<div dir="ltr">Don't worry. Keep these points in mind and re-read my previous mail.<div><br></div><div>Regarding data vs. type constructors.</div><div><br></div><div>1) Leaf :: MessageTree (Leaf is a MessageTree)</div><div>2) MessageTree is a type constructor (takes types and gives new types)</div><div>3) Node is a data constructor (takes values and gives a new MessageTree)</div><div><br></div><div>Regarding insertion.</div><div><br></div><div>1) The "insert" function takes a message and tree, and returns a tree with that message inserted into it</div><div>2) We absolutely have to provide it a tree</div><div>3) If we insert an invalid message in the tree, it does not get added. Then we get ..... the same tree back.</div><div><br></div><div>If you still cannot see a problem in your code, ask yourself the following:</div><div><br></div>1) What type does the output of insert (MessageTree Leaf) have, and what type should it have<br>2) What happens if we insert an invalid string in a non-empty tree (according to your code)<div><br><div>Don't forget to re-read the previous mail.</div><div>Hope this drives the point home.</div></div></div><div class="gmail_extra"><br><div class="gmail_quote">On 28 February 2015 at 22:59, 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:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
<div>Sorry, <br>
<br>
But I do not understand what you mean. <br>
<br>
What I try to do is this <br>
<br>
If you have a LogMessage which contains " This is not the right
format " then the LogMessage is not inserted in the tree. <br>
Every other message are inserted in the tree.<br>
<br>
So that is why I make a MessageTree with only one Leaf. <br>
<br>
Roelof<br>
<br>
<br>
<br>
Sumit Sahrawat, Maths & Computing, IIT (BHU) schreef op
28-2-2015 om 16:08:<br>
</div><div><div class="h5">
<blockquote type="cite">
<div dir="ltr">You're missing an argument to insert, assuming that
it is indeed there, consider this:
<div><br>
</div>
<div><font face="monospace, monospace"> insert msg tree =
tree'</font></div>
<div><span style="font-family:monospace,monospace"> where
tree' = undefined</span></div>
<div><font face="monospace, monospace"> -- Take a LogMessage
(msg) and a MessageTree (tree)</font></div>
<div><font face="monospace, monospace"> -- and return a new
MessageTree (tree')</font></div>
<div><font face="monospace, monospace"><br>
</font></div>
Therefore, the result of insert in your case, i.e. "MessageTree
Leaf" should be of type MessageTree.<br>
And thus, we get
<div><font face="monospace, monospace"><br>
</font></div>
<div><font face="monospace, monospace"> MessageTree Leaf ::
MessageTree</font></div>
<div><font face="monospace, monospace"> -- Takes a (Leaf ::
LogMessage) and produces a MessageTree</font></div>
<div><font face="monospace, monospace"><br>
</font></div>
which implies,
<div><font face="monospace, monospace"><br>
</font></div>
<div><font face="monospace, monospace"> MessageTree ::
LogMessage -> MessageTree</font></div>
<div><font face="monospace, monospace"> -- A Data constructor</font></div>
<div><font face="monospace, monospace"><br>
</font></div>
Obviously no such data constructor exists. A data constructor of
this type would exist only if you wrote something like:
<div><br>
</div>
<div><font face="monospace, monospace"> data MessageTree =
MessageTree LogMessage</font></div>
<div><span style="font-family:monospace,monospace">
| ...</span></div>
<div><span style="font-family:monospace,monospace"><br>
</span></div>
which would not make sense.</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">On 28 February 2015 at 19:09, 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:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
<div>I tried this : <br>
<span> <br>
insert :: LogMessage -> MessageTree ->
MessageTree<br>
</span> insert s = <br>
case words s of <br>
(_:_: "This is not the right format") ->
MessageTree Leaf <br>
_ ->
MessageTree Node LogMessage Leaf <br>
<br>
<br>
But I see this errormessages which I do not understand :
<br>
<br>
<br>
<div>
<div>src/LogAnalysis.hs@38:49-38:60 </div>
<div><span>Not in scope: data constructor </span>
<div style="font-size:14px"><span>MessageTree</span></div>
</div>
</div>
<div>
<div>src/LogAnalysis.hs@39:49-39:60 </div>
<div><span>Not in scope: data constructor </span>
<div style="font-size:14px"><span>MessageTree<br>
<br>
</span></div>
</div>
</div>
<br>
<br>
Mike Meyer schreef op 28-2-2015 om 12:17:<br>
</div>
<div>
<div>
<blockquote type="cite">
<div dir="ltr">
<div class="gmail_extra">
<div class="gmail_quote">On Sat, Feb 28, 2015 at
5:07 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:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
<div><br>
That part I understand .<br>
<br>
it's more how I do it here :<br>
<br>
Lets say I have this : <br>
<br>
data MessageType = Info<br>
| Warning<br>
| Error Int<br>
deriving (Show, Eq)<br>
<br>
type TimeStamp = Int<br>
<br>
data LogMessage = LogMessage MessageType
TimeStamp String<br>
| Unknown String<br>
deriving (Show, Eq)<br>
<br>
data MessageTree = Leaf<br>
| Node MessageTree
LogMessage MessageTree<br>
deriving (Show, Eq)<br>
<br>
Now I have to put all the LogMessages in
a binary tree.<br>
with this signature : insert ::
LogMessage -> MessageTree ->
MessageTree<br>
<br>
I think I need recursion here but I
still not see how I can make the
clauses. <br>
Normally you can say somethig like this
[] -> 0 or 1 -> but here it
seems to be all seperate logMessages <br>
</div>
</div>
</blockquote>
<div><br>
</div>
<div>Whether you need recursion or not depends
on where you're to insert the message. For
instance, you could turn them into a list
with:</div>
<div><br>
</div>
<div>insert message tree = Node tree message
Leaf</div>
<div><br>
</div>
<div>Try drawing a few pictures of what that
produces, and you'll see why it's probably
not what you want.</div>
<div><br>
</div>
<div>You should be able to tell by looking at
the MessageTree type that you have two
cases: one where you're passed something
matching a Node, and one where you're passed
something that's just a Leaf. The latter
can't be recursive, so it's going to
terminate any recursion. Following the
advice given to you for the Hanoi problem,
try writing it first.</div>
<div><br>
</div>
<div>Then all you have to do is figure out how
to handle the case where you're given a Node
instead of a Leaf. Figuring out where in
the MessageTree you want to insert the
Logmessage will probably be required to do
that.<br>
</div>
</div>
</div>
</div>
</blockquote>
<br>
</div>
</div>
</div>
<br>
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<br>
</blockquote>
</div>
<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>
</div>
</blockquote>
<br>
</div></div></div>
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<br></blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature"><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>
</div>