Package net.sf.saxon.expr

Class GeneralComparison

java.lang.Object
net.sf.saxon.expr.Expression
net.sf.saxon.expr.BinaryExpression
net.sf.saxon.expr.GeneralComparison
All Implemented Interfaces:
ComparisonExpression, ExportAgent, Locatable, IdentityComparable, Traceable
Direct Known Subclasses:
GeneralComparison20, GeneralEqualityEE
public abstract class GeneralComparison extends BinaryExpression implements ComparisonExpression
GeneralComparison: a boolean expression that compares two expressions for equals, not-equals, greater-than or less-than. This implements the operators =, !=, <, >, etc. This implementation is not used when in backwards-compatible mode

  • Field Details

    • singletonOperator

      protected int singletonOperator

    • comparer

      protected AtomicComparer comparer

    • runtimeCheckNeeded

      protected boolean runtimeCheckNeeded

    • comparisonCardinality

      protected GeneralComparison.ComparisonCardinality comparisonCardinality

    • doneWarnings

      protected boolean doneWarnings

  • 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
      Returns:
      true if the types of the operands need to be checked at run-time

    • setNeedsRuntimeCheck

      public void setNeedsRuntimeCheck(boolean needsCheck)
      Say whether a runtime check of the types of the operands is needed
      Parameters:
      needsCheck - true if the types of the operands need to be checked at run-time

    • getComparisonCardinality

      public GeneralComparison.ComparisonCardinality 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).
      Returns:
      the Cardinality of the comparison as one of the values GeneralComparison.ComparisonCardinality.ONE_TO_ONE, GeneralComparison.ComparisonCardinality.MANY_TO_MANY, GeneralComparison.ComparisonCardinality.MANY_TO_ONE

    • setComparisonCardinality

      public void setComparisonCardinality(GeneralComparison.ComparisonCardinality card)
      Say whether the comparison is known to be many-to-one, one-to-one, or many-to-many.
      Parameters:
      card - the Cardinality of the comparison as one of the values GeneralComparison.ComparisonCardinality.ONE_TO_ONE, GeneralComparison.ComparisonCardinality.MANY_TO_MANY, GeneralComparison.ComparisonCardinality.MANY_TO_ONE

    • setAtomicComparer

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

    • 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.

    • getNamespaceResolver

      public NamespaceResolver getNamespaceResolver()
      Get the namespace context for this expression, needed in the event that one operand contains untyped atomic values and the other contains QNames
      Returns:
      the resolver used for namespace prefix resolution

    • 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
      Returns:
      the comparer

    • getStringCollator

      public StringCollator getStringCollator()
      Get the StringCollator used to compare string values.
      Specified by:
      getStringCollator in interface ComparisonExpression
      Returns:
      the collator. May return null if the expression will never be used to compare strings

    • 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
      Returns:
      the operator, as defined in class Token

    • 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

      protected 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. May also return StaticProperty.ALLOWS_ZERO if the result is known to be an empty sequence, or StaticProperty.ALLOWS_MANY if if is known to return a sequence of length two or more.

    • typeCheck

      public Expression typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) throws XPathException
      Type-check the expression
      Overrides:
      typeCheck in class BinaryExpression
      Parameters:
      visitor - an expression visitor
      contextInfo - Information available statically about the context item: whether it is (possibly) absent; its static type; its streaming posture.
      Returns:
      the checked expression
      Throws:
      XPathException - if an error is discovered during this phase (typically a type error)

    • getIntrinsicDependencies

      public int getIntrinsicDependencies()
      Description copied from class: Expression
      Determine the intrinsic dependencies of an expression, that is, those which are not derived from the dependencies of its subexpressions. For example, position() has an intrinsic dependency on the context position, while (position()+1) does not. The default implementation of the method returns 0, indicating "no dependencies".
      Overrides:
      getIntrinsicDependencies in class Expression
      Returns:
      an integer containing bit-significant flags identifying the "intrinsic" dependencies. The flags are documented in class net.sf.saxon.value.StaticProperty

    • equals

      public boolean equals(Object other)
      Description copied from class: BinaryExpression
      Is this expression the same as another expression?
      Overrides:
      equals in class BinaryExpression
      Parameters:
      other - the other operand; the result is false if this is not an Expression
      Returns:
      true if the other operand is an expression and if it can be determined that the two expressions are equivalent, in the sense that they will always return the same result.

    • computeHashCode

      protected int computeHashCode()
      Get a hashCode for comparing two expressions. Note that this hashcode gives the same result for (A op B) and for (B op A), whether or not the operator is commutative.
      Overrides:
      computeHashCode in class BinaryExpression
      Returns:
      a computed hash code

    • optimize

      public Expression optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) throws XPathException
      Optimize the expression
      Overrides:
      optimize in class BinaryExpression
      Parameters:
      visitor - an expression visitor
      contextInfo - 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)

    • evaluateItem

      public BooleanValue 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

    • 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

    • compare

      public static boolean compare(AtomicValue a0, int operator, AtomicValue a1, AtomicComparer comparer, boolean checkTypes, XPathContext context, NamespaceResolver nsResolver) throws XPathException
      Compare two atomic values
      Parameters:
      a0 - the first value
      operator - the singleton version of the comparison operator, for example Token.FEQ
      a1 - the second value
      comparer - the comparer to be used to perform the comparison. If the comparer is context-sensitive then the context must already have been bound using comparer.provideContext().
      checkTypes - set to true if the operand types need to be checked for comparability at runtime
      context - the XPath evaluation context
      nsResolver - namespace resolver
      Returns:
      true if the comparison succeeds
      Throws:
      XPathException - if a dynamic error occurs during the comparison

    • getItemType

      public ItemType getItemType()
      Determine the data type of the expression
      Specified by:
      getItemType in class Expression
      Returns:
      the value BuiltInAtomicType.BOOLEAN

    • getStaticUType

      public UType getStaticUType(UType contextItemType)
      Get the static type of the expression as a UType, following precisely the type inference rules defined in the XSLT 3.0 specification.
      Overrides:
      getStaticUType in class Expression
      Parameters:
      contextItemType - static information about the context item
      Returns:
      the static item type of the expression according to the XSLT 3.0 defined rules

    • 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()

    • getStreamerName

      public String getStreamerName()
      Get the (partial) name of a class that supports streaming of this kind of expression
      Overrides:
      getStreamerName in class Expression
      Returns:
      the partial name of a class that can be instantiated to provide streaming support in Saxon-EE, or null if there is no such class

    • tag

      protected String tag()
      Get the element name used to identify this expression in exported expression format
      Overrides:
      tag in class BinaryExpression
      Returns:
      the element name used to identify this expression

    • 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

    • getElaborator

      public Elaborator getElaborator()
      Make an elaborator for this expression
      Overrides:
      getElaborator in class Expression
      Returns:
      a suitable elaborator