[vector] #54: Missing NFData instances for vector types

[vector]

#54: Missing NFData instances for vector types
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Reporter:  hvr          |        Owner:          
    Type:  enhancement  |       Status:  reopened
Priority:  blocker      |    Milestone:  0.10    
 Version:  0.7          |   Resolution:          
Keywords:               |  
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Comment(by basvandijk):

 Replying to [comment:22 rl]:
 > That's the question. Having the dependency (or a type function) probably
 makes more sense for things that actually live in monads. But as hvr
 points out, you might also want to have something like this:
 >
 > {{{
 > instance NFDataM [a] m
 > }}}

 Why should you want to do that? If you want to force immutable data use
 `rnf`, if you want to force mutable data in its associated monad use
 `rnfM`.

 > Then there is also the question of what to do with monad transformers.
 This seems like a not entirely trivial design question, perhaps it's worth
 discussing on the libraries list.

 Yes, I think that's a good idea.

 BTW my last example wasn't fully correct and general enough. It should be:

 {{{
 instance (NFData a, PrimMonad m, s ~ PrimState m) => NFDataM  (MVector s
 a) m where
   rnfM (MVector i n arr) = force i
         where
           force !ix | ix < n    = do x <- readArray arr ix
                                      rnf x `seq` force (ix+1)
                     | otherwise = return ()
 }}}

 (Note that this requires `UndecidableIntances`)

-- 
Ticket URL: <http://trac.haskell.org/vector/ticket/54#comment:23>
vector <http://trac.haskell.org/vector>
Package vector