[BUG] Exception when running TeacherTimetable example

[TrevorDArcyEvans]

• Steps to reproduce

  • run TeacherTimetable example
  • get unhandled exception:

     at Decider.Csp.Integer.DomainBinaryInteger.get_InstantiatedValue() in /_/Csp/Integer/DomainBinaryInteger.cs:line 125
     at Decider.Csp.Integer.VariableInteger.get_InstantiatedValue() in /_/Csp/Integer/VariableInteger.cs:line 87
     at Decider.Csp.Integer.VariableInteger.get_Value() in /_/Csp/Integer/VariableInteger.cs:line 165
     at Decider.Example.TeacherTimetable.TeacherTimetable.Main() in /home/trevorde/dev/Decider/Examples/TeacherTimetable/TeacherTimetable.cs:line 97
  

• Observed result

  • unhandled exception
    • DeciderException("Trying to access InstantiatedValue of an uninstantiated domain.")
  • State.Search returns StateOperationResult.Unsatisfiable

• Expected result

  • no exceptions
  • example should be solvable

[TrevorDArcyEvans]

Looks like incorrect use of Aggregate

The following changes seem to fix it:

			// No teacher teaches more than 5 hours per weekday
			foreach (var teacher in Enumerable.Range(1, numberOfTeachers))
			{
				foreach (var day in Weekdays)
				{
					constraints.Add(new ConstraintInteger(
						new ExpressionInteger(day.
						Select(x => x == teacher).
						Count()) <= 5));
				}
			}

			// No teacher teaches more than 27 hours per week
			foreach (var teacher in Enumerable.Range(1, numberOfTeachers))
			{
				constraints.Add(new ConstraintInteger(
					new ExpressionInteger(Week.
					Select(x => x == teacher).
					Count()) <= 27));
			}