Method extraction is the process of separating out a subset of methods statements into another method and replacing their occurrence in the original method with a call. Program slicing is a method for automatically decomposing programs by analyzing their data flow and control flow. An example of a refactoring could be extract method figure 1. You read the code by modifying it, nudging it into a clearer, more readable state. Refactoring is intended to improve the design, structure, andor implementation of the software its nonfunctional attributes, while preserving the functionality of the software. Refactoring should be done as a series of small changes, each of which makes the existing code slightly better while still leaving the program in working order. Although i agree with that principle, i dont find it easy to. Browse the amazon editors picks for the best books of 2019, featuring our favorite reads in more than a dozen categories. This paper presents a interprocedural dynamic slicing for handling pointers in. Refactoring is meant as an improvement of the internal structure of a software system. Sep 30, 2012 refactoring is the process of taking existing code and changing it in some way to make it more readable and perhaps less complex. Each transformation called a refactoring does little, but a sequence of these transformations can produce a significant restructuring. Refactoring to patterns suggests that using patterns to improve an existing design is better than using patterns early in a new design. Each page dedicated to a refactoring is clearly marked, so refactoring is the process of rewriting software, without changing the way it functions, in order to improve.
Code refactoring is a disciplined way to restructure code, undertaken in order to improve some of the nonfunctional attributes of the software. The refactoring techniques in this group streamline methods, remove. Some of the goals of refactoring include increased readability, decreased coupling, and easier code reuse i. Improving the design of existing code addisonwesley object technology series book online at best prices in india on. Refactoring generally means to alter the way a piece of codemodule program is written without actually changing its functionality. Find a clump of code within the long method that goes well together, create a new method with a. Dont confuse it with rewriting though rewriting means starting again from scratch to create a new improved version, whereas refactoring is an incremental process of improving existing code by making changes to small parts, one at a time. Checklist of refactoring done right way the code should become cleaner. Over the last years, a great deal of ontologies of many different kinds and describing different domains has been created, and new methods and prototypes have.
Part of the communications in computer and information science book series. Program slicing is a method used by experienced computer programmers for abstracting from pro grams. Visaggioextracting reusable functions by flow graphbased program slicing trans. Decoupling a slice of code from its original context and making it into a.
Refactoring is a disciplined technique for restructuring an existing body of code, altering its internal structure without changing its external behavior its heart is a series of small behavior preserving transformations. However the cumulative effect of each of these transformations is quite significant. A specification driven slicing process for identifying reusable functions. Everyday low prices and free delivery on eligible orders. Common to all slicing related refactorings, as explored in this thesis, is the goal of improving. Its been wonderful to watch more and more people learn how to use refactoring to modify working code in a disciplined and effective manner. What are some good books on refactoringwriting better.
By ian spence, spct, chief scientist at ivar jacobson international. A program slice is a projection of the behavior from a software module that is needed to produce a. When i updated it eighteen years later, refactoring had become a regular tool for any skilled programmer. Its essence is applying a series of small behaviorpreserving transformations, each of which too small to be worth doing. Today, refactoring requires considerable design knowhow, but once tools become available, all programmers should be able to improve their code using refactoring techniques. Our updated entry in the 9th edition of the haskell communities report. Refactoring is a proven way to prevent software decay. Program slicing is a method used by experienced computer programmers for abstracting from programs. Automated methodextraction refactoring by using blockbased slicing. Refactoring to patterns is the marriage of refactoring the process of improving the design of existing code with patterns, the classic solutions to recurring design problems. The bulk of this book is a catalog of refactorings, but there is more to it as i will explain below. It is setup as a catalog of refactoring techniques. Using software metrics and program slicing for refactoring.
