Package net.sf.saxon.expr

Class UnaryExpression

java.lang.Object
net.sf.saxon.expr.Expression
net.sf.saxon.expr.UnaryExpression
All Implemented Interfaces:
ExportAgent, Locatable, IdentityComparable, Traceable
Direct Known Subclasses:
AdjacentTextNodeMerger, AtomicSequenceConverter, Atomizer, CardinalityChecker, CastingExpression, CompareToConstant, ConsumingOperand, DocumentSorter, EmptyTextNodeRemover, FunctionSequenceCoercer, HomogeneityChecker, InstanceOfExpression, ItemChecker, LookupAllExpression, NegateExpression, OnEmptyExpr, OnNonEmptyExpr, SequenceInstr, SingleItemFilter, SingletonAtomizer, TailCallLoop, TailExpression, WherePopulated
public abstract class UnaryExpression extends Expression
Unary Expression: an expression taking a single operand expression

  • Constructor Details

    • UnaryExpression

      public UnaryExpression(Expression p0)

  • Method Details

    • getBaseExpression

      public Expression getBaseExpression()

    • setBaseExpression

      public void setBaseExpression(Expression child)

    • getOperand

      public Operand getOperand()

    • operands

      public Iterable<Operand> operands()
      Description copied from class: Expression
      Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression.

      If the expression is a Callable, then it is required that the order of the operands returned by this function is the same as the order of arguments supplied to the corresponding call() method.

      Overrides:
      operands in class Expression
      Returns:
      an iterator containing the sub-expressions of this expression

    • getOperandRole

      protected abstract OperandRole getOperandRole()
      Get the usage (in terms of streamability analysis) of the single operand
      Returns:
      the operand usage

    • typeCheck

      public Expression typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) throws XPathException
      Type-check the expression. Default implementation for unary operators that accept any kind of operand
      Overrides:
      typeCheck in class Expression
      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 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, ContextItemStaticInfo contextInfo) 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 Expression
      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 original expression, rewritten if appropriate to optimize execution
      Throws:
      XPathException - if an error is discovered during this phase (typically a type error)

    • computeSpecialProperties

      protected int computeSpecialProperties()
      Get the static properties of this expression (other than its type). The result is bit-signficant. These properties are used for optimizations. In general, if property bit is set, it is true, but if it is unset, the value is unknown.
      Overrides:
      computeSpecialProperties in class Expression
      Returns:
      the special properties, as a bit-significant integer

    • computeCardinality

      protected int computeCardinality()
      Determine the static cardinality. Default implementation returns the cardinality of the operand
      Specified by:
      computeCardinality in class Expression
      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.

    • getItemType

      public ItemType getItemType()
      Determine the data type of the expression, if possible. The default implementation for unary expressions returns the item type of the operand
      Specified by:
      getItemType in class Expression
      Returns:
      the item type of the items in the result sequence, insofar as this is known statically.

    • equals

      public boolean equals(Object other)
      Is this expression the same as another expression?
      Overrides:
      equals in class Expression
      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 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 Expression
      Returns:
      a computed hash code

    • toString

      public String toString()
      The toString() method for an expression attempts to give a representation of the expression in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath. In the case of XSLT instructions, the toString() method gives an abstracted view of the syntax
      Overrides:
      toString in class Expression
      Returns:
      a representation of the expression as a string

    • toShortString

      public String toShortString()
      Description copied from class: Expression
      Produce a short string identifying the expression for use in error messages
      Overrides:
      toShortString in class Expression
      Returns:
      a short string, sufficient to identify the expression

    • export

      public void export(ExpressionPresenter out) throws XPathException
      Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.
      Specified by:
      export in interface ExportAgent
      Specified by:
      export in class Expression
      Parameters:
      out - the expression presenter used to display the structure
      Throws:
      XPathException - if the export fails, for example if an expression is found that won't work in the target environment.

    • emitExtraAttributes

      protected void emitExtraAttributes(ExpressionPresenter out)

    • displayOperator

      protected String displayOperator(Configuration config)
      Give a string representation of the operator for use in diagnostics
      Parameters:
      config - the Saxon configuration
      Returns:
      the operator, as a string