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Today's Topics:
1. tower of hanoi problem (Roelof Wobben)
2. tower hanoi problem (Roelof Wobben)
3. Re: tower hanoi problem (Steven Williams)
4. Re: tower hanoi problem (Roelof Wobben)
5. Re: tower of hanoi problem (Mike Meyer)
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Message: 1
Date: Fri, 13 Feb 2015 20:39:29 +0100
From: Roelof Wobben <[email protected]>
To: [email protected]
Subject: [Haskell-beginners] tower of hanoi problem
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Message: 2
Date: Fri, 13 Feb 2015 22:09:19 +0100
From: Roelof Wobben <[email protected]>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <[email protected]>
Subject: [Haskell-beginners] tower hanoi problem
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Message: 3
Date: Fri, 13 Feb 2015 15:16:24 -0600
From: Steven Williams <[email protected]>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <[email protected]>
Subject: Re: [Haskell-beginners] tower hanoi problem
Message-ID: <[email protected]>
Content-Type: text/plain; charset=windows-1252
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Hash: SHA1
I am really horrible at helping people which is why I delayed replying
to this. Your email got through to the list twice, you don't need to
send it again.
The steps you need to take are in the homework assignment. The items
1-3 are literally the algorithm you need to use. Something to keep in
mind is that the pegs can change per function call. For example
initially you call it with "hanoi 2 a b c", then hanoi calls itself
again with "hanoi 1 a c b" to achieve one of the steps that you need
to take.
Steven Williams
My PGP Key: http://pgp.mit.edu/pks/lookup?op=get&search=0xCACA6C74669A54FA
On 02/13/2015 03:09 PM, Roelof Wobben wrote:
> Hello,
>
> After a short break I try to make the next assignment of the CIS
> 194 course. I do self-study.
>
> Lets say we have 1 disk with 2 pegs then we have this :
>
>
> type Peg = String. type Move = (Peg, Peg) Hanoi :: Integer -> Peg
> -> Peg -> [Move]
>
> So I can do this Hanoi 2 a b
>
> How can I proceed further.
>
> I do not see how I can tell that the disk can move from a to b And
> I do not see what the base case will be . I think when a is empty
> and b has a value.
>
> Can anyone shine a light on this matter without telling me the
> answer ?
>
> Roelof
>
> typ
>
>
>
> _______________________________________________ Beginners mailing
> list [email protected]
> http://www.haskell.org/mailman/listinfo/beginners
>
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------------------------------
Message: 4
Date: Fri, 13 Feb 2015 22:25:55 +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] tower hanoi problem
Message-ID: <[email protected]>
Content-Type: text/plain; charset=windows-1252; format=flowed
Thanks,
Is it the second time a c b because the next step will be a disk from
the a to the c disk ?
Roelof
Steven Williams schreef op 13-2-2015 om 22:16:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> I am really horrible at helping people which is why I delayed replying
> to this. Your email got through to the list twice, you don't need to
> send it again.
>
> The steps you need to take are in the homework assignment. The items
> 1-3 are literally the algorithm you need to use. Something to keep in
> mind is that the pegs can change per function call. For example
> initially you call it with "hanoi 2 a b c", then hanoi calls itself
> again with "hanoi 1 a c b" to achieve one of the steps that you need
> to take.
>
> Steven Williams
> My PGP Key: http://pgp.mit.edu/pks/lookup?op=get&search=0xCACA6C74669A54FA
>
> On 02/13/2015 03:09 PM, Roelof Wobben wrote:
>> Hello,
>>
>> After a short break I try to make the next assignment of the CIS
>> 194 course. I do self-study.
>>
>> Lets say we have 1 disk with 2 pegs then we have this :
>>
>>
>> type Peg = String. type Move = (Peg, Peg) Hanoi :: Integer -> Peg
>> -> Peg -> [Move]
>>
>> So I can do this Hanoi 2 a b
>>
>> How can I proceed further.
>>
>> I do not see how I can tell that the disk can move from a to b And
>> I do not see what the base case will be . I think when a is empty
>> and b has a value.
>>
>> Can anyone shine a light on this matter without telling me the
>> answer ?
>>
>> Roelof
>>
>> typ
>>
>>
>>
>> _______________________________________________ Beginners mailing
>> list [email protected]
>> http://www.haskell.org/mailman/listinfo/beginners
>>
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> _______________________________________________
> Beginners mailing list
> [email protected]
> http://www.haskell.org/mailman/listinfo/beginners
>
------------------------------
Message: 5
Date: Fri, 13 Feb 2015 15:54:07 -0600
From: Mike Meyer <[email protected]>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <[email protected]>
Subject: Re: [Haskell-beginners] tower of hanoi problem
Message-ID:
<CAD=7u2ddtsh5_yovjpyyyfyzwdnyfrc_kjawh5_gyr0kmdo...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
On Fri, Feb 13, 2015 at 1:39 PM, Roelof Wobben <[email protected]> wrote:
> Hello,
>
> After a short break I try to make the next assignment of the CIS 194
> course.
> I do self-study.
>
> Lets say we have 1 disk with 2 pegs then we have this :
>
>
> type Peg = String.
> type Move = (Peg, Peg)
> Hanoi :: Integer -> Peg -> Peg -> [Move]
>
> So I can do this Hanoi 2 a b
>
> How can I proceed further.
>
> I do not see how I can tell that the disk can move from a to b
> And I do not see what the base case will be . I think when a is empty and
> b has a value.
>
It's a recursion problem. So you tackle it like any other recursion problem:
? Divide your input into two cases: the terminal one that ends the
recursion and the one you recurse on.
? Decide how to handle the terminal case. In this case, you'll return a
list consisting of one move.
? Decide how to divide the non-terminal case into at least two sub-problems
that are all closer to the terminal case by some measurement.
? Write the code that makes the non-terminal calls and combines their
values to create your return value.
In cases where your function returns a list, the combination is almost
always appending one case to the other.
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