Package net.sf.saxon.expr

Class BooleanExpression

java.lang.Object
net.sf.saxon.expr.Expression
net.sf.saxon.expr.BinaryExpression
net.sf.saxon.expr.BooleanExpression
All Implemented Interfaces:
ExportAgent, Locatable, Negatable, IdentityComparable, Traceable
Direct Known Subclasses:
AndExpression, OrExpression
public abstract class BooleanExpression extends BinaryExpression implements Negatable
Boolean expression: two truth values combined using AND or OR.

  • Constructor Details

    • BooleanExpression

      public BooleanExpression(Expression p1, int operator, Expression p2)
      Construct a boolean expression
      Parameters:
      p1 - the first operand
      operator - one of Token.AND or Token.OR
      p2 - the second operand

  • Method Details

    • 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.

    • typeCheck

      public Expression typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) throws XPathException
      Description copied from class: BinaryExpression
      Type-check the expression. Default implementation for binary operators that accept any kind of operand
      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 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)

    • 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.

    • optimize

      public Expression optimize(ExpressionVisitor visitor, ContextItemStaticInfo 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)

    • preEvaluate

      protected abstract Expression preEvaluate()
      Evaluate the expression statically if either or both operands are literals. For example, (true() or X) returns true().
      Returns:
      a boolean literal if the expression can be evaluated now, or the original expression otherwise.

    • forceToBoolean

      protected Expression forceToBoolean(Expression in)

    • isNegatable

      public boolean isNegatable(TypeHierarchy th)
      Check whether this specific instance of the expression is negatable
      Specified by:
      isNegatable in interface Negatable
      Parameters:
      th - the type hierarchy, if needed
      Returns:
      true if it is

    • negate

      public abstract Expression negate()
      Return the negation of this boolean expression, that is, an expression that returns true when this expression returns false, and vice versa
      Specified by:
      negate in interface Negatable
      Returns:
      the negation of this expression

    • evaluateItem

      public BooleanValue evaluateItem(XPathContext context) throws XPathException
      Evaluate the expression
      Overrides:
      evaluateItem in class Expression
      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

    • effectiveBooleanValue

      public abstract boolean effectiveBooleanValue(XPathContext c) throws XPathException
      Evaluate as a boolean.
      Overrides:
      effectiveBooleanValue in class Expression
      Parameters:
      c - The context in which the expression is to be evaluated
      Returns:
      the effective boolean value
      Throws:
      XPathException - if any dynamic error occurs evaluating the expression

    • getItemType

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

    • listAndComponents

      public static void listAndComponents(Expression exp, List<Expression> list)
      Construct a list containing the "anded" subexpressions of an expression: if the expression is (A and B and C), this returns (A, B, C).
      Parameters:
      exp - the expression to be decomposed
      list - the list to which the subexpressions are to be added.

    • getOperandRole

      protected OperandRole getOperandRole(int arg)
      Description copied from class: BinaryExpression
      Get the operand role
      Overrides:
      getOperandRole in class BinaryExpression
      Parameters:
      arg - which argument: 0 for the lhs, 1 for the rhs
      Returns:
      the operand role