toList :: String -> [Integer]
toList input = read ("[" ++ input ++ "]")

That was creative, but a more idiomatic way to write that would be to use the split package

stack ghci --package split

import Data.Split

toList :: String -> [Integer]
toList = fmap read . splitOn ","

As for how to aggregate times, start thinking about the types before you start.  Each iteration you should take a List and return a TimeSpec.

testcase :: [Integer] -> IO TimeSpec
testcase l = do
  start <- getTime Monotonic
  evaluate (mergesort l)
  end <- getTime Monotonic
  return $ diffTimeSpec start end

Now, we need to run it 100 times and collect the times.  Sounds like a job for map, but since testcase is monadic, use mapM instead (or traverse).

main = do
  unsortedList <- undefined
  times <- mapM (\c -> testcase unsortedList) [1..100]
  print times

On Mon, Jul 9, 2018 at 9:40 AM, Awsaf Rahman <awsafrahman1704@gmail.com> wrote:
Okay, here is what I am trying to do. I am trying to time this mergesort program. I want to run this program 100, 1000, etc times and store the timing results in a list if possible. Can't seem to figure out how to do it! The following program prints the timings to the shell and I need to figure out a way to store the timings in a list.


{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE BangPatterns #-}
import Control.Exception
import Formatting
import Formatting.Clock
import System.Clock
import Control.DeepSeq

mergesort [] = []
mergesort [x] = [x]
mergesort xs = let (lhalf, rhalf) = splitAt (length xs `div` 2) xs
               in merge' (mergesort lhalf) (mergesort rhalf)

merge' lhalf rhalf = merge lhalf rhalf []

merge [] [] acc = reverse acc
merge [] y acc = reverse acc ++ y
merge x [] acc = reverse acc ++ x

merge (l:ls) (r:rs) acc
        | l < r = merge ls (r:rs) (l:acc)
        | otherwise = merge rs (l:ls) (r:acc)

toList :: String -> [Integer]
toList input = read ("[" ++ input ++ "]")

repeater unsortedlist 0 result = return (result)

repeater unsortedlist counter result = do
                            start <- getTime Monotonic
                            evaluate(mergesort unsortedlist)
                            end <- getTime Monotonic
                            fprint (timeSpecs % "\n") start end
                            repeater unsortedlist (counter-1) result

main = do
    file <- getLine
    contents <- readFile file
    let !unsortedlist = (toList contents)
    repeater unsortedlist 100 []


On Mon, Jul 9, 2018 at 3:21 PM, David McBride <toad3k@gmail.com> wrote:
I guess whatever version you are using did not export that function.  In any case the definition for that function is incredibly simple, so you could just write your own for now.

diffTimeSpec :: TimeSpec -> TimeSpec -> TimeSpec
diffTimeSpec ts1 ts2 = abs (ts1 - ts2)


On Mon, Jul 9, 2018 at 9:08 AM, Awsaf Rahman <awsafrahman1704@gmail.com> wrote:
I imported the System.Clock module and tried to use the diffTimeSpec function but it keeps saying "out of scope". 

On Mon, Jul 9, 2018 at 2:45 PM, David McBride <toad3k@gmail.com> wrote:
There is a diffTimeSpec function in that module that seems like it would work.

On Mon, Jul 9, 2018 at 8:30 AM, Awsaf Rahman <awsafrahman1704@gmail.com> wrote:
Hello, 

I am trying to time a function I have written in haskell using the clock package in the following way: 

start <- getTime Monotonic
evaluate(something)
end <- getTime Monotonic
fprint (timeSpecs % "\n") start end


Now what I want is to store the time difference between start and end. Is there a way I can do that? 

Regards 
Awsaf

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