Syntax help with Example 5.6 Migration to OPTMODEL: Generalized Networks

[user24feb]

Hello,

where can I find documentation regarding the "()"-brackets as in the node balancing restriction of example 5.6 (SAS/OR(R) 9.3 User's Guide: Mathematical Programming)?

con balance {i in NODES}:

      sum {<(i),j> in ARCS} Flow[i,j]

      - sum {<j,(i)> in ARCS} Flow[j,i]

      = _sd_;

Why this is necessary is quite clear; but can't find anything on this optmodel syntax.

Thanks & kind regards

[RobPratt · Accepted solution]

It is discussed in the "More on Index Sets" section of the PROC OPTMODEL documentation:

SAS/OR(R) 13.2 User's Guide: Mathematical Programming

See also this "Manpower Planning" example that shows three equivalent forms:

SAS/OR(R) 13.2 User's Guide: Mathematical Programming Examples

[LeoLopes]

It is a shorthand for the slice operator, often used to make this very common pattern:

    sum{<i,j> in FOO: i = something} x[i,j]

shorter, as in:

   sum{<(something),j> in FOO} x[something,j]