# AtomicSequenceConverter
Keywords: net.sf.saxon.expr.AtomicSequenceConverter class

## net.sf.saxon.expr
Class AtomicSequenceConverter

    java.lang.Object
      net.sf.saxon.expr.Expression
          net.sf.saxon.expr.UnaryExpression
              net.sf.saxon.expr.AtomicSequenceConverter

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

    public final class AtomicSequenceConverter

extends UnaryExpression

An AtomicSequenceConverter is an expression that performs a cast on each member of a supplied sequence

See Also:
  Serialized Form

Field Summary

Fields inherited from class net.sf.saxon.expr.Expression
`EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD`

Constructor Summary
`AtomicSequenceConverter(Expression sequence, AtomicType requiredItemType)` Constructor

Method Summary
`int` `computeCardinality()` Determine the static cardinality of the expression
`int` `computeSpecialProperties()` Determine the special properties of this expression
`boolean` `equals(Object other)` Is this expression the same as another expression?
`Item` `evaluateItem(XPathContext context)` Evaluate as an Item.
`ItemType` `getItemType(TypeHierarchy th)` Determine the data type of the items returned by the expression, if possible
`AtomicType` `getRequiredPrimitiveType()` Get the required (target) primitive type
`SequenceIterator` `iterate(XPathContext context)` Iterate over the sequence of values
`Expression` `simplify(StaticContext env)` Simplify an expression
`Expression` `typeCheck(StaticContext env, ItemType contextItemType)` Type-check the expression

Methods inherited from class net.sf.saxon.expr.UnaryExpression
`display, getBaseExpression, hashCode, iterateSubExpressions, optimize, promote, replaceSubExpression`

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

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

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

Constructor Detail

### AtomicSequenceConverter

    public AtomicSequenceConverter(Expression sequence,
                                   AtomicType requiredItemType)

  Constructor

  Parameters:
    `sequence` - this must be a sequence of atomic values. This is not checked; a ClassCastException will occur if the precondition is not satisfied.
    `requiredItemType` - the item type to which all items in the sequence should be converted, using the rules for "cast as".

Method Detail

### getRequiredPrimitiveType

    public AtomicType getRequiredPrimitiveType()

  Get the required (target) primitive type

### simplify

    public Expression simplify(StaticContext env)
                        throws XPathException

  Simplify an expression

  Overrides:
    `simplify` in class `UnaryExpression`
  Returns:
    the simplified expression
  Throws:
    `XPathException` - if an error is discovered during expression rewriting

### typeCheck

    public Expression typeCheck(StaticContext env,
                                ItemType contextItemType)
                         throws XPathException

  Type-check the expression

  Overrides:
    `typeCheck` in class `UnaryExpression`
  Parameters:
    `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 to perform necessary run-time type checks, and to perform other type-related optimizations
  Throws:
    `StaticError` - if an error is discovered during this phase (typically a type error)
    `XPathException`

### computeSpecialProperties

    public int computeSpecialProperties()

  Determine the special properties of this expression

  Overrides:
    `computeSpecialProperties` in class `UnaryExpression`
  Returns:
    `StaticProperty.NON_CREATIVE`.

### iterate

    public SequenceIterator iterate(XPathContext context)
                             throws XPathException

  Iterate over the sequence of values

  Specified by:
    `iterate` in interface `SequenceIterable`
  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

  Evaluate as an Item. This should only be called if the AtomicSequenceConverter has cardinality zero-or-one

  Specified by:
    `evaluateItem` in interface `EvaluableItem`
  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

### getItemType

    public ItemType getItemType(TypeHierarchy th)

  Determine the data type of the items returned by the expression, if possible

  Overrides:
    `getItemType` in class `UnaryExpression`
  Parameters:
    `th` -
  Returns:
    a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER, Type.NODE, or Type.ITEM (meaning not known in advance)

### computeCardinality

    public int computeCardinality()

  Determine the static cardinality of the expression

  Overrides:
    `computeCardinality` in class `UnaryExpression`

### equals

    public boolean equals(Object other)

  Is this expression the same as another expression?

  Overrides:
    `equals` in class `UnaryExpression`

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