Class Concat

All Implemented Interfaces:
Callable, PushableFunction, FunctionItem, GroundedValue, Item, Sequence

public class Concat extends SystemFunction implements PushableFunction
Implementation of the fn:concat() function
  • Constructor Details

    • Concat

      public Concat()
  • Method Details

    • resultIfEmpty

      protected Sequence resultIfEmpty(int arg)
      Description copied from class: SystemFunction
      Ask if the function always returns a known result when one of the arguments is an empty sequence
      Overrides:
      resultIfEmpty in class SystemFunction
      Parameters:
      arg - the argument whose value is an empty sequence (counting from zero)
      Returns:
      the value to be returned when this argument is an empty sequence, or null if unknown / not applicable
    • getFunctionItemType

      public FunctionItemType getFunctionItemType()
      Get the item type of the function item
      Specified by:
      getFunctionItemType in interface FunctionItem
      Overrides:
      getFunctionItemType in class SystemFunction
      Returns:
      the function item's type
    • makeOptimizedFunctionCall

      public Expression makeOptimizedFunctionCall(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo, Expression... arguments) throws XPathException
      Allow the function to create an optimized call based on the values of the actual arguments
      Overrides:
      makeOptimizedFunctionCall in class SystemFunction
      Parameters:
      visitor - the expression visitor
      contextInfo - information about the context item
      arguments - the supplied arguments to the function call. Note: modifying the contents of this array should not be attempted, it is likely to have no effect.
      Returns:
      either a function call on this function, or an expression that delivers the same result, or null indicating that no optimization has taken place
      Throws:
      XPathException - if an error is detected
    • call

      public StringValue call(XPathContext context, Sequence[] arguments) throws XPathException
      Description copied from interface: Callable
      Call the Callable.
      Specified by:
      call in interface Callable
      Parameters:
      context - the dynamic evaluation context
      arguments - the values of the arguments, supplied as Sequences.

      Generally it is advisable, if calling iterate() to process a supplied sequence, to call it only once; if the value is required more than once, it should first be converted to a GroundedValue by calling the utility method SequenceTool.toGroundedValue().

      If the expected value is a single item, the item should be obtained by calling Sequence.head(): it cannot be assumed that the item will be passed as an instance of Item or AtomicValue.

      It is the caller's responsibility to perform any type conversions required to convert arguments to the type expected by the callee. An exception is where this Callable is explicitly an argument-converting wrapper around the original Callable.

      Returns:
      the result of the evaluation, in the form of a Sequence. It is the responsibility of the callee to ensure that the type of result conforms to the expected result type.
      Throws:
      XPathException - if a dynamic error occurs during the evaluation of the expression
    • process

      public void process(Outputter destination, XPathContext context, Sequence[] arguments) throws XPathException
      Description copied from interface: PushableFunction
      Evaluate the function in "push" mode
      Specified by:
      process in interface PushableFunction
      Parameters:
      destination - the destination for the function result
      context - the dynamic evaluation context
      arguments - the supplied arguments to the function
      Throws:
      XPathException - if a dynamic error occurs during the evaluation
    • getRequiredType

      public SequenceType getRequiredType(int arg)
      Get the required type of the nth argument
      Overrides:
      getRequiredType in class SystemFunction
      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