net.sf.saxon.functions

Class SystemFunction

public abstract class SystemFunction extends FunctionCall

Abstract superclass for system-defined and user-defined functions
Field Summary
protected intoperation
Method Summary
protected voidaddContextDocumentArgument(int pos, String augmentedName)
Add an implicit argument referring to the context document.
PathMap.PathMapNodeSetaddDocToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodes)
Add a representation of a doc() call or similar function to a PathMap.
voidcheckArguments(ExpressionVisitor visitor)
Method called during static type checking
intcomputeCardinality()
Determine the cardinality of the function.
intcomputeSpecialProperties()
Determine the special properties of this expression.
Expressioncopy()
Copy an expression.
StandardFunction.EntrygetDetails()
Get the details of the function signature
StringgetErrorCodeForTypeErrors()
Return the error code to be used for type errors.
ItemTypegetItemType(TypeHierarchy th)
Determine the item type of the value returned by the function
protected SequenceTypegetRequiredType(int arg)
Get the required type of the nth argument
static FunctionCallmakeSystemFunction(String name, Expression[] arguments)
Make a system function call (one in the standard function namespace).
Expressionoptimize(ExpressionVisitor visitor, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.
voidsetDetails(StandardFunction.Entry entry)
Set the details of this type of function
protected voiduseContextItemAsDefault()
Set "." as the default value for the first and only argument.

Field Detail

operation

protected int operation

Method Detail

addContextDocumentArgument

protected final void addContextDocumentArgument(int pos, String augmentedName)
Add an implicit argument referring to the context document. Called by functions such as id() and key() that take the context document as an implicit argument

Parameters: pos the position of the argument whose default value is ".", zero-based augmentedName the name to be used for the function call with its extra argument. There are some cases where user function calls cannot supply the argument directly (notably unparsed-entity-uri() and unparsed-entity-public-id()) and in these cases a synthesized function name is used for the new function call.

addDocToPathMap

public PathMap.PathMapNodeSet addDocToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodes)
Add a representation of a doc() call or similar function to a PathMap. This is a convenience method called by the addToPathMap() methods for doc(), document(), collection() and similar functions. These all create a new root expression in the path map.

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.

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

checkArguments

public void checkArguments(ExpressionVisitor visitor)
Method called during static type checking

computeCardinality

public int computeCardinality()
Determine the cardinality of the function.

computeSpecialProperties

public int computeSpecialProperties()
Determine the special properties of this expression. The general rule is that a system function call is non-creative if its return type is atomic, or if all its arguments are non-creative. This is overridden for the generate-id() function, which is considered creative if its operand is creative (because the result depends on the identity of the operand)

copy

public Expression copy()
Copy an expression. This makes a deep copy.

Returns: the copy of the original expression

getDetails

public StandardFunction.Entry getDetails()
Get the details of the function signature

Returns: information about the function signature

getErrorCodeForTypeErrors

public String getErrorCodeForTypeErrors()
Return the error code to be used for type errors. This is overridden for functions such as exactly-one(), one-or-more(), ...

Returns: the error code to be used for type errors in the function call. Normally XPTY0004, but different codes are used for functions such as exactly-one()

getItemType

public ItemType getItemType(TypeHierarchy th)
Determine the item type of the value returned by the function

Parameters: th the type hierarchy cache

getRequiredType

protected SequenceType getRequiredType(int arg)
Get the required type of the nth argument

Parameters: arg the number of the argument whose type is requested, zero-based

Returns: the required type of the argument as defined in the function signature

makeSystemFunction

public static FunctionCall makeSystemFunction(String name, Expression[] arguments)
Make a system function call (one in the standard function namespace).

Parameters: name The local name of the function. arguments the arguments to the function call

Returns: a FunctionCall that implements this function, if it exists, or null if the function is unknown.

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)

setDetails

public void setDetails(StandardFunction.Entry entry)
Set the details of this type of function

Parameters: entry information giving details of the function signature

useContextItemAsDefault

protected final void useContextItemAsDefault()
Set "." as the default value for the first and only argument. Called from subclasses.