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principles:don_t_repeat_yourself [2013-04-03 13:33]
christian [Evidence]
principles:don_t_repeat_yourself [2015-06-26 15:45] (current)
207.107.205.22 [Strategies]
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   * [[contexts:​Object-Oriented Design]]   * [[contexts:​Object-Oriented Design]]
 +  * [[contexts:​Implementation]]
 ===== Principle Statement ===== ===== Principle Statement =====
  
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   * Add a new invokable module (a function, a method, a class, etc.) instead of duplicating code   * Add a new invokable module (a function, a method, a class, etc.) instead of duplicating code
 +  * Factor out a common base class
   * Use code generation when information has to be represented in multiple forms   * Use code generation when information has to be represented in multiple forms
   * Use polymorphism to avoid repeatedly enumerating a set of possible solutions in if or switch statements   * Use polymorphism to avoid repeatedly enumerating a set of possible solutions in if or switch statements
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 ===== Origin ===== ===== Origin =====
  
-Andrew Hunt and David Thomas//​[[http://​pragprog.com/​book/​tpp/​the-pragmatic-programmer|The Pragmatic Programmer: From Journeyman to Master]]//​ +{{page>​resources:The Pragmatic Programmer#​reference}}
- +
 ===== Evidence ===== ===== Evidence =====
 /* Comment out what is not applicable and explain the rest: */ /* Comment out what is not applicable and explain the rest: */
 /*  * [[wiki:​Proposed]]*/​ /*  * [[wiki:​Proposed]]*/​
-/*  * [[wiki:​Examined]]*/​ 
  
-  * [[wiki:​Accepted]]:​ It is generally agreed upon that code duplication is to be avoided. On the other hand the broader meaning of DRY which results in the heavy use of code generators is often not considered. On the other hand ''​The Pragmatic Programmer'' ​is a well known book which makes DRY a well-known and accepted principle.+  ​* [[wiki:​Examined]]:​ There is extensive research on code cloning, its reasons, automatic detection of code clones, their evolution, etc. In ((Chanchal Kumar Roy and James R. Cordy: //​[[http://​citeseerx.ist.psu.edu/​viewdoc/​summary;​jsessionid=EBC3E3E783AE0B5DEF75B9EDD4F1C9E2?​doi=10.1.1.62.7869|A survey on software clone detection research]]//​)) Chanchal Kumar Roy and James R. Cordy present a 115 page survey on the state of research as of 2007. Many unanswered questions remain and research is still ongoing. In 2009 Juergens et al. ((Elmar Juergens, Florian Deissenboeck,​ Benjamin Hummel, and Stefan Wagner //​[[http://​www4.in.tum.de/​~deissenb/​publications/​2009_juergens_inconsistens_clones.pdf|Do code clones matter?​]]//​)) analyzed fife systems written in C#, Cobol and Java each between around 200 and 500 kLOC. They identified clones and intentionally and unintentionally inconsistent changes to them. They then related the faulty clones to them and came to the expected conclusion that clones are changed inconsistently and that this results in faults. So at least the part of DRY about code duplication is supported by research findings. 
 +  ​* [[wiki:​Accepted]]:​ It is generally agreed upon that code duplication is to be avoided. On the other hand the broader meaning of DRY which results in the heavy use of code generators is often not considered. On the other hand //The Pragmatic Programmer// is a well known book which makes DRY a well-known and accepted principle.
  
 /*  * [[wiki:​Questioned]]*/​ /*  * [[wiki:​Questioned]]*/​
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 ===== Description Status ===== ===== Description Status =====
 /* Choose one of the following and comment out the rest: */ /* Choose one of the following and comment out the rest: */
-[[wiki:​Stub]] +/*[[wiki:​Stub]]*
-/*[[wiki:​Incomplete]]*/+[[wiki:​Incomplete]]
 /​*[[wiki:​Complete]]*/​ /​*[[wiki:​Complete]]*/​
  
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   * [[http://​programmer.97things.oreilly.com/​wiki/​index.php/​Don'​t_Repeat_Yourself|97things:​ Don'​t_Repeat_Yourself]]   * [[http://​programmer.97things.oreilly.com/​wiki/​index.php/​Don'​t_Repeat_Yourself|97things:​ Don'​t_Repeat_Yourself]]
  
 +===== Discussion =====
 +
 +Discuss this wiki article and the principle on the corresponding [[talk:​principles:​Don'​t Repeat Yourself|talk page]].
principles/don_t_repeat_yourself.1364988816.txt.gz · Last modified: 2013-05-20 12:46 (external edit)