[Haskell-beginners] tower hanoi problem

[Dudley Brooks]

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 <r.wobben at home.nl 
> <mailto: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 ____ 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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