On Friday 10 June 2011, 13:49:23, Dmitri O.Kondratiev wrote:
> On Thu, Jun 9, 2011 at 11:31 AM, Max Bolingbroke
> <[email protected]
>
> > wrote:
> >
> > If you want plain text serialization, "writeFile "output.txt" . show"
> > and "fmap read (readFile "output.txt")" should suffice...
> >
> > Max
>
> This code works:
>
> main = do
> let xss = [[1,2,3],[4,5,6],[7,8],[9]]
> writeFile "output.txt" (show xss)
> line <- readFile "output.txt"
> let xss2 = read line :: [[Int]]
> print xss2
>
> As soon as complete file is returned as a single line, using 'fmap'
> does not make sense here:
> line <- readFile "output.txt"
> let xss2 = fmap read line
>
> When to use 'fmap'?
xss2 <- fmap read (readFile "output.txt")
or
xss2 <- read `fmap` readFile "output.txt"
But it might be necessary to tell the compiler which type xss2 ought to
have, so it knows which `read' to invoke, if it can't infer that from later
use.
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