<div dir="ltr"><div><div><div><div>Why not just?<br><br>==================<br></div>init' [] = Nothing<br></div>init' xs = Just xs<br>==================<br><br></div><div>Meets your type sig and is also has a time complexity of O(1) instead of O(n) which will be the time complexity in the solution involving fromMaybe. Maybe I'm missing something.<br></div><div><br></div>Perhaps it'd help us help you if you'd be a bit more clear on what you want to achieve. </div></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, May 12, 2015 at 9:01 PM, Sumit Sahrawat, Maths & Computing, IIT (BHU) <span dir="ltr"><<a href="mailto:sumit.sahrawat.apm13@iitbhu.ac.in" target="_blank">sumit.sahrawat.apm13@iitbhu.ac.in</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div class="gmail_extra"><div class="gmail_quote"><span class="">On 12 May 2015 at 20:14, Roelof Wobben <span dir="ltr"><<a href="mailto:r.wobben@home.nl" target="_blank">r.wobben@home.nl</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
<div>Thanks, <br>
<br>
The right solution was this : <br>
<br>
init' (x:xs) = Just (x:fromMaybe xs (init' xs))<br>
<br>
if I understand it right x:fromMaybe xs takes care that from xs
the just or Nothing is removed ?<br>
<br></div></div></blockquote><div><br></div></span>Trying it out in ghci,<div><br></div><div>fromMaybe [1,2] Nothing == [1,2]</div><div>fromMaybe [1,2] Just [3] == [3]</div><div><br></div><div>It seems like that should indeed work.</div><div><div class="h5"><div><br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div bgcolor="#FFFFFF" text="#000000"><div>
Roelof<br>
<br>
<br>
<br>
Alexey Shmalko schreef op 12-5-2015 om 16:33:<br>
</div><div><div>
<blockquote type="cite">
<div dir="ltr">Try fromMaybe [1]. Examples<br>
<br>
<div>Prelude Data.Maybe> fromMaybe [] (Just [1,2,3])</div>
<div>[1,2,3]</div>
<div>Prelude Data.Maybe> fromMaybe [1,2,3] Nothing</div>
<div>[1,2,3]</div>
<div><br>
</div>
<div>[1]: <a href="https://hackage.haskell.org/package/base-4.8.0.0/docs/Data-Maybe.html#v:fromMaybe" target="_blank">https://hackage.haskell.org/package/base-4.8.0.0/docs/Data-Maybe.html#v:fromMaybe</a><br>
</div>
</div>
<br>
<div class="gmail_quote">On Tue, May 12, 2015 at 5:28 PM Roelof
Wobben <<a href="mailto:r.wobben@home.nl" target="_blank">r.wobben@home.nl</a>> wrote:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
<div>Oke, <br>
<br>
And how do I do this. Haskell is a difficult one to
learn,<br>
<br>
Roelof<br>
<br>
<br>
<br>
Alexey Shmalko schreef op 12-5-2015 om 16:24:<br>
</div>
</div>
<div bgcolor="#FFFFFF" text="#000000">
<blockquote type="cite">
<div dir="ltr">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.<br>
</div>
<br>
<div class="gmail_quote">On Tue, May 12, 2015 at 5:22 PM
Roelof Wobben <<a href="mailto:r.wobben@home.nl" target="_blank">r.wobben@home.nl</a>>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
<div>Brandon Allbery schreef op 12-5-2015 om 16:16:<br>
</div>
</div>
<div bgcolor="#FFFFFF" text="#000000">
<blockquote type="cite">
<div dir="ltr">
<div class="gmail_extra">
<div class="gmail_quote">On Tue, May 12, 2015
at 10:11 AM, Roelof Wobben <span dir="ltr"><<a href="mailto:r.wobben@home.nl" target="_blank">r.wobben@home.nl</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
<div>I do not understand what you are
saying to me.<br>
<br>
I know that init produces a Maybe [a]
. That is why I did put a Just before
it.<br>
</div>
</div>
</blockquote>
<div><br>
</div>
<div>You are invoking it again though, and
using its result as if it produces [a]
instead of Maybe [a].</div>
</div>
<div><br>
</div>
-- <br>
<div>
<div dir="ltr">
<div>brandon s allbery kf8nh
sine nomine associates</div>
<div><a href="mailto:allbery.b@gmail.com" target="_blank">allbery.b@gmail.com</a>
<a href="mailto:ballbery@sinenomine.net" target="_blank">ballbery@sinenomine.net</a></div>
<div>unix, openafs, kerberos,
infrastructure, xmonad <a href="http://sinenomine.net" target="_blank">http://sinenomine.net</a></div>
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<div bgcolor="#FFFFFF" text="#000000"> What is then
the right way to do. I still do not understand what
you are trying to make clear to me.</div>
<div bgcolor="#FFFFFF" text="#000000"><br>
<br>
Roelof</div>
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<br></blockquote></div></div></div><span class="HOEnZb"><font color="#888888"><br><br clear="all"><div><br></div>-- <br><div><div dir="ltr"><div><div dir="ltr"><div dir="ltr"><div>Regards</div><div dir="ltr"><div><br></div><div>Sumit Sahrawat</div></div></div></div></div></div></div>
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