CastExpression

java.lang.Object
- net.sf.saxon.expr.Expression
- - net.sf.saxon.expr.UnaryExpression
  - - net.sf.saxon.expr.CastExpression

All Implemented Interfaces:

java.io.Serializable, javax.xml.transform.SourceLocator, LocationProvider, SaxonLocator, EvaluableItem, SequenceIterable, InstructionInfo, org.xml.sax.Locator
```
public final class CastExpression
extends UnaryExpression
```
Cast Expression: implements "cast as data-type ( expression )". It also allows an internal cast, which has the same semantics as a user-requested cast, but maps an empty sequence to an empty sequence.

See Also:

Serialized Form

Field Summary
- Fields inherited from class net.sf.saxon.expr.Expression
  EVALUATE_METHOD, ITERATE_METHOD, locationId, PROCESS_METHOD, staticProperties
- Fields inherited from class net.sf.saxon.expr.UnaryExpression
  operand

Constructor Summary

Constructors
Constructor Description

CastExpression(Expression source, AtomicType target, boolean allowEmpty)
Create a cast expression

Constructors
Constructor	Description
`CastExpression(Expression source, AtomicType target, boolean allowEmpty)`	Create a cast expression

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`boolean`	`allowsEmpty()`	Ask whether the expression accepts an empty sequence as input (producing an empty sequence as output)
`static AtomicValue`	`castStringToQName(java.lang.CharSequence operand, AtomicType targetType, StaticContext env)`	Evaluate the "pseudo-cast" of a string literal to a QName or NOTATION value.
`int`	`computeCardinality()`	Get the static cardinality of the expression
`int`	`computeSpecialProperties()`	Determine the special properties of this expression
`Expression`	`copy()`	Copy an expression.
`boolean`	`equals(java.lang.Object other)`	Is this expression the same as another expression?
`Item`	`evaluateItem(XPathContext context)`	Evaluate the expression
`void`	`explain(ExpressionPresenter out)`	Diagnostic print of expression structure.
`ItemType`	`getItemType(TypeHierarchy th)`	Get the static type of the expression
`AtomicType`	`getTargetPrimitiveType()`	Get the primitive base type of the target type of the cast
`AtomicType`	`getTargetType()`	Get the target type (the result type)
`static boolean`	`isPossibleCast(int source, int target)`	Determine whether casting from a source type to a target type is possible
`boolean`	`isUpCast()`	Ask whether this is a cast to a supertype of the original type
`Expression`	`simplify(ExpressionVisitor visitor)`	Simplify the expression
`boolean`	`targetIsDerived()`	Ask whether the target type is a derived type (not a primitive type)
`java.lang.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.
`Expression`	`typeCheck(ExpressionVisitor visitor, ItemType contextItemType)`	Type-check the expression

Methods inherited from class net.sf.saxon.expr.Expression
addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, display, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluatePendingUpdates, explain, findParentOf, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, isUpdatingExpression, iterate, iterateEvents, markTailFunctionCalls, process, resetLocalStaticProperties, setContainer, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, typeError

Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait

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

- Constructor Detail
  - CastExpression
```
public CastExpression(Expression source,
                      AtomicType target,
                      boolean allowEmpty)
```
    Create a cast expression
    
    Parameters:
    
    source - expression giving the value to be converted
    
    target - the type to which the value is to be converted
    
    allowEmpty - true if the expression allows an empty sequence as input, producing an empty sequence as output. If false, an empty sequence is a type error.
- Method Detail
  - isPossibleCast
```
public static boolean isPossibleCast(int source,
                                     int target)
```
    Determine whether casting from a source type to a target type is possible
    
    Parameters:
    
    source - a primitive type (one that has an entry in the casting table)
    
    target - another primitive type
    
    Returns:
    
    true if the entry in the casting table is either "Y" (casting always succeeds) or "M" (casting allowed but may fail for some values)
  - getTargetPrimitiveType
```
public AtomicType getTargetPrimitiveType()
```
    Get the primitive base type of the target type of the cast
    
    Returns:
    
    the primitive type of the target type
  - getTargetType
```
public AtomicType getTargetType()
```
    Get the target type (the result type)
    