The filter panel at the left allows you to select the refactorings by keyword, and also by which books they appear in. Introduction refactoring is the process of changing a software system in such a way that it does not alter the external behavior of the code yet improves its internal structure. This article presents an approach that guides the refactoring. Pdf using program slicing to detect the dead code researchgate. Even if that had been correct, the paper is of the cheapest possible quality which means you can see the text of the next page through the page you are reading, something that makes reading source code, where punctuation really matters, much more difficult. Slicing is the process of extracting the statements of a program affecting a given computation. Enter your mobile number or email address below and well send. According to mark weiser, who introduced the concept of program slicing in the early eighties, a slice is the mental abstraction people make when they are. Program slicing is a technique to decompose programs depending on control flow and data flow amongst several lines of code in a program. Chamillard university of colorado at colorado springs refactoring can improve the quality of a software system as measured by coupling, cohesion, and cyclomatic complexity, but knowing which refactoring choices should be implemented is key. Starting from a subset of a program s behavior, slicing reduces that program to a minimal form which still produces that behavior. A decade ago refactoring was a word only known to a few people, mostly in the smalltalk community. Program slicing as decomplationprogram reconstruction technique. We take it for granted that advanced refactoring tools will somehow need program slicing techniques, and therefore we shall design a novel variant of common slicing approaches to t refactorings constraints.
Improving the design of existing code, renowned object technology mentor martin fowler breaks new ground, demystifying these master practices and demonstrating how software practitioners can realize the significant benefits of this new process. Refactoring is just a fancy way of describing a process in which you rewrite parts of your code to make them better. Much of refactoring is devoted to correctly composing methods. Pdf refactoring via program slicing and sliding researchgate. Improving the design of existing code is focused on oo programming lots of java examples and agile practices.
In most cases, excessively long methods are the root of all evil. The decomposition slicing technique is used to identify the live code, and refactoring techniques can also help in tide up the code design. Program slicing, metrics, and refactoring when considering options for refactor ing, a technique known as program slicing can be used to isolate portions of a software system. Usually, this would not affect a program, but if the program requirements include hard realtime constraints, this could cause a program to be incorrect. They build on a static program analysis technique called program slicing 38, which answers queries about the dependencies among a programs variables. For example, if your program constructs a string and the uses the java reflection. Identification of extract method refactoring opportunities.
Introduction to software engineeringtestingrefactoring. Refactoring is the process of changing the code of the software such that its internal design is improved without altering its observable behavior. In addition to discussing the various techniques of refactoring, the author provides a detailed catalog of more than seventy proven refactorings with helpful pointers that teach you when to apply them. Refactoring via program slicing and sliding ibm research. Indeed, most of the applications of program slicing require di erent properties of slices. Improving the design of existing code shows how refactoring can make objectoriented code simpler and easier to maintain. With code gathering tools, an analyst first selects a set of analysis results, which.
Improving the design of existing code addisonwesley signature series fowler 2 by fowler, martin isbn. Today refactoring requires considerable design knowhow, but once tools become available, all programmers should be able to improve their code using refactoring techniques. A program slice consists of the parts of a program that potentially affect the values computed at some point of interest, referred to as a slicing criterion. And one important aspect of this preparation is to slice up any of the targeted features that are too. Citeseerx document details isaac councill, lee giles, pradeep teregowda. Advanced topic rightsizing features for safe program. Starting from a subset of a programs behavior, slicing reduces that program to a minimal form which still produces that behavior. The mantra of refactoring is clean code and simple design. Refactoring interprocedural dynamic slicing for handling pointers. Refactoring improves code quality, reliability and maintainability throughout software life cycle. Improving the design of existing code, renowned object technology mentor martin fowler breaks new ground. Conditioned slicing is a generalization of static slicing and dynamic slicing. Potential advantages of refactoring may include improved. And one important aspect of this preparation is to slice up any of the targeted features that are too large to be.
This book arrived this morning and i was disappointed. Refactoring generally means to alter the way a piece of codemoduleprogram is written without actually changing its functionality. The example concerns a piece of software for run ning a video store, focusing on the. The resulting interaction leads to a program with a design that stays good as development continues. Program slicing for refactoring, static slicer using dynamic analyser 1. Its traditional to start books with an introduction. In contrast to static slices, dynamic slices are smaller in size as they extract statements for a. This is the book that im proudest of, in that its had a high impact on the world of software development.
Several development environments now automate many of the refactorings described in the book. Refactoring is a controlled technique for improving the design of an existing code base. Every day, my thoughts on what good code looks like changes. Common to all slicing related refactorings, as explored in this thesis, is the goal of improving reusability, comprehensibility and hence maintainability of existing code. This paper proposes a mechanism that automatically refactors methods of object oriented programs by using program slicing. Without refactoring you accrue technical debt, forget what portions of code do and create. If a method is too long, it should be decomposed, using this refactoring technique.
