[Haskell-cafe] (SPAM 3)Re: fmap use

[Tom Ellis]

If you want to print something out use putStrLn.  It will work.

On Fri, Dec 14, 2018 at 03:36:03PM +0100, Damien Mattei wrote:
> so itried you code,surpringly it compiles but when i launch it the
> function can not print somethin on screen, i assume it is because
> function are pure in haskell, nor with putStrln or Debug.trace:
> 
> getBD_WDS :: Connection -> String -> IO Float
> getBD_WDS conn name = do
>   let qry_head = "select DNUM from WDS where DISC = ?" :: Query
> 
>   bd_rows <- query conn qry_head (Only name)
> 
>   let lg = Prelude.length bd_rows
> 
> --  putStrLn (if lg > 1 then "some" else "one or zero")
>   let tst = trace (if lg > 1 then "some" else "one or zero") (if lg > 1
> then "some" else "one or zero")
> 
> --  let noBDtxt :: Text
>   let noBDtxt = fromOnly (Prelude.head bd_rows)
> 
>   --        noBDstr :: String
>   let noBDstr = Text.unpack noBDtxt
> 
> --        noBDfp :: Float
>   let noBDfp = read noBDstr
> 
>   return noBDfp