Changes between Version 2 and Version 3 of OverlappingInstances


Ignore:
Timestamp:
Dec 5, 2005 4:11:36 AM (8 years ago)
Author:
john@…
Comment:

--

Legend:

Unmodified
Added
Removed
Modified
  • OverlappingInstances

    v2 v3  
    66== Brief Explanation == 
    77 
     8overlapping instances allow instances that can unify for the same class and will choose the most specific one available 
     9 
     10An alternate to what GHC implements would be to declare whether a class may be overlapping on a class by class basis. perhaps with something like 
     11{{{ 
     12class overlapping Foo a where 
     13   ... 
     14}}} 
     15 
    816== References == 
    917 * [http://www.haskell.org/ghc/docs/latest/html/users_guide/type-extensions.html#instance-overlap Section on overlapping instances] in the GHC User's Guide. 
    1018 
     19 
    1120== Pros == 
    12  * Pro 
    13  * Pro 
     21 * useful on occasion. 
     22 
    1423 
    1524== Cons == 
    16  * Con 
    17  * Con 
     25 * including a new module can silently change behavior of a program. 
     26 * makes it very easy for incorrect programs to still typecheck 
     27 * can cause confusing error messages 
     28 * can sometimes be simulated with the extra-method trick used in the Show class of the prelude for showing lists of characters differently than lists of other things.