[Haskell-cafe] Lazy vs correct IO

Ketil Malde ketil at malde.org
Fri Sep 19 07:43:37 EDT 2008

oleg at okmij.org writes:

> It is interesting to compare the above main function with the
> corresponding lazy IO:

Minor point I know, but aren't you really comparing it with the
corresponding *strict* IO?

> main'' = do
>    names <- getArgs
>    files <- mapM readFile names

>    print $ length $ words (concat files)

This works nicely if you replace the middle line with a lazy version, e.g.:

   files <- mapM (unsafeInterleaveIO . B.readFile) names

If I haven't seen further, it is by standing in the footprints of giants

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