## 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:
  Serializable, SourceLocator, Container, EvaluableItem, SequenceIterable, InstructionInfoProvider

    public class BooleanExpression

extends BinaryExpression

Boolean expression: two truth values combined using AND or OR.

See Also:
  Serialized Form

Field Summary

Fields inherited from class net.sf.saxon.expr.Expression
`EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD`

Constructor Summary
`BooleanExpression(Expression p1, int operator, Expression p2)`

Method Summary
`int` `computeCardinality()` Determine the static cardinality.
`boolean` `effectiveBooleanValue(XPathContext c)` Evaluate as a boolean.
`Item` `evaluateItem(XPathContext context)` Evaluate the expression
`ItemType` `getItemType(TypeHierarchy th)` Determine the data type of the expression
`static void` `listAndComponents(Expression exp, List 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).
`Expression` `negate(StaticContext env)` Return the negation of this boolean expression, that is, an expression that returns true when this expression returns false, and vice versa
`Expression` `optimize(Optimizer opt, StaticContext env, ItemType contextItemType)` Perform optimisation of an expression and its subexpressions.
`Expression` `typeCheck(StaticContext env, ItemType contextItemType)` Type-check the expression.

Methods inherited from class net.sf.saxon.expr.BinaryExpression
`computeSpecialProperties, display, equals, getOperands, getOperator, hashCode, iterateSubExpressions, promote, replaceSubExpression, simplify`

Methods inherited from class net.sf.saxon.expr.Expression

`adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, evaluateAsString, getCardinality, getColumnNumber, getContainingProcedure, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getLineNumber, getLocationId, getLocationProvider, getParentExpression, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasBadParentPointer, iterate, markTailFunctionCalls, process, resetStaticProperties, setLocationId, setParentExpression, setParentExpression, suppressValidation`

Methods inherited from class java.lang.Object
`getClass, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### BooleanExpression

    public BooleanExpression(Expression p1,
                             int operator,
                             Expression p2)

Method Detail

### typeCheck

    public Expression typeCheck(StaticContext env,
                                ItemType contextItemType)
                         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:
    `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:
    `StaticError` - if an error is discovered during this phase (typically a type error)
    `XPathException`

### computeCardinality

    public int computeCardinality()

  Determine the static cardinality. Returns [1..1]

  Overrides:
    `computeCardinality` in class `BinaryExpression`

### optimize

    public Expression optimize(Optimizer opt,
                               StaticContext env,
                               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:
    `opt` - the optimizer in use. This provides access to supporting functions; it also allows different optimization strategies to be used in different circumstances.
    `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 if appropriate to optimize execution
  Throws:
    `StaticError` - if an error is discovered during this phase (typically a type error)
    `XPathException`

### negate

    public Expression negate(StaticContext env)

  Return the negation of this boolean expression, that is, an expression that returns true when this expression returns false, and vice versa

### evaluateItem

    public Item evaluateItem(XPathContext context)
                      throws XPathException

  Evaluate the expression

  Specified by:
    `evaluateItem` in interface `EvaluableItem`
  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 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(TypeHierarchy th)

  Determine the data type of the expression

  Specified by:
    `getItemType` in class `Expression`
  Parameters:
    `th` -
  Returns:
    Type.BOOLEAN

### listAndComponents

    public static void listAndComponents(Expression exp,
                                         List 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.

Copyright (C) Michael H. Kay. All rights reserved.