Class CastExpression

java.lang.Object
net.sf.saxon.expr.ComputedExpression
net.sf.saxon.expr.UnaryExpression
net.sf.saxon.expr.CastExpression
All Implemented Interfaces:
Serializable, SourceLocator, Container, Expression, InstructionInfoProvider
public final class CastExpression extends UnaryExpression
Cast Expression: implements "cast as data-type ( expression )". It also allows an internal cast, which has the same semantics as a user-requested cast, but maps an empty sequence to an empty sequence.
See Also:

  • Field Details

  • Constructor Details

    • CastExpression

      public CastExpression(Expression source, AtomicType target, boolean allowEmpty)

  • Method Details

    • addAllowedCasts

      static void addAllowedCasts(int source, int[] target)

    • isPossibleCast

      public static boolean isPossibleCast(int source, int target)
      Determine whether casting from a source type to a target type is possible
      Parameters:
      source - a primitive type (one that has an entry in the casting table)
      target - another primitive type
      Returns:
      true if the entry in the casting table is either "Y" (casting always succeeds) or "M" (casting allowed but may fail for some values)

    • simplify

      public Expression simplify(StaticContext env) throws XPathException
      Simplify the expression
      Specified by:
      simplify in interface Expression
      Overrides:
      simplify in class UnaryExpression
      Parameters:
      env - the static context
      Returns:
      the simplified expression
      Throws:
      XPathException - if an error is discovered during expression rewriting

    • typeCheck

      public Expression typeCheck(StaticContext env, ItemType contextItemType) throws XPathException
      Type-check the expression
      Specified by:
      typeCheck in interface Expression
      Overrides:
      typeCheck in class UnaryExpression
      Parameters:
      env - the static context of the expression
      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

    • computeCardinality

      public int computeCardinality()
      Get the static cardinality of the expression
      Overrides:
      computeCardinality in class UnaryExpression

    • getItemType

      public ItemType getItemType(TypeHierarchy th)
      Get the static type of the expression
      Specified by:
      getItemType in interface Expression
      Overrides:
      getItemType in class UnaryExpression
      Parameters:
      th -
      Returns:
      the item type of the items in the result sequence, insofar as this is known statically.

    • computeSpecialProperties

      public int computeSpecialProperties()
      Determine the special properties of this expression
      Overrides:
      computeSpecialProperties in class UnaryExpression
      Returns:
      StaticProperty.NON_CREATIVE.

    • evaluateItem

      public Item evaluateItem(XPathContext context) throws XPathException
      Evaluate the expression
      Specified by:
      evaluateItem in interface Expression
      Overrides:
      evaluateItem in class ComputedExpression
      Parameters:
      context - The context in which the expression is to be evaluated
      Returns:
      the node or atomic value that results from evaluating the expression; or null to indicate that the result is an empty sequence
      Throws:
      XPathException - if any dynamic error occurs evaluating the expression

    • equals

      public boolean equals(Object other)
      Is this expression the same as another expression?
      Overrides:
      equals in class UnaryExpression

    • displayOperator

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

    • castStringToQName

      public static AtomicValue castStringToQName(CharSequence operand, AtomicType targetType, StaticContext env) throws XPathException
      Evaluate the "pseudo-cast" of a string literal to a QName or NOTATION value. This can only happen at compile time
      Returns:
      the QName or NOTATION value that results from casting the string to a QName. This will either be a QNameValue or a DerivedAtomicValue derived from QName or NOTATION
      Throws:
      XPathException