Lindo Systems

MODEL:
SETS:
   TASKS: TIME, ES, LS, SLACK;
   PRED( TASKS, TASKS);
ENDSETS

DATA: 
   TASKS = @ODBC( 'PERTODBC', 'TASKS', 'TASKS');
   PRED = @ODBC( 'PERTODBC', 'PRECEDENCE', 'BEFORE', 'AFTER');
   TIME = @ODBC( 'PERTODBC');
   @ODBC( 'PERTODBC', 'SOLUTION', 'TASKS',
    'EARLIEST START', 'LATEST START') =
      TASKS, ES, LS;
ENDDATA

@FOR( TASKS( J)| J #GT# 1:
 ES( J) = @MAX( PRED( I, J): ES( I) + TIME( I))
);

@FOR( TASKS( I)| I #LT# LTASK:
 LS( I) = @MIN( PRED( I, J): LS( J) - TIME( I));
);

@FOR( TASKS( I): SLACK( I) = LS( I) - ES( I));

ES( 1) = 0;
LTASK = @SIZE( TASKS);
LS( LTASK) = ES( LTASK);
END