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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

  See Also:
    Constant Field Values

### NUMBER

    public static final int NUMBER

See Also:
  Constant Field Values

### STRING

    public static final int STRING

See Also:
  Constant Field Values

### NODESET

    public static final int NODESET

See Also:
  Constant Field Values

### OBJECT

    public static final int OBJECT

See Also:
  Constant Field Values

### ANY

    public static final int ANY

See Also:
  Constant Field Values

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

  Specified by:
    `evaluate` in class `Expression`
  Parameters:
    `context` - The context (not used)
  Returns:
    the value, unchanged
    `XPathException`

### 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

  Specified by:
    `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
    `XPathException`

### asNumber

    public abstract double asNumber()
                             throws XPathException

  Convert the value to a Number

  Returns:
    the value converted to a String
    `XPathException`

### asBoolean

    public abstract boolean asBoolean()
                               throws XPathException

  Convert the value to a Boolean

  Returns:
    the value converted to a Boolean
    `XPathException`

### 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
    `XPathException`

### 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
    `XPathException`

### 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.
    `XPathException`

### 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.

  Specified by:
    `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
    `XPathException`

### 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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