[Haskell-beginners] tower hanoi problem

[Sumit Sahrawat, Maths & Computing, IIT (BHU)]

Think of the function,
    hanoi :: Integer -> Peg -> Peg -> Peg -> [Move]

As printing the following moves:

   1. Move (n - 1) discs from peg1 to peg2 using peg3
   2. Move 1 disc from peg1 to peg3 using peg2
   3. Move (n - 1) discs from peg2 to peg3 using peg1

The main idea behind towers of hanoi is that you are constrained, and
cannot move many discs at once. But using an *intermediate peg*, you can
eventually move all discs to the target peg.

On 17 February 2015 at 17:53, Roelof Wobben <r.wobben at home.nl> wrote:

>  Joel Neely schreef op 17-2-2015 om 13:05:
>
>  ​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 <r.wobben at home.nl> 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 source to sparel peg.​
>
>
>>
>> - What must happen after I move the bottom disk ?
>>
>> All the other disk must be placed above that disk.
>>
>
>  ​ Move everything else from spare  to goal.​
>
>
> ​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-
> ​
>
>
> 1. I did already.
> 2.     First move everything except the bottom one to the spare peg.
>         Move the bottom one to the goal peg.
>         Move everything else from the spare peg to the goal peg.
>
> 3. Only 2
>
> Roelof
>
>
>
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-- 
Regards

Sumit Sahrawat
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