Re: [Haskell-beginners] Beginners Digest, Vol 89, Issue 38 How to define a simple function

24 Nov 2015

      On November 24, 2015 6:29:16 AM GMT+02:00, MJ Williams  wrote:
...
In short, your types do not match in your calculation of the half of
the length of the list.  According to GHCI
length :: [a] -> Int
(/) :: Fractional a => a -> a -> a
floor :: (Integral b, RealFrac a) => a -> b
Can you see how you might run into problems with this mixed bag of
types?
The only instance where you might find type compatibility between
above types would be if you were passing a value of type `Int' to a
function that accepted values of type `Integral'.  `Int', if you like,
is a subset of `Integral'
A simple solution would be to replace `/' with `div' (`div :: Integral
a => a -> a -> a').  Thus, your functionwould look something like
halve :: [a] -> [[a], [a]]
halve xs = [take longitud xs, drop longitud xs]
 where
 longitud = div (length xs) 2
Hope that helps, and don't hesitate to come back with more questions.
Matthew
On 23/11/2015, Francisco Gutierrez  wrote:
...
Dear sirs:I am defining a function halve, that breaks a list in two
halfs.
But I always get an error. Below is my code. What am I doing
wrong?Thanks!halve xs = [take (floor (longitud/2)), drop (floor
(longitud/2))]  where longitud = length xs
From: "beginners-request@haskell.org"

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 Sent: Saturday, November 21, 2015 8:21 PM
 Subject: Beginners Digest, Vol 89, Issue 38
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Today's Topics:
  1. Re:  Warning: Tab Character (Dan Stromberg)
  2. Re:  Warning: Tab Character (Jeon-Young Kang)
  3. Re:  Warning: Tab Character (Thomas Jakway)
----------------------------------------------------------------------
...
Message: 1
Date: Sat, 21 Nov 2015 16:44:21 -0800
From: Dan Stromberg 
To: The Haskell-Beginners Mailing List - Discussion of primarily
    beginner-level topics related to Haskell 
Subject: Re: [Haskell-beginners] Warning: Tab Character
Message-ID:

...
Content-Type: text/plain; charset="utf-8"
I believe the first version of make required tabs, but some
subsequent
versions have relaxed that requirement to make things easier.
Here's an example on a Linux Mint system (the 20's are of course
spaces) :
$ od -cx < Makefile
cmd output started 2015 Sat Nov 21 04:39:47 PM PST
0000000  \n  g  o  :  \n                  .  /  t  \n  \n
          670a    3a6f    200a    2020    2e20    742f    0a0a
0000016
above cmd output done    2015 Sat Nov 21 04:39:47 PM PST
dstromberg@dell-inspiron:/var/tmp/make-tabs i686-pc-linux-gnu 25234
$ make
cmd output started 2015 Sat Nov 21 04:39:48 PM PST
Makefile:3: *** missing separator.  Stop.
above cmd output done    2015 Sat Nov 21 04:39:48 PM PST
dstromberg@dell-inspiron:/var/tmp/make-tabs i686-pc-linux-gnu 25234
$ make --version
cmd output started 2015 Sat Nov 21 04:39:53 PM PST
GNU Make 3.81
Copyright (C) 2006  Free Software Foundation, Inc.
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE.
This program built for i686-pc-linux-gnu
above cmd output done    2015 Sat Nov 21 04:39:53 PM PST
dstromberg@dell-inspiron:/var/tmp/make-tabs i686-pc-linux-gnu 25234
I'll add that vim's Makefile syntax highlighting puts the
space-indented
line in red, suggesting an error.  Changing the spaces to a single
tab
makes the red go away.
HTH
On Sat, Nov 21, 2015 at 3:34 PM, Thomas Jakway 
wrote:
...
Why would make require tabs...?
Admittedly it's been a long time since I've written any makefiles by
hand
but I always use spaces instead of tabs and have never had any
...
...
On Nov 21, 2015 6:01 PM, David Moberg  wrote:
...
Have you found "soft tabs"? That option will make TextMate use
spaces
...
instead of tab characters. Read 4.11 "Using Spaces Instead of Tabs"
in
Dan
Strombergs link for instrucitons.
...
2015-11-21 21:36 GMT+01:00 Jeon-Young Kang :
...
I've tried to choose "instead of spaces". But there is no option
of
mine (Textmate 2 beta).
...
...
On Sat, Nov 21, 2015 at 3:14 PM, Dan Stromberg

wrote:
...
...
Perhaps enable soft tabs?
https://manual.macromates.com/en/working_with_text
This is an issue in Python too (at least from PEP8's

problems.
perspective) -
...
...
but note that many "make" programs require tabs instead of spaces.
...
...
...
On Sat, Nov 21, 2015 at 11:13 AM, Jeon-Young Kang

wrote:
...
>
> Hello everyone.
>
>
> I am a newbie of Haskell, using Textmate on mac.
>
>
> I got the following warning. How can I fix it?
>
>
> Warning:
>
>    Tab character
>
> Ok, modules loaded: Main.
>
>
>
> Sincerely,
> Young
>
> _______________________________________________
> Beginners mailing list
> Beginners@haskell.org
> http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
>
--
Dan Stromberg
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--
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Jeon-Young Kang
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Re: [Haskell-beginners] Beginners Digest, Vol 89, Issue 38 How to define a simple function

Gesh