    Returns:
    
    the target type
  - allowsEmpty
```
public boolean allowsEmpty()
```
    Ask whether the expression accepts an empty sequence as input (producing an empty sequence as output)
    
    Returns:
    
    true if an empty sequence is accepted
  - targetIsDerived
```
public boolean targetIsDerived()
```
    Ask whether the target type is a derived type (not a primitive type)
    
    Returns:
    
    true if the target type is a derived type
  - isUpCast
```
public boolean isUpCast()
```
    Ask whether this is a cast to a supertype of the original type
    
    Returns:
    
    true if this is an upcast. This means the value stays unchanged and only the type label changes
  - simplify
```
public Expression simplify(ExpressionVisitor visitor)
                    throws XPathException
```
    Simplify the expression
    
    Overrides:
    
    simplify in class UnaryExpression
    
    Parameters:
    
    visitor - an expression visitor
    
    Returns:
    
    the simplified expression
    
    Throws:
    
    XPathException - if an error is discovered during expression rewriting
  - typeCheck
```
public Expression typeCheck(ExpressionVisitor visitor,
                            ItemType contextItemType)
                     throws XPathException
```
    Type-check the expression
    
    Overrides:
    
    typeCheck in class UnaryExpression
    
    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 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)
  - computeCardinality
```
public int computeCardinality()
```
    Get the static cardinality of the expression
    
    Overrides:
    
    computeCardinality in class UnaryExpression
    
    Returns:
    
    the computed cardinality, as one of the values StaticProperty.ALLOWS_ZERO_OR_ONE, StaticProperty.EXACTLY_ONE, StaticProperty.ALLOWS_ONE_OR_MORE, StaticProperty.ALLOWS_ZERO_OR_MORE
  - getItemType
```
public ItemType getItemType(TypeHierarchy th)
```
    Get the static type of the expression
    
    Overrides:
    
    getItemType in class UnaryExpression
    
    Parameters:
    
    th - the type hierarchy cache
    
    Returns:
    
    the item type of the items in the result sequence, insofar as this is known statically.
  - computeSpecialProperties
```
public int computeSpecialProperties()
```
    Determine the special properties of this expression
    
    Overrides:
    
    computeSpecialProperties in class UnaryExpression
    
    Returns:
    
    StaticProperty.NON_CREATIVE.
  - copy
```
public Expression copy()
```
    Copy an expression. This makes a deep copy.
    
    Specified by:
    
    copy in class Expression
    
    Returns:
    
    the copy of the original expression
  - evaluateItem
```
public Item evaluateItem(XPathContext context)
                  throws XPathException
```
    Evaluate the expression
    
    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
  - equals
```
public boolean equals(java.lang.Object other)
```
    Is this expression the same as another expression?
    
    Overrides:
    
    equals in class UnaryExpression
  - toString
```
public java.lang.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 UnaryExpression
  - explain
```
public void explain(ExpressionPresenter out)
```
    Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.
    
    Overrides:
    
    explain in class UnaryExpression
    
    Parameters:
    
    out - the expression presenter used to display the structure
  - castStringToQName
```
public static AtomicValue castStringToQName(java.lang.CharSequence operand,
                                            AtomicType targetType,
                                            StaticContext env)
                                     throws XPathException
```
    Evaluate the "pseudo-cast" of a string literal to a QName or NOTATION value. This can only happen at compile time
    
    Parameters:
    
    operand - the value to be converted
    
    targetType - the type to which it is to be converted
    
    env - the static context
    
    Returns:
    
    the QName or NOTATION value that results from casting the string to a QName. This will either be a QNameValue or a derived AtomicValue derived from QName or NOTATION
    
    Throws:
    
    XPathException

Class CastExpression

Field Summary

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

Fields inherited from class net.sf.saxon.expr.UnaryExpression

Constructor Summary

Method Summary

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

Methods inherited from class java.lang.Object

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

Constructor Detail

CastExpression

Method Detail

isPossibleCast

getTargetPrimitiveType

getTargetType

allowsEmpty

targetIsDerived

isUpCast

simplify

typeCheck

computeCardinality

getItemType

computeSpecialProperties

copy

evaluateItem

equals

toString

explain

castStringToQName