[Haskell-cafe] Simple hash table creation

[Gregory Crosswhite]

Look in Data.Int for a list of the Int types.

Basically you generally only use Int unless you are working at a lower- 
level which has an explicit requirement for the number of bits.  In  
this case, HashTable has such a requirement, so you have two choices:   
you can either change the type annotation on dummy:


import Data.Int

dummy:: String -> Int32
dummy s = 7



or you can just leave it off entirely, and GHC will automatically  
infer the correct type (without you needing to import Data.Int):

dummy s = 7


On Nov 17, 2009, at 12:09 PM, michael rice wrote:

> Hi Daniel,
>
> Thanks for the IO monad reminder.
>
> What is GHC.Int.Int32? Can't find it on Hoogle.
>
> Michael
>
> ==================
>
> *Main> ht <- new (==) dummy :: IO MyHashTable
>
> <interactive>:1:15:
>     Couldn't match expected type `GHC.Int.Int32'
>            against inferred type `Int'
>     In the second argument of `new', namely `dummy'
>     In a stmt of a 'do' expression:
>         ht <- new (==) dummy :: IO MyHashTable
> *Main> :t dummy
> dummy :: String -> Int
> *Main>
>
>
>
> --- On Tue, 11/17/09, Daniel Fischer <daniel.is.fischer at web.de> wrote:
>
> From: Daniel Fischer <daniel.is.fischer at web.de>
> Subject: Re: [Haskell-cafe] Simple hash table creation
> To: haskell-cafe at haskell.org
> Date: Tuesday, November 17, 2009, 2:45 PM
>
> Am Dienstag 17 November 2009 20:36:46 schrieb Daniel Fischer:
> > What you probably wanted was
> >
> > type MyHashTable = HashTable String Int -- not data MyHashTable
> >
>
> Just in case it's not clear:
>
> > ht <- new (==) dummy :: IO MyHashTable
>
> only works at the prompt or in an IO do-block, not at the top level  
> of the module.
>
> >
> > then ht is a hashtable of type MyHashTable.
>
>
> _______________________________________________
> Haskell-Cafe mailing list
> Haskell-Cafe at haskell.org
> http://www.haskell.org/mailman/listinfo/haskell-cafe
>
> _______________________________________________
> Haskell-Cafe mailing list
> Haskell-Cafe at haskell.org
> http://www.haskell.org/mailman/listinfo/haskell-cafe

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.haskell.org/pipermail/haskell-cafe/attachments/20091117/3aead5d8/attachment.html