[Haskell-beginners] Strange behavior of program

[Carsten König]

No problem - Num can be a bit confusing at first - just make sure to
compare the right things ;)

Am 08.03.2015 um 15:08 schrieb m00nlight:
> Carsten and Arjanen,
>
> Thanks for your explanation.  :)
>
>
>
> --m00nlight
>
> 在2015年03月08 20时01分, "arjanen.loic"<arjanen.loic at gmail.com>写道:
>
>
>     Hello,
>
>     Given that you specifically indicated in your code that you
>     wanted Int’s instance of Read and that the result of the product
>     is way over 2 ^ 32 (or 2 ^ 64 for that matter), I’d guess the
>     difference comes from the fact that the product of a is done with
>     type Int (that is, modulo 32 or 64 depending on your computer’s
>     CPU architecture) and the product with the litteral list is done
>     with type Integer because that the type Haskell defaults to in
>     this case.
>
>     ARJANEN Loïc Jean David
>     http://blog.luigiscorner.com
>     ---
>     “Computer science is no more about computers than astronomy is
>     about telescopes, biology is about microscopes, or chemistry is
>     about beakers and test tubes. Science is not about tools. It is
>     about how we use them, and what we find out when we do.”
>     Michael R. Fellows and Ian Parberry
>
>     *De :* m00nlight <mailto:dot_wangyushi at yeah.net>
>     *Envoyé :* ‎dimanche‎ ‎8‎ ‎mars‎ ‎2015 ‎21‎:‎59
>     *À :* The Haskell-Beginners Mailing List - Discussion of primarily
>     beginner-level topics related to Haskell
>     <mailto:beginners at haskell.org>
>
>         
>     Hi Haskellers,
>
>     I encounter an strange behavior of haskell program recently.  The
>     following is my program
>
>     ```haskell
>     main = do
>         _ <- getLine
>         arr1 <- getLine
>         _ <- getLine
>        arr2 <- getLine
>        let a = map (read :: String -> Int) (words arr1)
>             b = map (read :: String -> Int) (words arr2)
>
>       putStrLn $ show $ (foldl (*) 1 a)
>       putStrLn $ show $ a ==
>     [1,2,4,8,32,64,128,256,512,1024,2048,4906,8192]
>       putStrLn $ show $ (foldl (*) 1
>     [1,2,4,8,32,64,128,256,512,1024,2048,4906,8192])
>     ```
>
>     With the input test file as following:
>
>     ```test.in
>     13
>     1 2 4 8 32 64 128 256 512 1024 2048 4906 8192
>     9
>     1 3 9 27 81 243 729 2187 6561
>     ```
>
>     The output is as:
>     ```output
>     0
>     True
>     185343439719667835347140608
>     ```
>
>     In fact, from the program, we know that a is equal to list 
>     [1,2,4,8,32,64,128,256,512,1024,2048,4906,8192] ,
>     but the product of a and the literal list is different.
>
>     Can anyone tell me why?
>
>     Thanks       
>
>
>
>
>     --m00nlight
>
>
>
>
>
>
>
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