Type error using Criterion - haskell

Question

I read the documentation and some articles that talk about the package, but I'm new to Haskell and did not understand much but I tried ....
Below is what I did:
module Main where
{-# LANGUAGE BangPatterns #-}
import Control.Parallel(par,pseq)
import Control.Exception
import Data.List
import IO
import Data.Char
import Criterion.Main (defaultMain, bench)
learquivo :: FilePath -> IO ([[Int]])
learquivo "mkList1.txt" = do
conteudo <- readFile "mkList1.txt"
return (read conteudo)
main = defaultMain [
bench "map sort learquivo" $ \n -> map sort learquivo
]
As it did the following error occurred:
Couldn't match expected type [[a]]
against inferred type FilePath -> IO [[Int]]

Answer 1

Just so you have how I usually run it, using the nf or whnf functions, I'll give my code:
import Data.List
import Criterion.Main
main :: IO ()
main = do
-- content <- learquivo "mkList1.txt"
let content = [ [big, big - step.. 0] | big <- [1000..1010], step <- [1..5]] :: [[Int]]
defaultMain
[ bench "benchmark-name" (nf (map sort) content)]
EDIT: If you like this then also give plotting a try:
module Main where
import Data.List
import Criterion.Main
import Criterion.Config
import Criterion.MultiMap as M
main :: IO ()
main = do
let myConfig = defaultConfig {
-- Always display an 800x600 window with curves.
cfgPlot = M.singleton KernelDensity (Window 800 600)
}
let content = [ [big, big-step.. 0] | big <- [1000..1010], step <- [1..5]] :: [[Int]]
defaultMainWith myConfig (return ())
[ bench "benchmark-name" (nf (map sort) content)]

Answer 2

The problem is this: map sort learquivo
sort expects a list, and so map sort expects a list of lists ([[a]]), whereas the type of learquivo is of type FilePath -> IO [[Int]].
You probably want something like:
main = do
contents <- learquivo "mkList1.txt"
defaultMain [
bench "map sort learquivo" $ \n -> map sort contents
]
There are various things in your code that could be cleaned up, but that should get you going.