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com.icl.saxon.expr
Class Value

java.lang.Object

  |

  +--com.icl.saxon.expr.Expression

        |

        +--com.icl.saxon.expr.Value
Direct Known Subclasses:
BooleanValue, NodeSetValue, NumericValue, ObjectValue, StringValue
public abstract class Value
extends Expression

A value is the result of an expression but it is also an expression in its own right

Field Summary
static int ANY
           
static int BOOLEAN
          Constants denoting the data types of an expression or value
static int NODESET
           
static int NUMBER
           
static int OBJECT
           
static int STRING
           
 
Fields inherited from class com.icl.saxon.expr.Expression
staticContext
 
Constructor Summary
Value()
           
 
Method Summary
abstract  boolean asBoolean()
          Convert the value to a Boolean
abstract  double asNumber()
          Convert the value to a Number
abstract  java.lang.String asString()
          Convert the value to a String value
 boolean compare(int operator, Value other)
          Test how a Value compares to another Value under a relational comparison.
abstract  int conversionPreference(java.lang.Class required)
          Get conversion preference for this value to a Java class.
abstract  java.lang.Object convertToJava(java.lang.Class target)
          Convert to Java object (for passing to external functions)
 boolean equals(Value other)
          Test whether two values are equal.
 Value evaluate(Context context)
          Evaluate the Value.
 int getDependencies()
          Determine which aspects of the context the expression depends on.
protected static int inverse(int operator)
          Return the inverse of a relational operator, so that "a op b" can be rewritten as "b inverse(op) a"
 boolean notEquals(Value other)
          Test whether two values are not-equal.
protected  boolean numericCompare(int operator, double x, double y)
           
 Expression reduce(int dependencies, Context context)
          Perform a partial evaluation of the expression, by eliminating specified dependencies on the context.
 Expression simplify()
          Simplify an expression
static double stringToNumber(java.lang.String s)
          Static method to convert strings to numbers.
 
Methods inherited from class com.icl.saxon.expr.Expression
containsReferences, display, enumerate, evaluateAsBoolean, evaluateAsNodeSet, evaluateAsNumber, evaluateAsString, getDataType, getStaticContext, indent, isContextDocumentNodeSet, make, outputStringValue, setStaticContext, usesCurrent
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

BOOLEAN

public static final int BOOLEAN
Constants denoting the data types of an expression or value

NUMBER

public static final int NUMBER

STRING

public static final int STRING

NODESET

public static final int NODESET

OBJECT

public static final int OBJECT

ANY

public static final int ANY
Constructor Detail

Value

public Value()
Method Detail

stringToNumber

public static double stringToNumber(java.lang.String s)
Static method to convert strings to numbers. Might as well go here as anywhere else.
Parameters:
s - the String to be converted
Returns:
a double representing the value of the String; if it cannot be converted, return NaN (as required by the XSL specification)

evaluate

public Value evaluate(Context context)
               throws XPathException
Evaluate the Value. Null operation, because it has already been evaluated
Overrides:
evaluate in class Expression
Parameters:
context - The context (not used)
Returns:
the value, unchanged

simplify

public Expression simplify()
Simplify an expression
Overrides:
simplify in class Expression
Returns:
the simplified expression

getDependencies

public int getDependencies()
Determine which aspects of the context the expression depends on. The result is a bitwise-or'ed value composed from constants such as Context.VARIABLES and Context.CURRENT_NODE
Overrides:
getDependencies in class Expression

asString

public abstract java.lang.String asString()
                                   throws XPathException
Convert the value to a String value
Returns:
the value converted to a String

asNumber

public abstract double asNumber()
                         throws XPathException
Convert the value to a Number
Returns:
the value converted to a String

asBoolean

public abstract boolean asBoolean()
                           throws XPathException
Convert the value to a Boolean
Returns:
the value converted to a Boolean

equals

public boolean equals(Value other)
               throws XPathException
Test whether two values are equal. See the XSL specification: if either operand is a nodeset, they are compared as nodesets; else if either is a boolean, they are compared as booleans; else if either operand is a number, they are compared as numbers; else they are compared as strings.
Returns:
a boolean giving the value of the expression, evaluated in the current context

notEquals

public boolean notEquals(Value other)
                  throws XPathException
Test whether two values are not-equal. Note that a!=b means the same as !(a=b) except where either a or b is a nodeset.
Returns:
a boolean giving the value of the expression, evaluated in the current context

compare

public boolean compare(int operator,
                       Value other)
                throws XPathException
Test how a Value compares to another Value under a relational comparison. Note that the method is overridden for NodeSetValue
Parameters:
operator - The comparison operator, one of Tokenizer.LE, Tokenizer.LT, Tokenizer.GE, Tokenizer.GT, Tokenizer.EQUALS, Tokenizer.NE.

inverse

protected static final int inverse(int operator)
Return the inverse of a relational operator, so that "a op b" can be rewritten as "b inverse(op) a"

numericCompare

protected final boolean numericCompare(int operator,
                                       double x,
                                       double y)

reduce

public Expression reduce(int dependencies,
                         Context context)
Perform a partial evaluation of the expression, by eliminating specified dependencies on the context.
Overrides:
reduce in class Expression
Parameters:
dependencies - The dependencies to be removed
context - The context to be used for the partial evaluation
Returns:
a new expression that does not have any of the specified dependencies

convertToJava

public abstract java.lang.Object convertToJava(java.lang.Class target)
                                        throws XPathException
Convert to Java object (for passing to external functions)
Parameters:
target - The class required by the external function
Returns:
an object of the target class

conversionPreference

public abstract int conversionPreference(java.lang.Class required)
Get conversion preference for this value to a Java class. A low result indicates higher preference.
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