below an extension to true sets of
sets, which are sets whose members are also sets. Then we describe and
discuss three models that could use this new feature to give a more
natural and direct formulation.More to come . . .
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