net.sf.saxon.expr
Class FunctionCall

java.lang.Object
  extended by net.sf.saxon.expr.Expression
      extended by net.sf.saxon.expr.FunctionCall
All Implemented Interfaces:
Serializable, SourceLocator, EvaluableItem, SequenceIterable, InstructionInfoProvider
Direct Known Subclasses:
ExtensionFunctionCall, SystemFunction, UserFunctionCall, XPathFunctionCall

public abstract class FunctionCall
extends Expression

Abstract superclass for calls to system-defined and user-defined functions

See Also:
Serialized Form

Field Summary
 
Fields inherited from class net.sf.saxon.expr.Expression
EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD
 
Constructor Summary
FunctionCall()
           
 
Method Summary
 PathMap.PathMapNodeSet addExternalFunctionCallToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodes)
          Add a representation of this expression to a PathMap.
 boolean equals(Object o)
          Determine whether two expressions are equivalent
 void explain(ExpressionPresenter out)
          Diagnostic print of expression structure.
 Expression[] getArguments()
          Get the expressions supplied as actual arguments to the function
 String getDisplayName()
          Get the name of the function for display in messages
 StructuredQName getFunctionName()
          Get the qualified of the function being called
 int getNumberOfArguments()
          Determine the number of actual arguments supplied in the function call
 int hashCode()
          Get hashCode in support of equals() method
 Iterator iterateSubExpressions()
          Get the immediate subexpressions of this expression
 Expression optimize(ExpressionVisitor visitor, ItemType contextItemType)
          Perform optimisation of an expression and its subexpressions.
 Expression preEvaluate(ExpressionVisitor visitor)
          Pre-evaluate a function at compile time.
 Expression promote(PromotionOffer offer)
          Promote this expression if possible
 boolean replaceSubExpression(Expression original, Expression replacement)
          Replace one subexpression by a replacement subexpression
 void setArguments(Expression[] args)
          Method called by the expression parser when all arguments have been supplied
 void setFunctionName(StructuredQName name)
          Set the name of the function being called
 Expression simplify(ExpressionVisitor visitor)
          Simplify the function call.
 String toString()
          The toString() method for an expression attempts to give a representation of the expression in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath.
 Expression typeCheck(ExpressionVisitor visitor, ItemType contextItemType)
          Type-check the expression.
 
Methods inherited from class net.sf.saxon.expr.Expression
addToPathMap, adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, copy, display, doPromotion, effectiveBooleanValue, evaluateAsString, evaluateItem, explain, findParentOf, getCardinality, getColumnNumber, getContainer, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getItemType, getLineNumber, getLocationId, getLocationProvider, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, iterate, iterateEvents, markTailFunctionCalls, process, setContainer, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation
 
Methods inherited from class java.lang.Object
getClass, notify, notifyAll, wait, wait, wait
 

Constructor Detail

FunctionCall

public FunctionCall()
Method Detail

setFunctionName

public final void setFunctionName(StructuredQName name)
Set the name of the function being called

Parameters:
name - the name of the function

getFunctionName

public StructuredQName getFunctionName()
Get the qualified of the function being called

Returns:
the qualified name

getNumberOfArguments

public final int getNumberOfArguments()
Determine the number of actual arguments supplied in the function call

Returns:
the arity (the number of arguments)

setArguments

public void setArguments(Expression[] args)
Method called by the expression parser when all arguments have been supplied

Parameters:
args - the expressions contained in the argument list of the function call

getArguments

public Expression[] getArguments()
Get the expressions supplied as actual arguments to the function

Returns:
the array of expressions supplied in the argument list of the function call

simplify

public Expression simplify(ExpressionVisitor visitor)
                    throws XPathException
Simplify the function call. Default method is to simplify each of the supplied arguments and evaluate the function if all are now known.

Overrides:
simplify in class Expression
Parameters:
visitor - an expression visitor
Returns:
the simplified expression
Throws:
XPathException - if an error is discovered during expression rewriting

typeCheck

public Expression typeCheck(ExpressionVisitor visitor,
                            ItemType contextItemType)
                     throws XPathException
Type-check the expression. This also calls preEvaluate() to evaluate the function if all the arguments are constant; functions that do not require this behavior can override the preEvaluate method.

Overrides:
typeCheck in class Expression
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 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)

optimize

public Expression optimize(ExpressionVisitor visitor,
                           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 Expression
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

public Expression preEvaluate(ExpressionVisitor visitor)
                       throws XPathException
Pre-evaluate a function at compile time. Functions that do not allow pre-evaluation, or that need access to context information, can override this method.

Parameters:
visitor - an expression visitor
Returns:
the result of the early evaluation, or the original expression, or potentially a simplified expression
Throws:
XPathException

promote

public Expression promote(PromotionOffer offer)
                   throws XPathException
Promote this expression if possible

Overrides:
promote in class Expression
Parameters:
offer - details of the offer, for example the offer to move expressions that don't depend on the context to an outer level in the containing expression
Returns:
if the offer is not accepted, return this expression unchanged. Otherwise return the result of rewriting the expression to promote this subexpression
Throws:
XPathException - if any error is detected

iterateSubExpressions

public Iterator iterateSubExpressions()
Get the immediate subexpressions of this expression

Overrides:
iterateSubExpressions in class Expression
Returns:
an iterator containing the sub-expressions of this expression

replaceSubExpression

public boolean replaceSubExpression(Expression original,
                                    Expression replacement)
Replace one subexpression by a replacement subexpression

Overrides:
replaceSubExpression in class Expression
Parameters:
original - the original subexpression
replacement - the replacement subexpression
Returns:
true if the original subexpression is found

addExternalFunctionCallToPathMap

public PathMap.PathMapNodeSet addExternalFunctionCallToPathMap(PathMap pathMap,
                                                               PathMap.PathMapNodeSet pathMapNodes)
Add a representation of this expression to a PathMap. The PathMap captures a map of the nodes visited by an expression in a source tree.

The default implementation of this method assumes that an expression does no navigation other than the navigation done by evaluating its subexpressions, and that the subexpressions are evaluated in the same context as the containing expression. The method must be overridden for any expression where these assumptions do not hold. For example, implementations exist for AxisExpression, ParentExpression, and RootExpression (because they perform navigation), and for the doc(), document(), and collection() functions because they create a new navigation root. Implementations also exist for PathExpression and FilterExpression because they have subexpressions that are evaluated in a different context from the calling expression.

Parameters:
pathMap - the PathMap to which the expression should be added
pathMapNodes - the node in the PathMap representing the focus at the point where this expression is called. Set to null if this expression appears at the top level, in which case the expression, if it is registered in the path map at all, must create a new path map root.
Returns:
the pathMapNode representing the focus established by this expression, in the case where this expression is the first operand of a path expression or filter expression. For an expression that does navigation, it represents the end of the arc in the path map that describes the navigation route. For other expressions, it is the same as the input pathMapNode.

getDisplayName

public final String getDisplayName()
Get the name of the function for display in messages

Returns:
the name of the function as a lexical QName

toString

public String toString()
The toString() method for an expression attempts to give a representation of the expression in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath. In the case of XSLT instructions, the toString() method gives an abstracted view of the syntax

Overrides:
toString in class Expression

explain

public void explain(ExpressionPresenter out)
Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.

Specified by:
explain in class Expression
Parameters:
out - the expression presenter used to display the structure

equals

public boolean equals(Object o)
Determine whether two expressions are equivalent

Overrides:
equals in class Object

hashCode

public int hashCode()
Get hashCode in support of equals() method

Overrides:
hashCode in class Object


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