Package net.sf.saxon.expr

Class FunctionCall

java.lang.Object
net.sf.saxon.expr.Expression
net.sf.saxon.expr.FunctionCall
All Implemented Interfaces:
ExportAgent, Locatable, IdentityComparable, Traceable
Direct Known Subclasses:
IntegratedFunctionCall, JavaExtensionFunctionCall, JavaExtensionLibrary.UnresolvedExtensionFunctionCall, StaticFunctionCall, UserFunctionCall, XPathFunctionCall
public abstract class FunctionCall extends Expression
Abstract superclass for calls to system-defined and user-defined functions

  • Constructor Details

    • FunctionCall

      public FunctionCall()

  • Method Details

    • setOperanda

      protected void setOperanda(OperandArray operanda)
      Set the data structure for the operands of this expression. This must be created during initialisation of the expression and must not be subsequently changed
      Parameters:
      operanda - the data structure for expression operands

    • getOperanda

      public OperandArray getOperanda()
      Get the data structure holding the operands of this expression.
      Returns:
      the data structure holding expression operands

    • operands

      public Iterable<Operand> operands()
      Description copied from class: Expression
      Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression.

      If the expression is a Callable, then it is required that the order of the operands returned by this function is the same as the order of arguments supplied to the corresponding call() method.

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

    • getTargetFunction

      public abstract FunctionItem getTargetFunction(XPathContext context) throws XPathException
      Get the target function to be called
      Parameters:
      context - the dynamic evaluation context
      Returns:
      the target function
      Throws:
      XPathException - if the target function cannot be determined

    • getFunctionName

      public abstract StructuredQName getFunctionName()
      Get the qualified of the function being called
      Returns:
      the qualified name. May be null if the function is anonymous.

    • getArity

      public final int getArity()
      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

    • setOperanda

      protected void setOperanda(Expression[] args, OperandRole[] roles)

    • 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. The array is newly constructed to ensure that modifications to the array have no effect.

    • getArg

      public Expression getArg(int n)
      Get the expression supplied as the Nth argument
      Parameters:
      n - the required argument, zero-based
      Returns:
      the expression supplied in the relevant position
      Throws:
      IllegalArgumentException - if the value of n is out of range

    • setArg

      public void setArg(int n, Expression child)
      Set the expression to be used as the Nth argument
      Parameters:
      n - the required argument, zero-based
      child - the expression to be used in the relevant position
      Throws:
      IllegalArgumentException - if the value of n is out of range

    • simplifyArguments

      protected final Expression simplifyArguments(StaticContext env) throws XPathException
      Simplify the arguments of the function. Called from the simplify() method of each function.
      Parameters:
      env - the static context
      Returns:
      the result of simplifying the arguments of the expression
      Throws:
      XPathException - if an error occurs

    • typeCheck

      public Expression typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) 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
      contextInfo - Information available statically about the context item: whether it is (possibly) absent; its static type; its streaming posture.
      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)

    • preEvaluateIfConstant

      protected Expression preEvaluateIfConstant(ExpressionVisitor visitor) throws XPathException
      Throws:
      XPathException

    • checkFunctionCall

      public void checkFunctionCall(FunctionItem target, ExpressionVisitor visitor) throws XPathException
      Check the function call against the declared function signature, applying the function conversion rules to each argument as necessary
      Parameters:
      target - the function being called
      visitor - an expression visitor
      Throws:
      XPathException - if there is a type error

    • optimize

      public Expression optimize(ExpressionVisitor visitor, ContextItemStaticInfo 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)

    • getNetCost

      public int getNetCost()
      Return the estimated cost of evaluating an expression. This is a very crude measure based on the syntactic form of the expression (we have no knowledge of data values). We take the cost of evaluating a simple scalar comparison or arithmetic expression as 1 (one), and we assume that a sequence has length 5. The resulting estimates may be used, for example, to reorder the predicates in a filter expression so cheaper predicates are evaluated first.
      Overrides:
      getNetCost in class Expression
      Returns:
      the intrinsic cost of this operation, excluding the costs of evaluating the operands

