[Haskell-cafe] Why Haskell?

[Simon Peyton-Jones]

Looks possible.  But it'd depend on using '>>' not '>>= \_ -> ...', so a
bit fragile.  

Simon

| -----Original Message-----
| From: haskell-cafe-bounces at haskell.org
[mailto:haskell-cafe-bounces at haskell.org] On Behalf Of Neil
| Mitchell
| Sent: 23 July 2006 13:57
| To: Bulat Ziganshin
| Cc: haskell-cafe at haskell.org
| Subject: Re: Re[2]: [Haskell-cafe] Why Haskell?
| 
| Hi,
| 
| > sequence [] = return []
| > sequence (action:actions) = do x <- action
| >                                xs <- sequence actions
| >                                return (x:xs)
| >
| > sequence_ [] = return ()
| > sequence_ (action:actions) = do action
| >                                 sequence_ actions
| 
| So, by appending an underscore at the end of a name, you massively
| improve the runtime behaviour of the program. That to me sounds like a
| hack :)
| 
| Would it not be possible to add a GHC rule like the following:
| 
| forall a b . sequence a >> b  = sequence_ a >> b
| 
| I'm not sure if thats correct, a valid rule definition, or semantics
| preserving, but if it was it would be nice :)
| 
| Thanks
| 
| Neil
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