Package net.sf.saxon.expr

Class ValueComparison

java.lang.Object
net.sf.saxon.expr.Expression
net.sf.saxon.expr.BinaryExpression
net.sf.saxon.expr.ValueComparison
All Implemented Interfaces:
Serializable, SourceLocator, LocationProvider, SaxonLocator, ComparisonExpression, EvaluableItem, Negatable, SequenceIterable, InstructionInfo, Locator
public final class ValueComparison extends BinaryExpression implements ComparisonExpression, Negatable
ValueComparison: a boolean expression that compares two atomic values for equals, not-equals, greater-than or less-than. Implements the operators eq, ne, lt, le, gt, ge
See Also:

  • Constructor Details

    • ValueComparison

      public ValueComparison(Expression p1, int op, Expression p2)
      Create a relational expression identifying the two operands and the operator
      Parameters:
      p1 - the left-hand operand
      op - the operator, as a token returned by the Tokenizer (e.g. Token.LT)
      p2 - the right-hand operand

  • Method Details

    • setAtomicComparer

      public void setAtomicComparer(AtomicComparer comparer)
      Set the AtomicComparer used to compare atomic values
      Parameters:
      comparer - the AtomicComparer

    • getAtomicComparer

      public AtomicComparer getAtomicComparer()
      Get the AtomicComparer used to compare atomic values. This encapsulates any collation that is used. Note that the comparer is always known at compile time.
      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.

    • setResultWhenEmpty

      public void setResultWhenEmpty(BooleanValue value)
      Set the result to be returned if one of the operands is an empty sequence
      Parameters:
      value - the result to be returned if an operand is empty. Supply null to mean the empty sequence.

    • getResultWhenEmpty

      public BooleanValue getResultWhenEmpty()
      Get the result to be returned if one of the operands is an empty sequence
      Returns:
      BooleanValue.TRUE, BooleanValue.FALSE, or null (meaning the empty sequence)

    • needsRuntimeComparabilityCheck

      public boolean needsRuntimeComparabilityCheck()
      Determine whether a run-time check is needed to check that the types of the arguments are comparable
      Returns:
      true if a run-time check is needed

    • typeCheck

      public Expression typeCheck(ExpressionVisitor visitor, ItemType 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 original expression, rewritten to perform necessary run-time type checks, and to perform other type-related optimizations
      Throws:
      XPathException - if an error is discovered during this phase (typically a type error)

    • optimize

      public Expression optimize(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException
      Perform optimisation of an expression and its subexpressions.

      This method is called after all references to functions and variables have been resolved to the declaration of the function or variable, and after all type checking has been done.

      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 original expression, rewritten if appropriate to optimize execution
      Throws:
      XPathException - if an error is discovered during this phase (typically a type error)

    • isNegatable

      public boolean isNegatable(ExpressionVisitor visitor)
      Check whether this specific instance of the expression is negatable
      Specified by:
      isNegatable in interface Negatable
      Returns:
      true if it is

    • negate

      public Expression negate()
      Return the negation of this value comparison: that is, a value comparison that returns true() if and only if the original returns false(). The result must be the same as not(this) even in the case where one of the operands is ().
      Specified by:
      negate in interface Negatable
      Returns:
      the inverted comparison

    • 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

    • effectiveBooleanValue

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

    • evaluateItem

      public Item evaluateItem(XPathContext context) throws XPathException
      Evaluate the expression in a given context
      Specified by:
      evaluateItem in interface EvaluableItem
      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, or null representing the empty sequence
      Throws:
      XPathException - if any dynamic error occurs evaluating the expression

    • 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:
      Type.BOOLEAN

    • computeCardinality

      public int computeCardinality()
      Determine the static cardinality.
      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

    • displayOperator

      protected String displayOperator()
      Overrides:
      displayOperator in class BinaryExpression