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No problem - Num can be a bit confusing at first - just make sure to
compare the right things ;)<br>
<br>
<div class="moz-cite-prefix">Am 08.03.2015 um 15:08 schrieb
m00nlight:<br>
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cite="mid:eda9ce5.34b.14bf9b76107.Coremail.dot_wangyushi@yeah.net"
type="cite">
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<div><span style="max-width: 122px;" class="txt js-text
f-size-huge">Carsten and Arjanen,<br>
<br>
Thanks for your explanation. :)<br>
</span></div>
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<div><br>
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<div>--m00nlight<br>
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<div>在2015年03月08 20时01分,
"arjanen.loic"<a class="moz-txt-link-rfc2396E" href="mailto:arjanen.loic@gmail.com"><arjanen.loic@gmail.com></a>写道:</div>
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<div>Hello,</div>
<div><br>
</div>
<div>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.<br>
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<div>ARJANEN Loïc Jean David<br>
<a class="moz-txt-link-freetext" href="http://blog.luigiscorner.com">http://blog.luigiscorner.com</a><br>
--- <br>
“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.”<br>
Michael R. Fellows and Ian Parberry</div>
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229); border-top-width: 1px; border-top-style: solid;">
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face="'Calibri', 'Segoe UI', 'Meiryo', 'Microsoft YaHei
UI', 'Microsoft JhengHei UI', 'Malgun Gothic',
'sans-serif'"><b>De :</b> <a moz-do-not-send="true"
href="mailto:dot_wangyushi@yeah.net" target="_parent">m00nlight</a><br>
<b>Envoyé :</b> dimanche 8 mars 2015 21:59<br>
<b>À :</b> <a moz-do-not-send="true"
href="mailto:beginners@haskell.org" target="_parent">The
Haskell-Beginners Mailing List - Discussion of
primarily beginner-level topics related to Haskell</a></font></div>
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<div dir="">
<div style="color: rgb(0, 0, 0); font-family: arial;
font-size: 14px;">
<div>Hi Haskellers,<br>
<br>
I encounter an strange behavior of haskell program
recently. The following is my program<br>
<br>
```haskell<br>
main = do<br>
_ <- getLine<br>
arr1 <- getLine<br>
_ <- getLine<br>
arr2 <- getLine<br>
let a = map (read :: String -> Int) (words arr1)<br>
b = map (read :: String -> Int) (words arr2)<br>
<br>
putStrLn $ show $ (foldl (*) 1 a)<br>
putStrLn $ show $ a ==
[1,2,4,8,32,64,128,256,512,1024,2048,4906,8192]<br>
putStrLn $ show $ (foldl (*) 1
[1,2,4,8,32,64,128,256,512,1024,2048,4906,8192])<br>
```<br>
<br>
With the input test file as following:<br>
<br>
```test.in<br>
13<br>
1 2 4 8 32 64 128 256 512 1024 2048 4906 8192<br>
9<br>
1 3 9 27 81 243 729 2187 6561<br>
```<br>
<br>
The output is as:<br>
```output<br>
0<br>
True<br>
185343439719667835347140608<br>
```<br>
<br>
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] ,<br>
but the product of a and the literal list is different.<br>
<br>
Can anyone tell me why?<br>
<br>
Thanks <br>
<br>
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<div>
<div>--m00nlight<br>
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<br>
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