1. CS 614: Theory and Construction of Compilers Lecture 10 Fall 2003 Department of Computer Science University of Alabama Joel Jones

2. Lecture 10©2003 Joel Jones2 Overview Requirements for a refactoring tool Don Roberts and John Brant in Refactoring: Improving the Design of Existing Code by Martin Fowler Architecture of the smalltalk refactoring browser Don Roberts, Practical Analysis for Refactoring, University of Illinois, Department of Computer Science Ph.D. dissertation.

3. Lecture 10©2003 Joel Jones3 Technical Criteria for a Refactoring Tool Program database Must be able to search all of the code for a program Parse trees Refactorings are source-to-source translations, so parse tree must be fairly complete Accuracy Refactoring shouldn’t change behavior

4. Lecture 10©2003 Joel Jones4 Practical Criteria for a Refactoring Tool Speed Must be fast enough for programmer to use it Undo Allows more experimentation Is source code control system enough? Integrated with tools Otherwise, programmers won’t use it

5. Lecture 10©2003 Joel Jones5 The Transformation Framework Refactorings—base class, implements preconditions and performRefactoring Conditions—analyses that are shared by all refactorings Parser—preserves non-semantic information, recognizes pattern variables, uses Builder pattern

6. Lecture 10©2003 Joel Jones6 The Transformation Framework (cont.) Tree rewriter—performs matches (input: AST with potential named pattern variables and standard AST) and rewrites (input: two pattern ASTs with shared patterns variables and standard AST), uses Visitor pattern Formatter—uses Visitor over ASTs and BRFormatter class to produce source code following formatting guidelines Change objects—represent low-level changes to code, uses Command pattern to support undo

7. Lecture 10©2003 Joel Jones7 Reading Next Class Muchnick, chapter 4 through and including section 4.6