[Haskell-beginners] Difficulty understanding the Towers of Hanoi exercise from CIS194

[Petr Vápenka]

The tower of hanoi function you are writing is doing the "move n discs from
peg A to peg C using peg B" stuff.

1. moving n-1 discs doesn't mean moving them in one step, but rather using
the proper sequence of moves that results in (n-1) discs to be moved
2. after you've moved n-1 discs, only one disc is left on the peg and it is
the largest disc from the set of n discs
3. do the same as in point 1

Try to translate the steps literally to code, it will work and
understanding will come after that :)

Best, PV

On Sun, Aug 30, 2015 at 8:27 AM, John Del Rosario <john2x at gmail.com> wrote:

> I've just completed the first exercise (Credit Card Number Validation)
> and was quite happy with myself.
>
> But moving on to the next exercise I found myself having trouble trying
> to understand some parts of the question.
>
> I've solved Towers of Hanoi before with an imperative language,
> but I'm having trouble visualising the steps described in this paragraph:
>
> To move n discs (stacked in increasing size) from peg a to peg b using peg
> c
> as temporary storage,
> 1. move n-1 discs from a to c using b as temporary storage
> 2. move the top disc from a to b
> 3. move n-1 discs from c to b using a as temporary storage.
>
> I've never seen the solution described this way before.
> So if I start with 5 discs, then for the first step I'll be moving 4 (n-1)
> discs? But
> can't I only move 1 disc at a time?
>
> And step 2 says to move the top disc from a to b. Which disc is the top
> disc at this point?
>
> I'm still in a very imperative mindset (and having no formal training
> doesn't help),
> but I'm hoping that will improve as I go through this course!
>
>
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