Class GeneralComparison

All Implemented Interfaces:
Serializable, SourceLocator, LocationProvider, SaxonLocator, CallableExpression, ComparisonExpression, InstructionInfo, Locator
Direct Known Subclasses:
GeneralComparison20

public class GeneralComparison extends BinaryExpression implements ComparisonExpression, CallableExpression
GeneralComparison: a boolean expression that compares two expressions for equals, not-equals, greater-than or less-than. This implements the operators =, !=, invalid input: '<', >, etc. This implementation is not used when in backwards-compatible mode
See Also:
  • Field Details

    • ONE_TO_ONE

      public static final int ONE_TO_ONE
      See Also:
    • MANY_TO_ONE

      public static final int MANY_TO_ONE
      See Also:
    • MANY_TO_MANY

      public static final int MANY_TO_MANY
      See Also:
    • singletonOperator

      protected int singletonOperator
    • comparer

      protected AtomicComparer comparer
    • needsRuntimeCheck

      protected boolean needsRuntimeCheck
    • comparisonCardinality

      protected int comparisonCardinality
  • Constructor Details

    • GeneralComparison

      public GeneralComparison(Expression p0, int op, Expression p1)
      Create a relational expression identifying the two operands and the operator
      Parameters:
      p0 - the left-hand operand
      op - the operator, as a token returned by the Tokenizer (e.g. Token.LT)
      p1 - the right-hand operand
  • Method Details

    • needsRuntimeCheck

      public boolean needsRuntimeCheck()
      Ask whether a runtime check of the types of the operands is needed
    • setNeedsRuntimeCheck

      public void setNeedsRuntimeCheck(boolean needsCheck)
      Say whether a runtime check of the types of the operands is needed
    • getComparisonCardinality

      public int getComparisonCardinality()
      Ask whether the comparison is known to be many-to-one, one-to-one, or many-to-many. (Note, an expression that is one-to-many will be converted to one that is many-to-one).
    • setComparisonCardinality

      public void setComparisonCardinality(int card)
      Say whether the comparison is known to be many-to-one, one-to-one, or many-to-many.
    • setAtomicComparer

      public void setAtomicComparer(AtomicComparer comparer)
      Set the comparer to be used
      Parameters:
      comparer - the comparer to be used
    • simplify

      public Expression simplify(ExpressionVisitor visitor) throws XPathException
      Description copied from class: BinaryExpression
      Simplify an expression
      Overrides:
      simplify in class BinaryExpression
      Parameters:
      visitor - an expression visitor
      Returns:
      the simplified expression
      Throws:
      XPathException - if an error is discovered during expression rewriting
    • getExpressionName

      public String getExpressionName()
      Get a name identifying the kind of expression, in terms meaningful to a user.
      Overrides:
      getExpressionName in class Expression
      Returns:
      a name identifying the kind of expression, in terms meaningful to a user. The name will always be in the form of a lexical XML QName, and should match the name used in explain() output displaying the expression.
    • getAtomicComparer

      public AtomicComparer getAtomicComparer()
      Get the AtomicComparer used to compare atomic values. This encapsulates any collation that is used
      Specified by:
      getAtomicComparer in interface ComparisonExpression
    • getSingletonOperator

      public int getSingletonOperator()
      Get the primitive (singleton) operator used: one of Token.FEQ, Token.FNE, Token.FLT, Token.FGT, Token.FLE, Token.FGE
      Specified by:
      getSingletonOperator in interface ComparisonExpression
    • convertsUntypedToOther

      public boolean convertsUntypedToOther()
      Determine whether untyped atomic values should be converted to the type of the other operand
      Specified by:
      convertsUntypedToOther in interface ComparisonExpression
      Returns:
      true if untyped values should be converted to the type of the other operand, false if they should be converted to strings.
    • computeCardinality

      public int computeCardinality()
      Determine the static cardinality. Returns [1..1]
      Overrides:
      computeCardinality in class BinaryExpression
      Returns:
      the computed cardinality, as one of the values StaticProperty.ALLOWS_ZERO_OR_ONE, StaticProperty.EXACTLY_ONE, StaticProperty.ALLOWS_ONE_OR_MORE, StaticProperty.ALLOWS_ZERO_OR_MORE
    • typeCheck

