com.saxonica.functions.hof

Class DynamicFunctionCallDefinition.DynamicFunctionCall

java.lang.Object

net.sf.saxon.lib.ExtensionFunctionCall

com.saxonica.functions.hof.DynamicFunctionCallDefinition.DynamicFunctionCall

All Implemented Interfaces:

Callable

Enclosing class:

DynamicFunctionCallDefinition

public static class DynamicFunctionCallDefinition.DynamicFunctionCall
extends ExtensionFunctionCall

Constructor Summary

Constructors

Constructor and Description
DynamicFunctionCallDefinition.DynamicFunctionCall()

Method Summary

Methods

Modifier and Type	Method and Description
Sequence	call(XPathContext context, Sequence[] arguments) Evaluate this function call at run-time
Expression	rewrite(StaticContext context, Expression[] arguments) Rewrite the function call.

Methods inherited from class net.sf.saxon.lib.ExtensionFunctionCall

copyLocalData, effectiveBooleanValue, getContainer, getDefinition, getStreamingImplementation, setDefinition, supplyStaticContext

Methods inherited from class java.lang.Object

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

Constructor Detail

DynamicFunctionCallDefinition.DynamicFunctionCall

public DynamicFunctionCallDefinition.DynamicFunctionCall()

Method Detail

rewrite

public Expression rewrite(StaticContext context,
                 Expression[] arguments)
                   throws XPathException

Rewrite the function call. This method is called at compile time. It gives the implementation an opportunity to replace itself with an optimized implementation that returns the same result.

There is also an opportunity to perform static checking at this stage and to throw an error if the arguments are invalid.

Overrides:

rewrite in class ExtensionFunctionCall

Parameters:

context - The static context in which the function call appears. The method must not modify the static context.

arguments - The XPath expressions supplied in the call to this function. This method is called after type-checking, so these expressions may have been modified by adding atomization operators or type-checking operations, for example.

Returns:

an expression to be evaluated at run-time in place of this function call. Return null if no rewriting is required and the function call should be used unchanged. Return a Literal representing the result of the function call if the function call can be precomputed at compile time

Throws:

XPathException - if the implementation is able to detect a static error in the way the function is being called (for example it might require that the types of the arguments are consistent with each other).

call

public Sequence call(XPathContext context,
            Sequence[] arguments)
              throws XPathException

Evaluate this function call at run-time

Specified by:

call in interface Callable

Specified by:

call in class ExtensionFunctionCall

Parameters:

context - The XPath dynamic evaluation context

arguments - The values of the arguments to the function call. Each argument value (which is in general a sequence) is supplied in the form of Sequence. Any required conversions to the declared types of the arguments will already have been performed.

If the argument is always a singleton, then the single item may be obtained by calling arguments[i].head().

The implementation is not obliged to read all the items in each SequenceIterator if they are not required to compute the result; but if any SequenceIterator is not read to completion, it is good practice to call its close() method.

Returns:

the results of the function as a Sequence.

The implementation is responsible for ensuring that the result is a valid instance of the declared result type. Saxon will check that this is the case if the ExtensionFunctionDefinition.trustResultType() method returns false, but it will never convert the supplied result value to the declared result type.

The Sequence objects used for the arguments will often be instances of LazySequence, which means that the items in the sequence are computed lazily on demand. This means that any errors that occur while computing the sequence might not be thrown until the relevant item is actually read from the sequence.

If the result is a single item, it can be returned directly, since single items all implement Sequence. For example a string can be returned as an instance of StringValue, and a boolean as an instance of BooleanValue. If the result is an empty sequence, the method should return EmptySequence.getInstance()

Throws:

XPathException - if a dynamic error occurs during evaluation of the function. The Saxon run-time code will add information about the error location.