    • 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 - if evaluation fails

    • checkArguments

      protected void checkArguments(ExpressionVisitor visitor) throws XPathException
      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
      Throws:
      XPathException - if the arguments are incorrect

    • checkArgumentCount

      protected void checkArgumentCount(int min, int max) throws XPathException
      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
      Throws:
      XPathException - if the number of arguments is out of range

    • getImplementationMethod

      public int getImplementationMethod()
      An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). This method indicates which of these methods is provided directly. The other methods will always be available indirectly, using an implementation that relies on one of the other methods.
      Specified by:
      getImplementationMethod in class Expression
      Returns:
      the implementation method, for example Expression.ITERATE_METHOD or Expression.EVALUATE_METHOD or Expression.PROCESS_METHOD

    • plural

      public static String plural(int num, String thing)
      Utility routine used in constructing error messages: get the word "argument" or "arguments"
      Parameters:
      num - the number of arguments
      thing - the string "argument" or "parameter"
      Returns:
      the singular or plural phrase for N arguments or parameters.

    • 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.

    • getExpressionName

      public String getExpressionName()
      Get a name identifying the kind of expression, in terms meaningful to a user.
      Overrides:
      getExpressionName in class Expression
      Returns:
      a name identifying the kind of expression, in terms meaningful to a user. The name will always be in the form of a lexical XML QName, and should match the name used in explain() output displaying the expression.

    • 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
      Returns:
      a representation of the expression as a string

    • toShortString

      public String toShortString()
      Produce a short string identifying the expression for use in error messages
      Overrides:
      toShortString in class Expression
      Returns:
      a short string, sufficient to identify the expression

    • export

      public void export(ExpressionPresenter out) throws XPathException
      Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.
      Specified by:
      export in interface ExportAgent
      Specified by:
      export in class Expression
      Parameters:
      out - the expression presenter used to display the structure
      Throws:
      XPathException - if the export fails, for example if an expression is found that won't work in the target environment.

    • equals

      public boolean equals(Object o)
      Determine whether two expressions are equivalent
      Overrides:
      equals in class Expression
      Parameters:
      o - the other operand; the result is false if this is not an Expression
      Returns:
      true if the other operand is an expression and if it can be determined that the two expressions are equivalent, in the sense that they will always return the same result.

    • computeHashCode

      protected int computeHashCode()
      Get hashCode in support of equals() method
      Overrides:
      computeHashCode in class Expression
      Returns:
      a computed hash code

    • iterate

      public SequenceIterator iterate(XPathContext context) throws XPathException
      Return an Iterator to iterate over the values of a sequence. The value of every expression can be regarded as a sequence, so this method is supported for all expressions. This default implementation handles iteration for expressions that return singleton values: for non-singleton expressions, the subclass must provide its own implementation.
      Overrides:
      iterate in class Expression
      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

    • evaluateItem

      public Item evaluateItem(XPathContext context) throws XPathException
      Description copied from class: Expression
      Evaluate an expression as a single item. This always returns either a single Item or null (denoting the empty sequence). No conversion is done. This method should not be used unless the static type of the expression is a subtype of "item" or "item?": that is, it should not be called if the expression may return a sequence. There is no guarantee that this condition will be detected.
      Overrides:
      evaluateItem in class Expression
      Parameters:
      context - The context in which the expression is to be evaluated
      Returns:
      the node or atomic value that results from evaluating the expression; or null to indicate that the result is an empty sequence
      Throws:
      XPathException - if any dynamic error occurs evaluating the expression

    • adjustRequiredType

      public boolean adjustRequiredType(JavaExternalObjectType requiredType) throws XPathException
      When a call to a Java extension function appears in a context where there the required type is a Java external object (typically an xsl:variable with a declared type, or as an argument to another Java extension function), notify this required type so that the process of converting the result to an XDM value can be short-circuited.
      Parameters:
      requiredType - the required type of the result of the function, determined by the context in which the function call appears
      Returns:
      Ok if the type has been successfully adjusted
      Throws:
      XPathException - if the required return type is incompatible with the type actually returned by the Java method