[Haskell-beginners] another type problem

[Alexey Shmalko]

Try fromMaybe [1]. Examples

Prelude Data.Maybe> fromMaybe [] (Just [1,2,3])
[1,2,3]
Prelude Data.Maybe> fromMaybe [1,2,3] Nothing
[1,2,3]

[1]:
https://hackage.haskell.org/package/base-4.8.0.0/docs/Data-Maybe.html#v:fromMaybe

On Tue, May 12, 2015 at 5:28 PM Roelof Wobben <r.wobben at home.nl> wrote:

>  Oke,
>
> And how do I do this.  Haskell is a difficult one to learn,
>
> Roelof
>
>
>
> Alexey Shmalko schreef op 12-5-2015 om 16:24:
>
> Before cons'ing the result of init', you should check whether it's Just or
> Nothing. What you're doing now is something along the line with 5 : Just 3
> -- this won't typecheck.
>
> On Tue, May 12, 2015 at 5:22 PM Roelof Wobben <r.wobben at home.nl> wrote:
>
>>  Brandon Allbery schreef op 12-5-2015 om 16:16:
>>
>>  On Tue, May 12, 2015 at 10:11 AM, Roelof Wobben <r.wobben at home.nl>
>> 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
>> allbery.b at gmail.com
>> ballbery at sinenomine.net
>> unix, openafs, kerberos, infrastructure, xmonad
>> http://sinenomine.net
>>
>>
>> _______________________________________________
>> Beginners mailing listBeginners at haskell.orghttp://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
>>
>>
>>  What is then the right way to do. I still do not understand what you
>> are trying to make clear to me.
>>
>>
>> Roelof
>>
>>
>>
>>
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