This document discusses refactoring and metaprogramming. It provides an overview of topics including refactoring basics, refactoring tools in Squeak, and the implementation of the refactoring engine. The refactoring engine uses an abstract syntax tree to represent code and tree rewriting to specify transformations. Reflection is discussed, noting that while refactoring changes a system using itself, the refactoring engine builds its own abstraction layer rather than using the system's reflective capabilities.

1. Metaprogramming and Reflection Refactoring Universit ät Bern Marcus Denker Hasso-Plattner-Institut Potsdam Software Architecture Group Prof. Dr. Robert Hirschfeld http://www.swa.hpi.uni-potsdam.de WS 2006/2007

5. Typical Refactorings extract code in new method abstract variable move method to component create accessors add parameter to method pull variable up push method up push variable down push method down remove variable remove method remove class rename variable rename method rename class add variable to class add method to class add (sub)class to hierarchy Attribute Method Class

21. A Simple AST explore it RBParser parseExpression: '3+4'

22. A Simple Visitor RBProgramNodeVisitor new visitNode: tree Does nothing except walk through the tree

23. More Complete Visitor RBProgramNodeVisitor subclass: #TestVisitor instanceVariableNames: 'literals' classVariableNames: '' poolDictionaries: '' category: 'Compiler-AST-Visitors' TestVisitor>> acceptLiteralNode: aLiteralNode literals add: aLiteralNode value. TestVisitor>> initialize literals := Set new. TestVisitor>> literals ^literals tree := RBParser parseExpression: '3 + 4'. (TestVisitor new visitNode: tree) literals a Set(3 4)

26. Meta Variables All Meta Variables begin with ` `#literal literal # `.Statement statement . | `@Temps | `@.statements list @ ``@object foo recurse into ` Example Type Character

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35. Why not this?