polyglot.visit
Class NodeScrambler

java.lang.Object
  polyglot.visit.NodeVisitor
      polyglot.visit.NodeScrambler

public class NodeScrambler
extends NodeVisitor

The NodeScrambler is test case generator of sorts. Since it is ofter useful to introduce ``random'' errors into source code, this class provides a way of doing so in a semi-structed manner. The process takes place in two phases. First, a "FirstPass" is made to collect a list of nodes and their parents. Then a second pass is made to randomly replace a branch of the tree with another suitable branch.

Nested Class Summary

class

NodeScrambler.FirstPass Scans throught the AST, create a list of all nodes present, along with the set of parents for each node in the tree.

Field Summary

protected java.util.LinkedList	currentParents
protected CodeWriter	cw
NodeScrambler.FirstPass	fp
protected java.util.LinkedList	nodes
protected java.util.HashMap	pairs
protected java.util.Random	ran
protected boolean	scrambled
protected long	seed

Constructor Summary

NodeScrambler()

NodeScrambler(long seed)
Create a new NodeScrambler with the given random number generator seed.

Method Summary

protected boolean	coinFlip()
long	getSeed()
Node	override(Node n) Given a tree rooted at n, the visitor has the option of overriding all traversal of the children of n.
protected Node	potentialScramble(Node n)

Methods inherited from class polyglot.visit.NodeVisitor

begin, enter, enter, finish, finish, leave, leave, override, toString, visitEdge

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

fp

public NodeScrambler.FirstPass fp

pairs

protected java.util.HashMap pairs

nodes

protected java.util.LinkedList nodes

currentParents

protected java.util.LinkedList currentParents

seed

protected long seed

ran

protected java.util.Random ran

scrambled

protected boolean scrambled

cw

protected CodeWriter cw

Constructor Detail

NodeScrambler

public NodeScrambler()

NodeScrambler

public NodeScrambler(long seed)

Create a new NodeScrambler with the given random number generator seed.

Method Detail

getSeed

public long getSeed()

override

public Node override(Node n)

Description copied from class: NodeVisitor

Given a tree rooted at n, the visitor has the option of overriding all traversal of the children of n. If no changes were made to n and the visitor wishes to prevent further traversal of the tree, then it should return n. If changes were made to the subtree, then the visitor should return a copy of n with appropriate changes. Finally, if the visitor does not wish to override traversal of the subtree rooted at n, then it should return null.

This method is typically called by the method override(parent, n). If a subclass overrides the method override(parent, n) then this method may not be called.

Overrides:

override in class NodeVisitor

Parameters:

n - The root of the subtree to be traversed.

Returns:

A node if normal traversal is to stop, null if it is to continue.

coinFlip

protected boolean coinFlip()

potentialScramble

protected Node potentialScramble(Node n)