[Haskell-beginners] reorganizing lists

[Bryce Verdier]

So I have a text full of x and y coordinates in the for x_y new line 
delimited. Here is the first 3 lines:
68_1
153_16099247764943158
153_775041589

I'm massaging the data to run a liner regression on it. At the moment 
the program I'm writing looks like this (still a work in progress...):

module Main where

import qualified Data.Text as T
import qualified Data.Text.IO as TI
import Numeric.GSL.Fitting.Linear
import Data.Packed.Vector

buildList :: IO [[T.Text]]
buildList = TI.readFile "lin_reg_data.txt" >>= return . map (T.split 
(=='_')) . T.lines

--main :: IO ()
--main = do
--    values <- buildList
--    let heads = fromList $ map (\x -> read (T.unpack . head $ x):: 
Double) values
--    let lasts = fromList $ map (\x -> read (T.unpack . last $ x):: 
Double) values
--    print linear heads lasts


I'm just trying to find a way to not iterate over "vaues" twice as that 
seems like a waste of computing time to me. Of course any advice on this 
would be appreciated.

Bryce


On 01/28/2013 10:42 AM, Ozgur Akgun wrote:
> Hi,
>
> On 28 January 2013 18:37, Bryce Verdier <bryceverdier at gmail.com 
> <mailto:bryceverdier at gmail.com>> wrote:
>
>     I know I can do this with calling 2 maps on the container, but I
>     would also like to do this in one iteration.
>
>
> As a learning experience, may I suggest you post the code you would 
> have written with two maps? Then we can try and improve on that to 
> have only one map.
>
> Best,
>
>
> -- 
> Ozgur Akgun
>
>
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