      public Expression typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException
      Type-check the expression
      Overrides:
      typeCheck in class BinaryExpression
      Parameters:
      visitor - an expression visitor
      contextItemType - the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set to Type.ITEM_TYPE
      Returns:
      the checked expression
      Throws:
      XPathException - if an error is discovered during this phase (typically a type error)
    • optimize

      public Expression optimize(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException
      Optimize the expression
      Overrides:
      optimize in class BinaryExpression
      Parameters:
      visitor - an expression visitor
      contextItemType - the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set to Type.ITEM_TYPE
      Returns:
      the checked expression
      Throws:
      XPathException - if an error is discovered during this phase (typically a type error)
    • copy

      public Expression copy()
      Copy an expression. This makes a deep copy.
      Specified by:
      copy in class Expression
      Returns:
      the copy of the original expression
    • evaluateItem

      public Item evaluateItem(XPathContext context) throws XPathException
      Evaluate the expression in a given context
      Overrides:
      evaluateItem in class Expression
      Parameters:
      context - the given context for evaluation
      Returns:
      a BooleanValue representing the result of the numeric comparison of the two operands
      Throws:
      XPathException - if any dynamic error occurs evaluating the expression
    • call

      public SequenceIterator call(SequenceIterator[] arguments, XPathContext context) throws XPathException
      Evaluate the expression
      Specified by:
      call in interface CallableExpression
      Parameters:
      arguments - the values of the arguments, supplied as SequenceIterators
      context - the dynamic evaluation context
      Returns:
      the result of the evaluation, in the form of a SequenceIterator
      Throws:
      XPathException - if a dynamic error occurs during the evaluation of the expression
    • effectiveBooleanValue

      public boolean effectiveBooleanValue(XPathContext context) throws XPathException
      Evaluate the expression in a boolean context
      Overrides:
      effectiveBooleanValue in class Expression
      Parameters:
      context - the given context for evaluation
      Returns:
      a boolean representing the result of the numeric comparison of the two operands
      Throws:
      XPathException - if any dynamic error occurs evaluating the expression
    • evaluateManyToMany

      public boolean evaluateManyToMany(SequenceIterator iter0, SequenceIterator iter1, XPathContext context) throws XPathException
      Evaluate a (zero-or-one)-to-(zero-or-one) comparison
      Parameters:
      iter0 - iterator over the first value
      iter1 - iterator the second value
      context - dynamic evaluation context
      Returns:
      the comparison result
      Throws:
      XPathException - if a dynamic error occurs
    • compare

      public static boolean compare(AtomicValue a0, int operator, AtomicValue a1, AtomicComparer comparer, boolean checkTypes, XPathContext context) throws XPathException
      Compare two atomic values
      Parameters:
      a0 - the first value
      operator - the operator, for example Token.EQUALS
      a1 - the second value
      comparer - the comparer to be used to perform the comparison
      checkTypes - set to true if the operand types need to be checked for comparability at runtime
      context - the XPath evaluation context @return true if the comparison succeeds
      Throws:
      XPathException
    • getItemType

      public ItemType getItemType(TypeHierarchy th)
      Determine the data type of the expression
      Specified by:
      getItemType in class Expression
      Parameters:
      th - the type hierarchy cache
      Returns:
      the value BuiltInAtomicType.BOOLEAN
    • getCorrespondingSingletonOperator

      public static int getCorrespondingSingletonOperator(int op)
      Return the singleton form of the comparison operator, e.g. FEQ for EQUALS, FGT for GT
      Parameters:
      op - the many-to-many form of the operator, for example Token.LE
      Returns:
      the corresponding singleton operator, for example Token.FLE
    • getInverseComparison

      protected GeneralComparison getInverseComparison()
    • explainExtraAttributes

      protected void explainExtraAttributes(ExpressionPresenter out)
      Description copied from class: BinaryExpression
      Add subclass-specific attributes to the expression tree explanation. Default implementation does nothing; this is provided for subclasses to override.
      Overrides:
      explainExtraAttributes in class BinaryExpression
      Parameters:
      out - the output destination for the displayed expression tree