What are some good books on refactoringwriting better code. My 14 years of programming comes with a lot of baggage some might c. Problems and techniques code smells are surface indications that there are deeper problems in the system most refactoring techniques are fairly straightforward, and there is often really good tool support for these now in both the case of code smells and refactoring techniques, there are new ones being discovered all the time, so the list of names is fairly long. When software developers add new features to a program, the code degrades because the original program was not designed with the extra features in mind. Find a clump of code within the long method that goes well together, create a new method with a descriptive name and move the code into the new method.
Using program slicing to detect the dead code ieee conference. Refactoring has become a fullfledged part of the software development lexicon sadly also leading to misuse. Chris gave a talk at the fp group refactoring functional programs and program slicing. Improving the design of existing code, martin fowler. Improving the design of existing code is one of those amazing books that every professional developer should have on their book shelf.
Most refactoring techniques are fairly straightforward, and there is often really good tool support for these now in both the case of code smells and refactoring techniques, there are new ones being discovered all the time, so the list of names is fairly long. One of the key activities that will help make your safe program a success is the careful preparation of your features prior to program increment pi planning. Ive been programming professionally for 14 years, and i am still learning every day. The term refactoring specifically refers to a common activity in programming and software maintenance. Refactoring is the controllable process of systematically improving your code without writing new functionality. An intuitive definition is that a safe refactoring is one that doesnt break a program. The noun refactoring refers to one particular behaviorpreserving transformation, such as extract method or introduce parameter. Keywordsprogram slicing, decomposition slicing, dead code. A variable, the desired program point, and a condition of interest form a slicing cr. Rightsizing features for safe program increments by ian spence, spct, chief scientist at ivar jacobson international one of the key activities that will help make your safe program a success is the careful preparation of your features prior to program increment pi planning. A slice extraction refactoring acm digital library. The key thing to note, is that when the code is changed, is does not affect the underlying functionality of the code itself. I wrote the original edition in 2000 when refactoring was a littleknown technique.
Program slicing as decomplationprogram reconstruction. Starting from a subset of a programs behavior, slicing reduces that program to a. A survey of program slicing techniques tip researchindex abstract. Apr 29, 2016 refactoring is just a fancy way of describing a process in which you rewrite parts of your code to make them better. Code refactoring is the process of restructuring existing computer codechanging the factoringwithout changing its external behavior.
To learn more about refactoring, the natural starting point is my refactoring book, now in its second edition. Refactoring via program slicing and sliding ran ettinger programming tools group university of oxford in the advanced software tools research seminar. Program slicing proceedings of the 5th international. A direct application of program slicing in the field of refactoring is slice extraction, which has been formally defined by ettinger 2007 as the extraction of the computation of a set of variables v from a program s as a reusable program entity, and the update of the original program s to reuse the extracted slice. Program slicing, the study of meaningful subprograms that capture. Refactoring consists of improving the internal structure of an existing programs source code, while preserving its external behavior. Refactoring article about refactoring by the free dictionary. The goal of refactoring is to pay off technical debt. The vagaries of code inside these methods conceal the execution logic and make the method extremely hard to understand and even harder to change. We take it for granted that advanced refactoring tools will somehow need program slicing techniques, and therefore we shall design a novel variant of common slicing approaches to t refactoring s constraints. Using this technique, reading code to figure out what it does, to estimate the effort to modify it, etc. The task of computing program slices is called program slicing. Often, refactoring precedes a program modification or extension.
As a result many people now see code refactoring as an essential part of software development. If more programmers adopted refactoring tools, software projects could make enormous productivity gains. Improving the design of existing code 2nd edition addisonwesley signature series fowler see the best books of 2019. Refactoring via program slicing and sliding ran ettinger programming tools group university of oxford in the advanced software tools research seminar tel aviv university 30 october, 2006. Toolsupported refactoring of existing objectoriented code into aspects. Because a refactoring is intended to restructure a program without changing its behavior, a program should perform the same way after a refactoring as it does before.
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