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Today's Topics:
1. Re: tower hanoi problem (Roelof Wobben)
2. Re: tower hanoi problem
(Sumit Sahrawat, Maths & Computing, IIT (BHU))
3. Re: tower hanoi problem (Roelof Wobben)
4. Re: tower hanoi problem (Dudley Brooks)
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Message: 1
Date: Tue, 17 Feb 2015 18:09:38 +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
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Message: 2
Date: Tue, 17 Feb 2015 23:37:50 +0530
From: "Sumit Sahrawat, Maths & Computing, IIT (BHU)"
<[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
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hanoi 1 p1 _ p3 = move 1 disc from p1 to p3
hanoi n p1 p2 p3 = move n discs from p1 to p3 using p2 in between
The definition of the first equation is easy. To complete the second
equation, you need to use hanoi again recursively.
I detailed a way to complete the second equation in my previous mail (which
hopefully didn't spoil it).
Hope this helps.
On 17 February 2015 at 22:39, Roelof Wobben <[email protected]> wrote:
> Stupid error
>
> Then it must be like this :
>
> hanoi n 1 2 3
> | n = 1 -> moves the last disk to the goal peg
> | n > 1 -> moves all the other disk to the spare peg or to the moves
> n -1 to the goal peg
>
>
> Roelof
>
>
> Mike Meyer schreef op 17-2-2015 om 17:57:
>
> On Feb 17, 2015 10:50 AM, "Roelof Wobben" <[email protected]> wrote:
> >
> > N reprent the number of disk
>
> So how does moving 0 disks happen? That is what your first case deals with.
>
> > Roelof
> >
> >
> > Mike Meyer schreef op 17-2-2015 om 17:47:
> >>
> >>
> >> On Feb 17, 2015 10:18 AM, "Roelof Wobben" <[email protected]> wrote:
> >> >
> >> > This part I understand well.
> >> >
> >> > So you could do something like this:
> >> >
> >> > hanoi n 1 2 3
> >> > | n = 0 -> moves the last disk to the goal peg
> >> > | n != 0 -> moves all the other disk to the spare peg or to the
> moves n -1 to the goal peg
> >>
> >> What does n represent here?
> >>
> >>
> >>
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> >
> >
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--
Regards
Sumit Sahrawat
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Message: 3
Date: Tue, 17 Feb 2015 19:43:47 +0100
From: Roelof Wobben <[email protected]>
To: [email protected], The Haskell-Beginners Mailing
List - Discussion of primarily beginner-level topics related to
Haskell <[email protected]>
Subject: Re: [Haskell-beginners] tower hanoi problem
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Message: 4
Date: Tue, 17 Feb 2015 11:42:59 -0800
From: Dudley Brooks <[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]>
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Um ... To the other people giving hints: Don't forget that in the
sequence *of lines in the program* you have to state the base case(s)
*first*, certainly in Haskell, which goes through the lines in order,
until it finds a match.
That's what I meant when I said "first do the base case(s), then the
rest": first *in the program order*, if not necessarily in the
conceptual structure. So for the depth-first binary tree which Joel
Neely pointed out, *first* you must deal with the base case that the
node being looked at is actually a leaf; *only then* can you deal with
the fact that in general the algorithm has the structure <process left
descendants><process this node><process right descendants>.
So if you try <move stack off of bottom><move bottom><place stack on
bottom>, the first part will either enter an endless loop or will
generate an error, because it doesn't have a base case. (No pun on
"base" intended.)
On 2/17/15 4:05 AM, Joel Neely wrote:
> ?Let's tweak your answers? just a bit, calling the three pegs the
> "source", "goal", and "spare" pegs:
>
> On Tue, Feb 17, 2015 at 5:23 AM, Roelof Wobben <[email protected]
> <mailto:[email protected]>> wrote:
>
> - Where do I move the bottom (largest disk) ?
>
> To the last peg, which do not contain any disk then
> ? .
>
>
> From the source peg to the goal peg, which will
> /must
> not contain any disks.?
>
> ?
>
>
> - What must happen before I can move the bottom disk ?
>
> I have to move the disk which above that disk.
>
>
> Move everything else from ____ to ____.?
>
>
> - What must happen after I move the bottom disk ?
>
> All the other disk must be placed above that disk.
>
>
> ? Move everything else from ____ to ____.?
>
> ?So more questions/hints:
>
> 1. How do you fill in the blanks?
> 2. How do you put the three statements in order?
> 3. How many disks does each statement talk about?
>
>
> -jn-
> ?
>
>
>
> --
> Beauty of style and harmony and grace and good rhythm depend on
> simplicity. - Plato
>
>
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