The INTER aggregation operator evaluates the set-expression for each member of the index set index-set. The result is the set containing the intersection of the set of values that were returned by the set-expression for each member of the index set. An empty index set causes an expression evaluation error.

The following code uses the INTER aggregation operator to compute the value of {1,2,3,4} {2,3,4,5} {3,4,5,6}:

proc optmodel;
   put (inter{i in 1..3} i..i+3); /* outputs {3,4} */