What is this error?
===

What is this error?

1.hs:41:30:
    Couldn't match expected type `Eval [a]' against inferred type `()'



`module Main where   
 
import Control.Parallel(par,pseq)   
import Text.Printf   
import Control.Exception   
import System.CPUTime   
import Data.List   
import IO   
import Data.Char   
import Control.DeepSeq  
import Control.Parallel.Strategies 
 
--Calcula o tempo entre o inicio e o fim de rodagem do programa   
time :: IO t -> IO t   
time a = do   
    start <- getCPUTime   
    v <- a 
    end   <- getCPUTime   
    let diff = (fromIntegral (end - start)) / (10^12)   
    printf "Computation time: %0.3f sec\n" (diff :: Double)   
    return v   
 
learquivo :: FilePath -> IO ([[Int]])   
learquivo s = do    
            conteudo <- readFile s    
            return (read conteudo)    
 
main :: IO ()   
main = do    
    t1 <- getCPUTime  
    conteudo <- learquivo "list.txt"  
    let !mapasort = (map qsort conteudo) `using` (parList rdeepseq)  
    t2 <- getCPUTime  
    let difft2t1 = (fromIntegral (t2 -t1)) / (10^12)  
    printf "Computation time %0.3f sec" (difft2t1 :: Double)  

qsort [] = []  
qsort [x] = [x]  
qsort (x:xs) =  
	losort ++ (x:hisort) `using` strategy  
	where  
		losort = qsort [y|y <- xs, y < x]  
		hisort = qsort [y|y <- xs, y >= x]  
		strategy result = rnf losort `par`  
					rnf hisort `pseq`  
					rnf result `

    
Thanks

 