Prev Class | Next Class | Frames | No Frames |
Summary: Nested | Field | Method | Constr | Detail: Nested | Field | Method | Constr |
java.lang.Object
com.icl.saxon.expr.Expression
public abstract class Expression
extends Object
Field Summary | |
protected StaticContext |
Method Summary | |
boolean |
|
abstract void |
|
NodeEnumeration | |
abstract Value | |
boolean |
|
NodeSetValue |
|
double |
|
String |
|
abstract int |
|
abstract int |
|
StaticContext |
|
protected static String |
|
boolean |
|
static Expression |
|
void |
|
abstract Expression | |
void |
|
Expression |
|
boolean |
|
public boolean containsReferences() throws XPathException
Determine whether the expression contains any references to variables
- Returns:
- true if so
public abstract void display(int level)
Diagnostic print of expression structure
public NodeEnumeration enumerate(Context context, boolean sorted) throws XPathException
Return an enumeration of nodes in a nodeset.
- Parameters:
context
- The context in which the expression is to be evaluatedsorted
- Indicates whether the nodes are required in document order. If this is false, they may come in any order, but there will be no duplicates.
- Throws:
XPathException
- when the expression does not return a nodeset.
public abstract Value evaluate(Context context) throws XPathException
Evaluate an expression.
- Parameters:
context
- The context in which the expression is to be evaluated
- Returns:
- the value of the expression, evaluated in the current context
public boolean evaluateAsBoolean(Context context) throws XPathException
Evaluate an expression as a Boolean.
The result of x.evaluateAsBoolean(c) must be equivalent to x.evaluate(c).asBoolean(); but optimisations are possible when it is known that a boolean result is required, especially in the case of a NodeSet.
- Parameters:
context
- The context in which the expression is to be evaluated
- Returns:
- the value of the expression, evaluated in the current context
public NodeSetValue evaluateAsNodeSet(Context context) throws XPathException
Evaluate an expression as a NodeSet.
- Parameters:
context
- The context in which the expression is to be evaluated
- Returns:
- the value of the expression, evaluated in the current context. Note that the result is not necessarily in document order; to get it into document order, call sort() on the result.
- Throws:
XPathException
- when the expression does not return a nodeset.
public double evaluateAsNumber(Context context) throws XPathException
Evaluate an expression as a Number.
The result of x.evaluateAsNumber(c) must be equivalent to x.evaluate(c).asNumber(); but optimisations are possible when it is known that a numeric result is required, especially in the case of a NodeSet.
- Parameters:
context
- The context in which the expression is to be evaluated
- Returns:
- the value of the expression, evaluated in the current context
public String evaluateAsString(Context context) throws XPathException
Evaluate an expression as a String.
The result of x.evaluateAsString(c) must be equivalent to x.evaluate(c).asString(); but optimisations are possible when it is known that a string result is required, especially in the case of a NodeSet.
- Parameters:
context
- The context in which the expression is to be evaluated
- Returns:
- the value of the expression, evaluated in the current context
public abstract int getDataType()
Determine the data type of the expression, if possible
- Returns:
- one of the values Value.STRING, Value.BOOLEAN, Value.NUMBER, Value.NODESET, Value.FRAGMENT, or Value.ANY (meaning not known in advance)
public abstract 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
public final StaticContext getStaticContext()
Determine the static context used when the expression was parsed
protected static String indent(int level)
Construct indent string, for diagnostic output
public boolean isContextDocumentNodeSet()
Determine, in the case of an expression whose data type is Value.NODESET, whether all the nodes in the node-set are guaranteed to come from the same document as the context node. Used for optimization.
public static Expression make(String expression, StaticContext env) throws XPathException
Parse an expression
- Parameters:
expression
- The expression (as a character string)env
- An object giving information about the compile-time context of the expression
- Returns:
- an object of type Expression
public void outputStringValue(Outputter out, Context context) throws TransformerException
Evaluate an expression as a String and write the result to the specified outputter.
- Parameters:
out
- The required outputtercontext
- The context in which the expression is to be evaluated
public abstract Expression reduce(int dependencies, Context context) throws XPathException
Perform a partial evaluation of the expression, by eliminating specified dependencies on the context.
- Parameters:
dependencies
- The dependencies to be removed, e.g. Context.VARIABLEScontext
- The context to be used for the partial evaluation
- Returns:
- a new expression (or Value) that does not have any of the specified dependencies
public final void setStaticContext(StaticContext sc)
Set the static context used when the expression was parsed
public Expression simplify() throws XPathException
Simplify an expression. Default implementation does nothing.
- Returns:
- the simplified expression
public boolean usesCurrent()
Determine whether the expression uses the current() function. This is an error if the expression is within a pattern