LoopLifter

java.lang.Object
- net.sf.saxon.expr.parser.LoopLifter

```
public class LoopLifter
extends java.lang.Object
```
Class to handle loop-lifting optimization, that is, extraction of subexpressions appearing within a loop when there is no dependency on the controlling variable of the loop. This handles both focus-dependent loops (such as xsl:for-each) and variable-dependent loops (such as XPath for-expressions), and also takes into account specialist loops such as xsl:for-each-group, xsl:merge, and xsl:analyze-string. The class is instantiated to perform optimization of a component such as a function or template, and it contains temporary instance-level data pertaining to that function or template.

Constructor Summary

Constructors
Constructor Description

LoopLifter(Expression root, Configuration config, boolean streaming)

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`void`	`gatherInfo(Expression exp)`	Gather information about an expression.
`Expression`	`getRoot()`
`static Expression`	`process(Expression exp, ExpressionVisitor visitor, ContextItemStaticInfo contextInfo)`	Apply loop-lifting to an expression (typically the body of a template or function)

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

- Constructor Detail
  - LoopLifter
```
public LoopLifter(Expression root,
                  Configuration config,
                  boolean streaming)
```
- Method Detail
  - process
```
public static Expression process(Expression exp,
                                 ExpressionVisitor visitor,
                                 ContextItemStaticInfo contextInfo)
                          throws XPathException
```
    Apply loop-lifting to an expression (typically the body of a template or function)
    
    Parameters:
    
    exp - the expression to which loop lifting is applied
    
    visitor - the expression visitor
    
    contextInfo - the static type of the context item
    
    Returns:
    
    the optimized expression
    
    Throws:
    
    XPathException - if any error occurs
  - getRoot
```
public Expression getRoot()
```
  - gatherInfo
```
public void gatherInfo(Expression exp)
```
    Gather information about an expression. The information (in the form of an ExpInfo object) is added to the expInfoMap, which is indexed by expression.
    
    Parameters:
    
    exp - the expression for which information is required