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Today's Topics:
1. Passing a file containing a list as an input (Awsaf Rahman)
2. Re: Passing a file containing a list as an input (Tobias Brandt)
3. Execution time of Mergesort (Awsaf Rahman)
4. Re: Execution time of Mergesort (KC)
5. Re: Execution time of Mergesort (Awsaf Rahman)
----------------------------------------------------------------------
Message: 1
Date: Thu, 5 Jul 2018 22:21:15 +0200
From: Awsaf Rahman <[email protected]>
To: [email protected]
Subject: [Haskell-beginners] Passing a file containing a list as an
input
Message-ID:
<caoh+qtdwoi6sypgp1+6gticin1rfqozmzjr33anrtomctgk...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
Hello everyone!
I am really struggling with Haskell I/O.
I have written a mergesort program and as an input to that program I want
to use a file containing a list of 1000 integers. Let's say the contents of
the file look like this
[120, 400, 500 , 20, 100 ..]
How can I achieve that? I am trying to write a main function that takes the
file as an input and passes the list to my mergesort function..
Regards
Awsaf Rahman
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Message: 2
Date: Thu, 05 Jul 2018 22:36:39 +0200
From: Tobias Brandt <[email protected]>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <[email protected]>
Subject: Re: [Haskell-beginners] Passing a file containing a list as
an input
Message-ID:
<20180705223639.horde.xya17xzozlb2efl2sr-t...@webmail.uni-bremen.de>
Content-Type: text/plain; charset="utf-8"; Format="flowed";
DelSp="Yes"
Hello Awsaf,
you should probably look further into the topic of "IO in Haskell" and
"Monads". Then you can use impure functions like readFile
(http://hackage.haskell.org/package/base-4.11.1.0/docs/Prelude.html#v:readFile
) or getArgs
(http://hackage.haskell.org/package/base-4.11.1.0/docs/System-Environment.html#v:getArgs).
A naive solution might look like
this:
module Main where
import System.Environment (getArgs)
main = do
(fileName:_) <- getArgs
unsortedList <- read <$> readFile fileName
let sorted = yourMergeSortFunction unsortedList
print sorted -- maybe you like to print your sorted list
Best regards,
Tobias
----- Nachricht von Awsaf Rahman <[email protected]> ---------
Datum: Thu, 5 Jul 2018 22:21:15 +0200
Von: Awsaf Rahman <[email protected]>
Antwort an: The Haskell-Beginners Mailing List - Discussion of
primarily beginner-level topics related to Haskell
<[email protected]>
Betreff: [Haskell-beginners] Passing a file containing a list as an input
An: [email protected]
> Hello everyone!
> I am really struggling with Haskell I/O.
>
> I have written a mergesort program and as an input to that
> program I want to use a file containing a list of 1000 integers.
> Let's say the contents of the file look like this
>
> [120, 400, 500 , 20, 100 ..]
>
> How can I achieve that? I am trying to write a main function that
> takes the file as an input and passes the list to my mergesort
> function..
>
> Regards
> Awsaf Rahman
----- Ende der Nachricht von Awsaf Rahman <[email protected]> -----
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Message: 3
Date: Fri, 6 Jul 2018 04:01:27 +0200
From: Awsaf Rahman <[email protected]>
To: [email protected]
Subject: [Haskell-beginners] Execution time of Mergesort
Message-ID:
<caoh+qte-_1vidhqutjtf83ip8opgdwxlmnm3r+parb8mmf4...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
Hello everyone!
I am trying to find out the execution time of mergesort for a list size of
1 million integers. I have done the same in Erlang as well and the
execution time in Erlang was around 0.93 seconds. I have implemented the
program in almost the same way in Haskell as well but for some reason the
Haskell implementation is taking around 12 seconds which doesn't seem
right.
Here is the implementation in Haskell:
*{-# 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 ++ "]")*
*main = do*
* file <- getLine*
* contents <- readFile file*
* let !unsortedlist = (toList contents)*
* start <- getTime Monotonic*
* evaluate(force (mergesort unsortedlist))*
* end <- getTime Monotonic*
* fprint (timeSpecs % "\n") start end*
What am I doing wrong?
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Message: 4
Date: Thu, 5 Jul 2018 19:06:10 -0700
From: KC <[email protected]>
To: Haskell Beginners <[email protected]>
Subject: Re: [Haskell-beginners] Execution time of Mergesort
Message-ID:
<CAMLKXyk49OkO47JF1Yys0TL=wz-1cizbsqw7--hg89qjooa...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
I haven't looked at the code much yet
But might want to consider strictness 😎
--
Sent from an expensive device which will be obsolete in a few months
Casey
On Thu, Jul 5, 2018, 7:01 PM Awsaf Rahman, <[email protected]>
wrote:
> Hello everyone!
>
> I am trying to find out the execution time of mergesort for a list size of
> 1 million integers. I have done the same in Erlang as well and the
> execution time in Erlang was around 0.93 seconds. I have implemented the
> program in almost the same way in Haskell as well but for some reason the
> Haskell implementation is taking around 12 seconds which doesn't seem
> right.
>
> Here is the implementation in Haskell:
>
> *{-# 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 ++ "]")*
>
> *main = do*
> * file <- getLine*
> * contents <- readFile file*
> * let !unsortedlist = (toList contents)*
> * start <- getTime Monotonic*
> * evaluate(force (mergesort unsortedlist))*
> * end <- getTime Monotonic*
> * fprint (timeSpecs % "\n") start end*
>
>
> What am I doing wrong?
> _______________________________________________
> Beginners mailing list
> [email protected]
> http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
>
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Message: 5
Date: Fri, 6 Jul 2018 04:14:37 +0200
From: Awsaf Rahman <[email protected]>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <[email protected]>
Subject: Re: [Haskell-beginners] Execution time of Mergesort
Message-ID:
<caoh+qtevzwb7_-nef4gkt3wfzrzkdmwc4pyrty+rnyesnua...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
I did consider strictness and that is why the execution time has come down
from 16 seconds to 12 seconds! But I can't seem to find the issue anymore!
On Fri, Jul 6, 2018 at 4:06 AM, KC <[email protected]> wrote:
> I haven't looked at the code much yet
> But might want to consider strictness 😎
>
> --
> Sent from an expensive device which will be obsolete in a few months
> Casey
>
> On Thu, Jul 5, 2018, 7:01 PM Awsaf Rahman, <[email protected]>
> wrote:
>
>> Hello everyone!
>>
>> I am trying to find out the execution time of mergesort for a list size
>> of 1 million integers. I have done the same in Erlang as well and the
>> execution time in Erlang was around 0.93 seconds. I have implemented the
>> program in almost the same way in Haskell as well but for some reason the
>> Haskell implementation is taking around 12 seconds which doesn't seem
>> right.
>>
>> Here is the implementation in Haskell:
>>
>> *{-# 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 ++ "]")*
>>
>> *main = do*
>> * file <- getLine*
>> * contents <- readFile file*
>> * let !unsortedlist = (toList contents)*
>> * start <- getTime Monotonic*
>> * evaluate(force (mergesort unsortedlist))*
>> * end <- getTime Monotonic*
>> * fprint (timeSpecs % "\n") start end*
>>
>>
>> What am I doing wrong?
>> _______________________________________________
>> Beginners mailing list
>> [email protected]
>> http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
>>
>
> _______________________________________________
> Beginners mailing list
> [email protected]
> http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
>
>
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