[Haskell-cafe] Re: semi-closed handles

[ChrisK]

Ryan Ingram wrote:
> I usually use something like this instead:
> 
> hStrictGetContents :: Handle -> IO String
> hStrictGetContents h = do
>     s <- hGetContents h
>     length s `seq` hClose h
>     return s

A small idiomatic nitpick:  When I see (length s) gets computed and thrown away 
I wince at the wasted effort.  I would prefer (finiteSpine s):

finiteSpine = foldr (const id) ()

hStrictGetContents :: Handle -> IO String
hStrictGetContents h = do
     s <- hGetContents h
     finiteSpine s `seq` hClose h
     return s

"finiteSpine" finds the "end" of a finite list and will hang forever on an 
infinite list.  One can even notice that the type of finiteSpine is Strategy [a]:

import Control.Parallel.Strategies(Strategy)
finiteSpine :: Strategy [a]
finiteSpine = foldr (const id) ()

And in fact "finiteSpine = seqList r0", which returns () after applying the "do 
nothing" strategy "r0" to every element.

-- 
Chris