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 <allbery.b@gmail.com> wrote:
On Tue, May 12, 2015 at 10:11 AM, Roelof Wobben <r.wobben@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@gmail.com                                  ballbery@sinenomine.net
unix, openafs, kerberos, infrastructure, xmonad        http://sinenomine.net

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Regards

Sumit Sahrawat