## net.sf.saxon.functions
Class SystemFunction

    java.lang.Object
      net.sf.saxon.expr.Expression
          net.sf.saxon.expr.FunctionCall
              net.sf.saxon.functions.SystemFunction

All Implemented Interfaces:
  Serializable, SourceLocator, Container, EvaluableItem, SequenceIterable, InstructionInfoProvider

Direct Known Subclasses:
  Adjust, Aggregate, Available, BaseURI, BooleanFn, CodepointEqual, CodepointsToString, CollatingFunction, Collection, CompileTimeFunction, Component, Concat, Current, CurrentDateTime, CurrentGroup, DateTimeConstructor, Doc, DocAvailable, Document, DynamicFunctionCall, Error, EscapeURI, Evaluate, Existence, Find, ForceCase, ForEachGroupFunction, FormatDate, FormatNumber2, Id, Idref, InScopePrefixes, Insert, KeyFn, Lang, Last, Matches, NamePart, NamespaceForPrefix, Nilled, NormalizeSpace, NormalizeUnicode, NumberFn, Parse, Position, QNameFn, RegexGroup, Remove, Replace, ResolveQName, ResolveURI, Root, Rounding, Serialize, StringFn, StringJoin, StringLength, StringToCodepoints, Subsequence, Substring, SystemProperty, Tokenize, Trace, Translate, TreatFn, Try, UnparsedEntity, UnparsedText

    public abstract class SystemFunction

extends FunctionCall

Abstract superclass for 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
`SystemFunction()`

Method Summary
`void` `checkArguments(StaticContext env)` Method called during static type checking
`int` `computeCardinality()` Determine the cardinality of the function.
`int` `computeSpecialProperties()` Determine the special properties of this expression.
`void` `display(int level, PrintStream out, Configuration config)` Diagnostic print of expression structure
`StandardFunction.Entry` `getDetails()` Get the details
`String` `getErrorCodeForTypeErrors()` Return the error code to be used for type errors.
`ItemType` `getItemType(TypeHierarchy th)` Determine the item type of the value returned by the function
`static void` `main(String[] args)` The main() method of this class is not intended to be called, it merely tells the code inspection tools in IDEA that the constructors of each function class are actual entry points
`static FunctionCall` `makeSystemFunction(String name, int arity, NamePool pool)` Make a system function (one in the standard function namespace).
`Expression` `optimize(Optimizer opt, StaticContext env, ItemType contextItemType)` Perform optimisation of an expression and its subexpressions.
`void` `setDetails(StandardFunction.Entry entry)` Set the details of this type of function

Methods inherited from class net.sf.saxon.expr.FunctionCall
`getArguments, getDisplayName, getFunctionNameCode, getNumberOfArguments, iterateSubExpressions, preEvaluate, promote, replaceSubExpression, setArguments, setFunctionNameCode, simplify, typeCheck`

Methods inherited from class net.sf.saxon.expr.Expression

`adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, effectiveBooleanValue, evaluateAsString, evaluateItem, getCardinality, getColumnNumber, getContainingProcedure, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getLineNumber, getLocationId, getLocationProvider, getParentExpression, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasBadParentPointer, iterate, markTailFunctionCalls, process, resetStaticProperties, setLocationId, setParentExpression, setParentExpression, suppressValidation`

Methods inherited from class java.lang.Object
`equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### SystemFunction

    public SystemFunction()

Method Detail

### makeSystemFunction

    public static FunctionCall makeSystemFunction(String name,
                                                  int arity,
                                                  NamePool pool)

  Make a system function (one in the standard function namespace).

  Parameters:
    `name` - The local name of the function. It may also be a lexical QName for a recognized built-in function, e.g. saxon:evaluate, in which case the prefix is hard-coded.
  Returns:
    a FunctionCall that implements this function, if it exists, or null if the function is unknown.

### setDetails

    public void setDetails(StandardFunction.Entry entry)

  Set the details of this type of function

### getDetails

    public StandardFunction.Entry getDetails()

  Get the details

### checkArguments

    public void checkArguments(StaticContext env)
                        throws XPathException

  Method called during static type checking

  Throws:
    `XPathException`

### optimize

    public Expression optimize(Optimizer opt,
                               StaticContext env,
                               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 `FunctionCall`
  Parameters:
    `opt` - the optimizer in use. This provides access to supporting functions; it also allows different optimization strategies to be used in different circumstances.
    `env` - the static context of the expression
    `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:
    `StaticError` - if an error is discovered during this phase (typically a type error)
    `XPathException`

### 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(), ...

### getItemType

    public ItemType getItemType(TypeHierarchy th)

  Determine the item type of the value returned by the function

  Specified by:
    `getItemType` in class `Expression`
  Parameters:
    `th` -
  Returns:
    a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER, Type.NODE, or Type.ITEM (meaning not known at compile time)

### 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)

  Overrides:
    `computeSpecialProperties` in class `Expression`

### display

    public void display(int level,
                        PrintStream out,
                        Configuration config)

  Diagnostic print of expression structure

  Overrides:
    `display` in class `FunctionCall`
  Parameters:
    `level` - indentation level for this expression
    `out` - Output destination

### main

    public static void main(String[] args)
                     throws Exception

  The main() method of this class is not intended to be called, it merely tells the code inspection tools in IDEA that the constructors of each function class are actual entry points

  Throws:
    `Exception`

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