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Today's Topics:
1. Re: where do i get wrong (Ryan Stradling)
2. Re: where do i get wrong (Roelof Wobben)
3. Re: where do i get wrong (Emanuel Koczwara)
----------------------------------------------------------------------
Message: 1
Date: Sun, 2 Mar 2014 14:44:41 -0500
From: Ryan Stradling <[email protected]>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <[email protected]>
Subject: Re: [Haskell-beginners] where do i get wrong
Message-ID:
<CAFVzk8VNZd631A_yOxeHM=6qsg4vc8byyfo8bxmdkuwygef...@mail.gmail.com>
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isLower takes a character. You need to look at operating on the string
with higher order functions which will call isLower on each character.
On Mar 2, 2014 2:25 PM, "Roelof Wobben" <[email protected]> wrote:
> Found this one:
>
> This is partly working:
>
> import Data.Char
>
> x = "aBCde".isLower
> -- Note that comments are preceded by two hyphens
> {- or enclosed
> in curly brace/hypens pairs. -}
> main = print x
>
>
> But now I see this error:
>
> - Main.hs@3:5-3:12
> Couldn't match expected type `b0 -> c0' with actual type `[Char]' In
> the first argument of `(.)', namely `"aBCde"' In the expression: "aBCde" .
> isLower In an equation for `x': x = "aBCde" . isLower
> - In an equation for `x': x = "aBCde" . isLower
>
>
> Roelof
>
> Roelof Wobben schreef op 2-3-2014 20:10:
>
> Thanks,
>
> isLower is in base package.
> The tutorial has not spoken about importing modules.
>
> I use the IDE of fpcomplete.
>
> Roelof
>
>
>
> Bob Ippolito schreef op 2-3-2014 20:02:
>
> isLower is not in the Prelude (the automatically imported module built-in
> functions). Here's the list of all functions in Prelude:
> http://hackage.haskell.org/package/base/docs/Prelude.html
>
> isLower is in another module. You can figure that out by searching for
> "isLower" on Hoogle:
> http://www.haskell.org/hoogle/
>
> You can even find it by searching for it by type, which is useful if you
> don't remember the precise name. Try searching for "Char -> Bool".
>
> In other words, you'll need to import isLower from somewhere before you
> can use it.
>
>
>
> On Sun, Mar 2, 2014 at 10:45 AM, Roelof Wobben <[email protected]> wrote:
>
>> Hello,
>>
>> I try to selfstudy haskell by following the yet another haskell tutorial.
>>
>> Now I have the exercise where I have a string and have to convert it into
>> a list of Booleans based on lower cats letter using map.
>>
>> So i tried this
>>
>> x = "aBCde".islower:[]
>>
>> But I see this error : Not in Scope: 'isLower'.
>>
>> Where do I make my error.
>>
>> Do not give the answer otherwise I do not learn anything from it.
>>
>> Roelof
>>
>>
>> ---
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>
>
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Message: 2
Date: Sun, 02 Mar 2014 20:50:09 +0100
From: Roelof Wobben <[email protected]>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <[email protected]>
Subject: Re: [Haskell-beginners] where do i get wrong
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Message: 3
Date: Sun, 02 Mar 2014 20:54:13 +0100
From: Emanuel Koczwara <[email protected]>
To: [email protected]
Subject: Re: [Haskell-beginners] where do i get wrong
Message-ID: <[email protected]>
Content-Type: text/plain; charset="iso-8859-1"; Format="flowed"
Hi,
W dniu 02.03.2014 20:24, Roelof Wobben pisze:
> Found this one:
>
> This is partly working:
>
> import Data.Char
>
> x = "aBCde".isLower
> -- Note that comments are preceded by two hyphens
> {- or enclosed
> in curly brace/hypens pairs. -}
> main = print x
>
>
> But now I see this error:
>
> *
> Main.hs@3:5-3:12
> Couldn't match expected type `b0 -> c0' with actual type `[Char]'
> In the first argument of `(.)', namely `"aBCde"' In the
> expression: "aBCde" . isLower In an equation for `x': x = "aBCde"
> . isLower
> *
> In an equation for `x': x = "aBCde" . isLower
>
>
> Roelof
This expression is wrong:
"aBCde".isLower
You call (.) function with 2 arguments: "aBCde" and isLower. This
doesn't make sense for the compiler (type checker).
Regards,
Emanuel
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