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: Class SingletonExpression

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com.icl.saxon.expr
Class SingletonExpression


java.lang.Object

  |

  +--com.icl.saxon.expr.Expression

        |

        +--com.icl.saxon.expr.NodeSetExpression

              |

              +--com.icl.saxon.expr.SingletonExpression

Direct Known Subclasses:: ContextNodeExpression, ParentNodeExpression, RootExpression

public abstract class SingletonExpression
extends NodeSetExpression

A node set expression that will always return zero or one nodes

Fields inherited from class com.icl.saxon.expr.Expression

staticContext

Constructor Summary

SingletonExpression()


Method Summary

NodeEnumeration enumerate(Context context, boolean sort)
          Evaluate the expression in a given context to return a Node enumeration

boolean evaluateAsBoolean(Context context)
          Evaluate as a boolean.

NodeSetValue evaluateAsNodeSet(Context context)
          Evaluate an expression as a NodeSet.

java.lang.String evaluateAsString(Context context)
          Evaluate as a string.

abstract NodeInfo getNode(Context context)
          Get the single node to which this expression refers

boolean isContextDocumentNodeSet()
          Determine, in the case of an expression whose data type is Value.NODESET, whether all the nodes in the node-set are guaranteed to come from the same document as the context node.

NodeInfo selectFirst(Context context)
          Return the first node selected by this Expression when evaluated in the current context

Methods inherited from class com.icl.saxon.expr.NodeSetExpression

evaluate, getDataType, outputStringValue

Methods inherited from class com.icl.saxon.expr.Expression

containsReferences, display, evaluateAsNumber, getDependencies, getStaticContext, indent, make, reduce, setStaticContext, simplify, usesCurrent

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

SingletonExpression


public SingletonExpression()

Method Detail

isContextDocumentNodeSet


public boolean isContextDocumentNodeSet()

Determine, in the case of an expression whose data type is Value.NODESET, whether all the nodes in the node-set are guaranteed to come from the same document as the context node. Used for optimization.

Overrides:: isContextDocumentNodeSet in class Expression

getNode


public abstract NodeInfo getNode(Context context)
                          throws XPathException

Get the single node to which this expression refers

selectFirst


public NodeInfo selectFirst(Context context)
                     throws XPathException

Return the first node selected by this Expression when evaluated in the current context

Overrides:: selectFirst in class NodeSetExpression

Parameters:: context - The context for the evaluation
Returns:: the NodeInfo of the first node in document order, or null if the node-set is empty.

enumerate


public NodeEnumeration enumerate(Context context,
                                 boolean sort)
                          throws XPathException

Evaluate the expression in a given context to return a Node enumeration

Overrides:: enumerate in class NodeSetExpression

Parameters:: context - the evaluation context; sort - Indicates result must be in document order

evaluateAsNodeSet


public NodeSetValue evaluateAsNodeSet(Context context)
                               throws XPathException

Evaluate an expression as a NodeSet.

Overrides:: evaluateAsNodeSet in class NodeSetExpression

Parameters:: context - The context in which the expression is to be evaluated
Returns:: the value of the expression, evaluated in the current context

evaluateAsString


public java.lang.String evaluateAsString(Context context)
                                  throws XPathException

Evaluate as a string. Returns the string value of the node if it exists

Overrides:: evaluateAsString in class NodeSetExpression

Parameters:: context - The context in which the expression is to be evaluated
Returns:: true if there are any nodes selected by the NodeSetExpression

evaluateAsBoolean


public boolean evaluateAsBoolean(Context context)
                          throws XPathException

Evaluate as a boolean. Returns true if there are any nodes selected by the NodeSetExpression

Overrides:: evaluateAsBoolean in class NodeSetExpression

Parameters:: context - The context in which the expression is to be evaluated
Returns:: true if there are any nodes selected by the NodeSetExpression