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principles:don_t_repeat_yourself

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principles:don_t_repeat_yourself [2020-10-12 14:02] – old revision restored (2012-12-18 15:19) 159.69.186.191principles:don_t_repeat_yourself [2021-09-02 11:47] – old revision restored (2021-05-11 19:02) 65.21.179.175
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 ===== Strategies ===== ===== Strategies =====
 +
 +  * Add a new invokable module (a function, a method, a class, etc.) instead of duplicating code
 +  * 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
 +
 +===== Caveats =====
 +
 +See section [[#contrary principles]].
  
  
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 ===== 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: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. + 
-/*[[wiki:Questioned]]*/+  * [[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. 
 + 
 +/*  * [[wiki:Questioned]]*/
  
  
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 ==== Generalizations ==== ==== Generalizations ====
  
 +  * [[Murphy's Law]] (ML):Duplication is a typical example for error possibilities. In case of a change, all instances of a duplicated piece of information have to be changed accordingly. So there is always the possibility to forget to change one of the duplicates. DRY is the application of ML to duplication.
  
 ==== Specializations ==== ==== Specializations ====
  
-  * [[principles:Generalization Principle]]: A generalized solution avoids duplication. +  * [[Once And Only Once]] (OAOO): This is the aspect of DRY which is concerned with the avoidance of (code) duplication. 
-  * [[principles:Once And Only Once]]: This is the aspect of DRY which is concerned with the avoidance of (code) duplication. +  * [[Single Choice Principle]] (SCP): Duplication can also be duplication of information about a set of possibilities. The SCP is about this aspect. 
-  * [[principles:Single Choice Principle]]: Duplication can also be duplication of information about a set of possibilities. The SCP is about this aspect. +  * [[Write Code That Writes Code]]: This is the code generation aspect of DRY.
-  * [[principles:Write Code That Writes Code]]: This is the code generation aspect of DRY.+
  
 ==== Contrary Principles ==== ==== Contrary Principles ====
  
-  * [[principles:Keep It Simple Stupid]]: Especially code generators can be very complex.+  * [[Keep It Simple Stupid]] (KISS): Especially code generators can be very complex.
  
 ==== Complementary Principles ==== ==== Complementary Principles ====
  
 +  * [[Generalization Principle]] (GP): A generalized solution avoids duplication.
  
 ==== Principle Collections ==== ==== Principle Collections ====
  
 {{page>collections:OOD Principle Language#Box}} {{page>collections:OOD Principle Language#Box}}
 +{{page>collections:Principles in "The Pragmatic Programmer"#Box}}
  
 ===== Example ===== ===== Example =====
principles/don_t_repeat_yourself.txt · Last modified: 2021-10-18 21:27 by christian