The following features are demonstrated in this example:
problem type: mixed integer linear programming (vehicle routing)
sets of tuples
sets indexed by other sets
set operators UNION and DIFF
INIT option
CARD function
using a colon (:) to select members of a set
AND aggregation operator
symmetry-breaking constraints
calling a solver in a DO UNTIL loop
row generation
connected components
.sol
variable suffix
CALL SYMPUT
SGPLOT procedure