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Slim instance declaration

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(taken from a post to libraries mailing list)
 
(reference to Haskell-Cafe moved to "See also")
 
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This is an excerpt from "Disclipline for re-use: Slim instances"
 
http://www.haskell.org/pipermail/libraries/2006-September/005791.html
 
 
 
== All instance declarations should be slim. ==
 
== All instance declarations should be slim. ==
   
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and less re-invention of mostly trivial wheels.
 
and less re-invention of mostly trivial wheels.
   
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== See also ==
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* Haskell-Cafe: [http://www.haskell.org/pipermail/libraries/2006-September/005791.html Disclipline for re-use: Slim instances]
   
 
[[Category:Style]]
 
[[Category:Style]]

Latest revision as of 06:09, 5 September 2007

[edit] 1 All instance declarations should be slim.

This means

  • Instance declarations (and default definitions) should never contain non-trivial function definitions.
  • Instance declarations (and default definitions) should only provide "plumbing" to make existing functions accessible via the type class resolution mechanism.
  • The "plumbed" functions should always be exported (since instances are always exported).

Since the naming will not always be straight-forward, the last point is particularly important and would enable more re-use and less re-invention of mostly trivial wheels.


[edit] 2 See also