net.sf.saxon.functions
Class Id

java.lang.Object
  |
  +--net.sf.saxon.expr.ComputedExpression
        |
        +--net.sf.saxon.expr.FunctionCall
              |
              +--net.sf.saxon.functions.SystemFunction
                    |
                    +--net.sf.saxon.functions.Id
All Implemented Interfaces:
Container, Expression, InstructionInfoProvider, MappingFunction, java.io.Serializable, javax.xml.transform.SourceLocator

public class Id
extends SystemFunction
implements MappingFunction

The XPath id() function XPath 2.0 version: accepts any sequence as the first parameter; each item in the sequence is taken as an IDREFS value, that is, a space-separated list of ID values. Also accepts an optional second argument to identify the target document, this defaults to the context node.

See Also:
Serialized Form

Field Summary
 
Fields inherited from class net.sf.saxon.functions.SystemFunction
operation
 
Fields inherited from class net.sf.saxon.expr.FunctionCall
argument
 
Fields inherited from class net.sf.saxon.expr.ComputedExpression
locationId, staticProperties
 
Fields inherited from interface net.sf.saxon.expr.Expression
EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD
 
Constructor Summary
Id()
           
 
Method Summary
 void checkArguments(StaticContext env)
          Static analysis: prevent sorting of the argument
 int computeSpecialProperties()
          Get the static properties of this expression (other than its type).
 SequenceIterator iterate(XPathContext context)
          Evaluate the function to return an iteration of selected nodes.
 java.lang.Object map(Item item, XPathContext c, java.lang.Object info)
          Evaluate the function for a single string value (implements the MappingFunction interface)
 Expression preEvaluate(StaticContext env)
          preEvaluate: this method suppresses compile-time evaluation by doing nothing
 Expression simplify(StaticContext env)
          Simplify: add a second implicit argument, the context document
 
Methods inherited from class net.sf.saxon.functions.SystemFunction
addContextDocumentArgument, computeCardinality, display, getDetails, getItemType, getRequiredType, main, makeSystemFunction, setDetails, useContextItemAsDefault
 
Methods inherited from class net.sf.saxon.expr.FunctionCall
analyze, checkArgumentCount, getDisplayName, getFunctionNameCode, getNumberOfArguments, iterateSubExpressions, promote, setArguments, setFunctionNameCode, simplifyArguments
 
Methods inherited from class net.sf.saxon.expr.ComputedExpression
adoptChildExpression, computeDependencies, computeStaticProperties, dynamicError, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, getCardinality, getColumnNumber, getConstructType, getDependencies, getExecutable, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getLineNumber, getLocationId, getParentExpression, getPublicId, getSpecialProperties, getSystemId, markTailFunctionCalls, process, resetStaticProperties, setLocationId, setParentExpression, typeError
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

Id

public Id()
Method Detail

simplify

public Expression simplify(StaticContext env)
                    throws XPathException
Simplify: add a second implicit argument, the context document

Specified by:
simplify in interface Expression
Overrides:
simplify in class FunctionCall
Returns:
the simplified expression
Throws:
XPathException - if an error is discovered during expression rewriting

checkArguments

public void checkArguments(StaticContext env)
                    throws XPathException
Static analysis: prevent sorting of the argument

Overrides:
checkArguments in class SystemFunction
XPathException

preEvaluate

public Expression preEvaluate(StaticContext env)
preEvaluate: this method suppresses compile-time evaluation by doing nothing

Overrides:
preEvaluate in class FunctionCall

computeSpecialProperties

public 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 ComputedExpression

iterate

public SequenceIterator iterate(XPathContext context)
                         throws XPathException
Evaluate the function to return an iteration of selected nodes.

Specified by:
iterate in interface Expression
Overrides:
iterate in class ComputedExpression
Parameters:
context - supplies the context for evaluation
Returns:
a SequenceIterator that can be used to iterate over the result of the expression
Throws:
XPathException - if any dynamic error occurs evaluating the expression

map

public java.lang.Object map(Item item,
                            XPathContext c,
                            java.lang.Object info)
                     throws XPathException
Evaluate the function for a single string value (implements the MappingFunction interface)

Specified by:
map in interface MappingFunction
Parameters:
item - The item to be mapped. If context is supplied, this must be the same as context.currentItem().
c - The processing context. This is supplied only for mapping constructs that set the context node, position, and size. Otherwise it is null.
info - Arbitrary information supplied by the creator of the MappingIterator. It must be read-only and immutable for the duration of the iteration.
Returns:
either (a) a SequenceIterator over the sequence of items that the supplied input item maps to, or (b) an Item if it maps to a single item, or (c) null if it maps to an empty sequence.
XPathException