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Today's Topics:
1. Re: another type problem
(Sumit Sahrawat, Maths & Computing, IIT (BHU))
2. Re: another type problem (Brandon Allbery)
3. Re: another type problem
(Sumit Sahrawat, Maths & Computing, IIT (BHU))
4. Re: another type problem (Roelof Wobben)
----------------------------------------------------------------------
Message: 1
Date: Tue, 12 May 2015 19:54:54 +0530
From: "Sumit Sahrawat, Maths & Computing, IIT (BHU)"
<[email protected]>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <[email protected]>
Subject: Re: [Haskell-beginners] another type problem
Message-ID:
<CAJbEW8OF+7=2snvphquxgio9ltcsypx-nslf4r6+nbkjrcb...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
The type of the cons operator (:) is
(:) :: a -> [a] -> [a]
The way you are invoking it expects it to have the type
(:) :: a -> Maybe [a] -> [a] -- not valid
One solution is to write such a function yourself, while the other would be
to rewrite your code to invoke it correctly.
On 12 May 2015 at 19:46, Brandon Allbery <[email protected]> wrote:
> On Tue, May 12, 2015 at 10:11 AM, Roelof Wobben <[email protected]> wrote:
>
>> I do not understand what you are saying to me.
>>
>> I know that init produces a Maybe [a] . That is why I did put a Just
>> before it.
>>
>
> You are invoking it again though, and using its result as if it produces
> [a] instead of Maybe [a].
>
> --
> brandon s allbery kf8nh sine nomine
> associates
> [email protected]
> [email protected]
> unix, openafs, kerberos, infrastructure, xmonad
> http://sinenomine.net
>
> _______________________________________________
> Beginners mailing list
> [email protected]
> http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
>
>
--
Regards
Sumit Sahrawat
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Message: 2
Date: Tue, 12 May 2015 10:25:04 -0400
From: Brandon Allbery <[email protected]>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <[email protected]>
Subject: Re: [Haskell-beginners] another type problem
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On Tue, May 12, 2015 at 10:21 AM, Roelof Wobben <[email protected]> wrote:
> What is then the right way to do. I still do not understand what you are
> trying to make clear to me.
>
Ask yourself: what is the type of (Just (x: (init' xs))) ?
--
brandon s allbery kf8nh sine nomine associates
[email protected] [email protected]
unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net
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Message: 3
Date: Tue, 12 May 2015 19:56:20 +0530
From: "Sumit Sahrawat, Maths & Computing, IIT (BHU)"
<[email protected]>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <[email protected]>
Subject: Re: [Haskell-beginners] another type problem
Message-ID:
<CAJbEW8O=pEHVLJ23jN=jcHtVg=sdaie+jwtwwvsxp2lyk8a...@mail.gmail.com>
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Also remember that Just has the type
Just :: a -> Maybe a
Thus putting in a Just doesn't help with your issue.
On 12 May 2015 at 19:54, Sumit Sahrawat, Maths & Computing, IIT (BHU) <
[email protected]> wrote:
> The type of the cons operator (:) is
>
> (:) :: a -> [a] -> [a]
>
> The way you are invoking it expects it to have the type
>
> (:) :: a -> Maybe [a] -> [a] -- not valid
>
> One solution is to write such a function yourself, while the other would
> be to rewrite your code to invoke it correctly.
>
> On 12 May 2015 at 19:46, Brandon Allbery <[email protected]> wrote:
>
>> On Tue, May 12, 2015 at 10:11 AM, Roelof Wobben <[email protected]> wrote:
>>
>>> I do not understand what you are saying to me.
>>>
>>> I know that init produces a Maybe [a] . That is why I did put a Just
>>> before it.
>>>
>>
>> You are invoking it again though, and using its result as if it produces
>> [a] instead of Maybe [a].
>>
>> --
>> brandon s allbery kf8nh sine nomine
>> associates
>> [email protected]
>> [email protected]
>> unix, openafs, kerberos, infrastructure, xmonad
>> http://sinenomine.net
>>
>> _______________________________________________
>> Beginners mailing list
>> [email protected]
>> http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
>>
>>
>
>
> --
> Regards
>
> Sumit Sahrawat
>
--
Regards
Sumit Sahrawat
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Message: 4
Date: Tue, 12 May 2015 16:27:30 +0200
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] another type problem
Message-ID: <[email protected]>
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