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Today's Topics:
1. Re: trees on Haskell : Do I understand it right ? (Joel Neely)
2. Re: trying to install libraries for Haskell School of
Expression (emacstheviking)
3. Re: trees on Haskell : Do I understand it right ? (Roelof Wobben)
----------------------------------------------------------------------
Message: 1
Date: Sun, 1 Mar 2015 07:45:24 -0600
From: Joel Neely <[email protected]>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <[email protected]>
Subject: Re: [Haskell-beginners] trees on Haskell : Do I understand it
right ?
Message-ID:
<CAEEzXAi=tn_+wmyqfqhn7pujvv0gc-nxt3g3kcu6ogw_fqt...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
Roelof,
Perhaps it would help for you to draw diagrams for the cases you're working.
If a leaf has nothing below it, and a node always has exactly three things
below it (the left child, the message, and the right child),
what would your picture look like for 1, 2, and 3 nodes?
And how would you write out constructor expressions that match those shapes?
Hope that helps,
-jn-
On Thu, Feb 26, 2015 at 12:32 PM, Roelof Wobben <[email protected]> wrote:
> Oke,
>
> I send it a second time but now in plain text.
>
> So for 3 it will be like this :
>
> Node = Node (Node Leaf "msg1" Leaf) (Node Leaf "msg2") (Node "msg3"
> Leaf) ???
>
>
> Roelof
>
>
>
>
>
> Konstantine Rybnikov schreef op 26-2-2015 om 15:08:
>
> In my second example you can see a minimal node with a message:
>
> node = Node Leaf "msg" Leaf
>
> Instead of either left or right Leaf you can put another value of type
> MessageTree, for example:
>
> node = Node Leaf "msg1" (Node Leaf "msg2" Leaf)
>
> On Thu, Feb 26, 2015 at 4:01 PM, Roelof Wobben <[email protected]> wrote:
>
>> Oke,
>>
>> So a leaf is a node which has no "branch"
>>
>> I have made a exercise where I have to made the logMessages.
>> Now I have to turn them into a tree
>>
>> Where does the second entry goes then ?
>>
>> Roelof
>>
>>
>> Konstantine Rybnikov schreef op 26-2-2015 om 14:56:
>>
>> Hi Roelof,
>>
>> I think you misunderstood it.
>>
>> There are two things here: types and values (value-constructors). They
>> exist in different world, not touching each other.
>>
>> In Haskell, you define a type as:
>>
>> data <Type_Name> = <ValueConstructor_Name> <Type_Name> <Type_Name>
>> <Type_Name>
>>
>> You can create values as:
>>
>> let varName = <ValueConstructor_Name> <Value> <Value> <Value>
>>
>> You need to put <Value> of some type, not type name itself in place of
>> those <Value>s.
>>
>> So, with datatype you provided, you have two data-constructors:
>>
>> Leaf
>>
>> and
>>
>> Node <val> <val> <val>
>>
>> You can create a leaf:
>>
>> let leaf = Leav
>>
>> or a node:
>>
>> let node = Node Leaf "msg" Leaf
>>
>> You can see that Node is a data-constructor that takes 3 values, not
>> type-names as it's parameters.
>>
>> Hope this helps.
>>
>> On Thu, Feb 26, 2015 at 3:21 PM, Roelof Wobben <[email protected]> wrote:
>>
>>> Hello,
>>>
>>> Suppose we have this definition of a tree :
>>>
>>> data MessageTree = Leaf
>>> | Node MessageTree LogMessage MessageTree
>>> deriving (Show, Eq)
>>>
>>> let Message = LogMessage "E 1 this is a test error"
>>> let Message = LogMessage "e 2 this is the second test error "
>>>
>>> As I understand it right I can make the first entry like this :
>>> first_entry = Node Messagetree Message Messagetree
>>>
>>> And the second one like this second_entry = Node Message Messagetree
>>> Message2 Messagetree ??
>>>
>>> Roelof
>>>
>>> _______________________________________________
>>> Beginners mailing list
>>> [email protected]
>>> http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
>>>
>>
>>
>>
>> _______________________________________________
>> Beginners mailing
>> [email protected]http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
>>
>>
>>
>> _______________________________________________
>> Beginners mailing list
>> [email protected]
>> http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
>>
>>
>
>
> _______________________________________________
> Beginners mailing
> [email protected]http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
>
>
>
>
> _______________________________________________
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>
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--
Beauty of style and harmony and grace and good rhythm depend on simplicity.
- Plato
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Message: 2
Date: Sun, 1 Mar 2015 14:56:44 +0000
From: emacstheviking <[email protected]>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <[email protected]>
Subject: Re: [Haskell-beginners] trying to install libraries for
Haskell School of Expression
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<CAEiEuUJim7h=vyr0hnwolvb_tegyamikrz9uwsjbsgam9b+...@mail.gmail.com>
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I feel your pain...
> Confession: I abandoned Haskell two years ago because of frustration with
> cabal and hackage. I decided to get back to the language today, and to
> start with Haskell School of Expression. I immediately run into the problem
> that the first thing I try to install with cabal does not work.
>
> It is the same reason I have stopped using it. It's a real shame. Those
with better education and understanding than mine should be concerned that
the uptake of the language is stunted by its package manager.
