foldl' ?

Hal Daume III hdaume@ISI.EDU
Fri, 22 Nov 2002 13:44:06 -0800 (PST)


Because List is the H98 module, Data.List is the extended one which
contains foldl'.  Regardless of whether you say -package data or not,
you're not going to get Data.List unless you ask for it explicitly:

moussor:multidoc-sum/ ghci -package data
   ___         ___ _
  / _ \ /\  /\/ __(_)
 / /_\// /_/ / /  | |      GHC Interactive, version 5.04.1, for Haskell
98.
/ /_\\/ __  / /___| |      http://www.haskell.org/ghc/
\____/\/ /_/\____/|_|      Type :? for help.

Loading package base ... linking ... done.
Loading package haskell98 ... linking ... done.
Loading package lang ... linking ... done.
Loading package concurrent ... linking ... done.
Loading package posix ... linking ... done.
Loading package util ... linking ... done.
Loading package data ... linking ... done.
Prelude> :t List.foldl'

<interactive>:1: Variable not in scope: `List.foldl''
Prelude> :t Data.List.foldl'
forall a b. (a -> b -> a) -> a -> [b] -> a
Prelude> 


--
Hal Daume III

 "Computer science is no more about computers    | hdaume@isi.edu
  than astronomy is about telescopes." -Dijkstra | www.isi.edu/~hdaume

On Fri, 22 Nov 2002, Mark Carroll wrote:

> On Sat, 16 Nov 2002, Hal Daume III wrote:
> 
> > If it appears in Data.List then you need to import Data.List.  In order to
> > do this, you will need a newer (>=5.03) version of GHC, if I'm not
> > mistaken.
> 
> I find it curious that I can do:
> 
> cicero:markc$ ghci -package data
>    ___         ___ _
>   / _ \ /\  /\/ __(_)
>  / /_\// /_/ / /  | |      GHC Interactive, version 5.04, for Haskell 98.
> / /_\\/ __  / /___| |      http://www.haskell.org/ghc/
> \____/\/ /_/\____/|_|      Type :? for help.
> 
> Loading package base ... linking ... done.
> Loading package haskell98 ... linking ... done.
> Loading package lang ... linking ... done.
> Loading package concurrent ... linking ... done.
> Loading package posix ... linking ... done.
> Loading package util ... linking ... done.
> Loading package data ... linking ... done.
> Prelude> :type FiniteMap.lookupFM
> forall key elt.
> (Ord key) =>
> Data.FiniteMap.FiniteMap key elt -> key -> Maybe elt
> Prelude> :type List.isSuffixOf
> forall a. (Eq a) => [a] -> [a] -> Bool
> Prelude> :type List.foldl'
> 
> <interactive>:1: Variable not in scope: `List.foldl''
> Prelude>
> 
> 
> How come I can get at lookupFM and isSuffixOf but not foldl'? (-:
> 
> (Thanks to you and Richard for replies!)
> 
> -- Mark
> 
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