Class ElementVariable

All Implemented Interfaces:
SatisfiedPresent, Stateful, UsesQueueVariable

public class ElementVariable extends Constraint implements UsesQueueVariable, Stateful, SatisfiedPresent
ElementVariable constraint defines a relation list[index - indexOffset] = value.

The first element of the list corresponds to index - indexOffset = 1. By default indexOffset is equal 0 so first value within a list corresponds to index equal 1.

If index has a domain from 0 to list.length-1 then indexOffset has to be equal -1 to make addressing of list array starting from 1.

Version:
4.10
  • Field Details

    • idNumber

      static AtomicInteger idNumber
    • firstConsistencyCheck

      boolean firstConsistencyCheck
    • firstConsistencyLevel

      int firstConsistencyLevel
    • index

      public IntVar index
      It specifies variable index within an element constraint list[index - indexOffset] = value.
    • value

      public IntVar value
      It specifies variable value within an element constraint list[index - indexOffset] = value.
    • indexOffset

      public final int indexOffset
      It specifies indexOffset within an element constraint list[index - indexOffset] = value.
    • list

      public IntVar[] list
      It specifies list of variables within an element constraint list[index - indexOffset] = value. The list is addressed by positive integers (>=1) if indexOffset is equal to 0.
    • indexHasChanged

      boolean indexHasChanged
    • indexRange

      IntDomain indexRange
    • variableQueue

      LinkedHashSet<IntVar> variableQueue
    • mapping

      Map<IntVar,Integer> mapping
    • duplicates

      Map<IntVar,List<Integer>> duplicates
    • supports

      IntDomain[] supports
    • valueHasChanged

      private boolean valueHasChanged
    • generator

      Random generator
  • Constructor Details

    • ElementVariable

      public ElementVariable(IntVar index, IntVar[] list, IntVar value, int indexOffset)
      It constructs an element constraint.
      Parameters:
      index - variable index
      list - list of variables from which an index-th element is taken
      value - a value of the index-th element from list
      indexOffset - shift applied to index variable.
    • ElementVariable

      public ElementVariable(IntVar index, List<? extends IntVar> list, IntVar value)
      It constructs an element constraint.
      Parameters:
      index - variable index
      list - list of variables from which an index-th element is taken
      value - a value of the index-th element from list
    • ElementVariable

      public ElementVariable(IntVar index, List<? extends IntVar> list, IntVar value, int indexOffset)
      It constructs an element constraint.
      Parameters:
      index - variable index
      list - list of variables from which an index-th element is taken
      value - a value of the index-th element from list
      indexOffset - shift applied to index variable.
    • ElementVariable

      public ElementVariable(IntVar index, IntVar[] list, IntVar value)
      It constructs an element constraint.
      Parameters:
      index - variable index
      list - list of variables from which an index-th element is taken
      value - a value of the index-th element from list
  • Method Details

    • removeLevel

      public void removeLevel(int level)
      Description copied from interface: Stateful
      This function is called in case of the backtrack, so a constraint can clear the queue of changed variables which is no longer valid. This function is called *before* all timestamps, variables, mutablevariables have reverted to their previous value.
      Specified by:
      removeLevel in interface Stateful
      Parameters:
      level - the level which is being removed.
    • consistency

      public void consistency(Store store)
      Description copied from class: Constraint
      It is a (most probably incomplete) consistency function which removes the values from variables domains. Only values which do not have any support in a solution space are removed.
      Specified by:
      consistency in class Constraint
      Parameters:
      store - constraint store within which the constraint consistency is being checked.
    • getDefaultConsistencyPruningEvent

      public int getDefaultConsistencyPruningEvent()
      Specified by:
      getDefaultConsistencyPruningEvent in class Constraint
    • impose

      public void impose(Store store)
      Description copied from class: Constraint
      It imposes the constraint in a given store.
      Overrides:
      impose in class Constraint
      Parameters:
      store - the constraint store to which the constraint is imposed to.
    • queueVariable

      public void queueVariable(int level, Var var)
      Description copied from class: Constraint
      This is a function called to indicate which variable in a scope of constraint has changed. It also indicates a store level at which the change has occurred.
      Overrides:
      queueVariable in class Constraint
      Parameters:
      level - the level of the store at which the change has occurred.
      var - variable which has changed.
    • satisfied

      public boolean satisfied()
      Description copied from interface: SatisfiedPresent
      It checks if the constraint is satisfied. It can return false even if constraint is satisfied but not all variables in its scope are grounded. It needs to return true if all variables in its scope are grounded and constraint is satisfied.

      Implementations of this interface for constraints that are not PrimitiveConstraint may require constraint imposition and consistency check as a requirement to work correctly.

      Specified by:
      satisfied in interface SatisfiedPresent
      Returns:
      true if constraint is possible to verify that it is satisfied.
    • toString

      public String toString()
      Description copied from class: Constraint
      It produces a string representation of a constraint state.
      Overrides:
      toString in class Constraint