I love Haskell. I have taught myself (the beginnings at least) of group
theory just to better comprehend the mindset of monads. For that alone I am
glad I learned Haskell as it has rekindled my interest in maths!
> Thanks for any help. Please tell me things are not just as bad now as they
> were when I left ;-)
>
> This mail seems to indicate to me that "cabal hell" is here for some time
to come...
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------------------------------
Message: 3
Date: Sun, 01 Mar 2015 19:08:22 +0100
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] trees on Haskell : Do I understand it
right ?
Message-ID: <[email protected]>
Content-Type: text/plain; charset=windows-1252; format=flowed
Hello,
Im looking for goofd online software to make the diagrams.
As soon as I find it . I will publish them on the ML.
Roelof
Joel Neely schreef op 1-3-2015 om 14:45:
> Roelof,
>
> Perhaps it would help for you to draw diagrams for the cases you're
> working.
> If a leaf has nothing below it, and a node always has exactly three
> things below it (the left child, the message, and the right child),
> what would your picture look like for 1, 2, and 3 nodes?
> And how would you write out constructor expressions that match those
> shapes?
>
> Hope that helps,
> -jn-
>
>
> On Thu, Feb 26, 2015 at 12:32 PM, Roelof Wobben <[email protected]
> <mailto:[email protected]>> wrote:
>
> Oke,
>
> I send it a second time but now in plain text.
>
> So for 3 it will be like this :
>
> Node = Node (Node Leaf "msg1" Leaf) (Node Leaf "msg2") (Node
> "msg3" Leaf) ???
>
>
> Roelof
>
>
>
>>
>>
>> Konstantine Rybnikov schreef op 26-2-2015 om 15:08:
>>> In my second example you can see a minimal node with a message:
>>>
>>> node = Node Leaf "msg" Leaf
>>>
>>> Instead of either left or right Leaf you can put another value
>>> of type MessageTree, for example:
>>>
>>> node = Node Leaf "msg1" (Node Leaf "msg2" Leaf)
>>>
>>> On Thu, Feb 26, 2015 at 4:01 PM, Roelof Wobben <[email protected]
>>> <mailto:[email protected]>> wrote:
>>>
>>> Oke,
>>>
>>> So a leaf is a node which has no "branch"
>>>
>>> I have made a exercise where I have to made the logMessages.
>>> Now I have to turn them into a tree
>>>
>>> Where does the second entry goes then ?
>>>
>>> Roelof
>>>
>>>
>>> Konstantine Rybnikov schreef op 26-2-2015 om 14:56:
>>>> Hi Roelof,
>>>>
>>>> I think you misunderstood it.
>>>>
>>>> There are two things here: types and values
>>>> (value-constructors). They exist in different world, not
>>>> touching each other.
>>>>
>>>> In Haskell, you define a type as:
>>>>
>>>> data <Type_Name> = <ValueConstructor_Name> <Type_Name>
>>>> <Type_Name> <Type_Name>
>>>>
>>>> You can create values as:
>>>>
>>>> let varName = <ValueConstructor_Name> <Value> <Value> <Value>
>>>>
>>>> You need to put <Value> of some type, not type name itself
>>>> in place of those <Value>s.
>>>>
>>>> So, with datatype you provided, you have two data-constructors:
>>>>
>>>> Leaf
>>>>
>>>> and
>>>>
>>>> Node <val> <val> <val>
>>>>
>>>> You can create a leaf:
>>>>
>>>> let leaf = Leav
>>>>
>>>> or a node:
>>>>
>>>> let node = Node Leaf "msg" Leaf
>>>>
>>>> You can see that Node is a data-constructor that takes 3
>>>> values, not type-names as it's parameters.
>>>>
>>>> Hope this helps.
>>>>
>>>> On Thu, Feb 26, 2015 at 3:21 PM, Roelof Wobben
>>>> <[email protected] <mailto:[email protected]>> wrote:
>>>>
>>>> Hello,
>>>>
>>>> Suppose we have this definition of a tree :
>>>>
>>>> data MessageTree = Leaf
>>>> | Node MessageTree LogMessage MessageTree
>>>> deriving (Show, Eq)
>>>>
>>>> let Message = LogMessage "E 1 this is a test error"
>>>> let Message = LogMessage "e 2 this is the second test
>>>> error "
>>>>
>>>> As I understand it right I can make the first entry
>>>> like this : first_entry = Node Messagetree Message
>>>> Messagetree
>>>>
>>>> And the second one like this second_entry = Node
>>>> Message Messagetree Message2 Messagetree ??
>>>>
>>>> Roelof
>>>>
>>>> _______________________________________________
>>>> Beginners mailing list
>>>> [email protected] <mailto:[email protected]>
>>>> http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
>>>>
>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> Beginners mailing list
>>>> [email protected] <mailto:[email protected]>
>>>> http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
>>>
>>>
>>> _______________________________________________
>>> Beginners mailing list
>>> [email protected] <mailto:[email protected]>
>>> http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> Beginners mailing list
>>> [email protected] <mailto:[email protected]>
>>> http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
>>
>
>
> _______________________________________________
> Beginners mailing list
> [email protected] <mailto:[email protected]>
> http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
>
>
>
>
> --
> Beauty of style and harmony and grace and good rhythm depend on
> simplicity. - Plato
>
>
> _______________________________________________
> Beginners mailing list
> [email protected]
> http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
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