net.sf.saxon.expr

Class FunctionCall

public abstract class FunctionCall extends Expression

Abstract superclass for calls to system-defined and user-defined functions
Field Summary
protected Expression[]argument
The array of expressions representing the actual parameters to the function call
Method Summary
PathMap.PathMapNodeSetaddExternalFunctionCallToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodes)
Add a representation of this expression to a PathMap.
protected intcheckArgumentCount(int min, int max, ExpressionVisitor visitor)
Check number of arguments.
protected abstract voidcheckArguments(ExpressionVisitor visitor)
Method supplied by each class of function to check arguments during parsing, when all the argument expressions have been read
booleanequals(Object o)
Determine whether two expressions are equivalent
voidexplain(ExpressionPresenter out)
Diagnostic print of expression structure.
Expression[]getArguments()
Get the expressions supplied as actual arguments to the function
StringgetDisplayName()
Get the name of the function for display in messages
StructuredQNamegetFunctionName()
Get the qualified of the function being called
intgetNumberOfArguments()
Determine the number of actual arguments supplied in the function call
inthashCode()
Get hashCode in support of equals() method
Iterator<Expression>iterateSubExpressions()
Get the immediate subexpressions of this expression
Expressionoptimize(ExpressionVisitor visitor, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.
ExpressionpreEvaluate(ExpressionVisitor visitor)
Pre-evaluate a function at compile time.
Expressionpromote(PromotionOffer offer, Expression parent)
Promote this expression if possible
booleanreplaceSubExpression(Expression original, Expression replacement)
Replace one subexpression by a replacement subexpression
voidsetArguments(Expression[] args)
Method called by the expression parser when all arguments have been supplied
voidsetFunctionName(StructuredQName name)
Set the name of the function being called
Expressionsimplify(ExpressionVisitor visitor)
Simplify the function call.
protected ExpressionsimplifyArguments(ExpressionVisitor visitor)
Simplify the arguments of the function.
StringtoString()
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.
ExpressiontypeCheck(ExpressionVisitor visitor, ItemType contextItemType)
Type-check the expression.

Field Detail

argument

protected Expression[] argument
The array of expressions representing the actual parameters to the function call

Method Detail

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.

checkArgumentCount

protected int checkArgumentCount(int min, int max, ExpressionVisitor visitor)
Check number of arguments.
A convenience routine for use in subclasses.

Parameters: min the minimum number of arguments allowed max the maximum number of arguments allowed visitor an expression visitor

Returns: the actual number of arguments

Throws: net.sf.saxon.trans.XPathException if the number of arguments is out of range

checkArguments

protected abstract void checkArguments(ExpressionVisitor visitor)
Method supplied by each class of function to check arguments during parsing, when all the argument expressions have been read

Parameters: visitor the expression visitor

equals

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

explain

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

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

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

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)

hashCode

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

iterateSubExpressions

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

optimize

public Expression optimize(ExpressionVisitor visitor, ItemType contextItemType)
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.

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 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)
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

promote

public Expression promote(PromotionOffer offer, Expression parent)
Promote this expression if possible

replaceSubExpression

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

Parameters: original the original subexpression replacement the replacement subexpression

Returns: true if the original subexpression is found

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

setFunctionName

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

Parameters: name the name of the function

simplify

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

Parameters: visitor an expression visitor

simplifyArguments

protected final Expression simplifyArguments(ExpressionVisitor visitor)
Simplify the arguments of the function. Called from the simplify() method of each function.

Parameters: visitor an expression visitor

Returns: the result of simplifying the arguments of the expression

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

typeCheck

public Expression typeCheck(ExpressionVisitor visitor, ItemType contextItemType)
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.