[REBOL] Re: "Towers of Hanoi" : Comments please
From: dockimbel:free at: 19-Feb-2001 19:49
Hi Renaud,
Don't know if i have the "rebol coding spirit" :) but this is how i would write
some parts of your script :
> init: func [
> "Initialisation of the hanoi block"
> n [integer!] "Number of disc to use"
> /local tmp
> ][
> count: make integer! 0;
> tmp: make block! []
> hanoi: make block! []
> for i 1 n 1 [tmp: append tmp i]
> hanoi: reduce [tmp make block! 0 make block! 0]
> ]
; /local tmp i
[
i: count: 0 ; "make integer!" is not necessary.
tmp: make block! n ; pre-allocate n item for the new block.
loop n [ ; 'loop is easier to read and much faster.
append tmp i ; tmp will be modify, no need to re-assign.
i: i + 1
]
hanoi: reduce [tmp copy [] copy []]
]
> first2: func [
> "Return first item, otherwise 99999"
> blk [block!]
> ][
> if (length? blk) = 0 [return 99999]
> return first blk
> ]
[
either empty? blk [99999][first blk]
; you can see 'empty? as a shortcut to 'zero? 'length?
]
> move: func [
> "Move one disc from one stick to another - does not care of game's rules"
> from [integer!]
> to [integer!]
> /local temp tmp
> ][
> temp: make block! [[][][]]
you could also use : array/initial [3 1] []
> tmp: first pick hanoi from
> for i 1 3 1 [
> poke temp i head either i = from [remove hanoi/:i] [either i = to [insert
> head hanoi/:i tmp][hanoi/:i]]
> ]
> count: count + 1
> hanoi: copy temp
> print [count ": move from" from "to" to " : " mold hanoi]
> ]
Your code is a little hard to read here. You should indent it after reading
the "Style Guide" part of the Rebol manual.
(also, not sure that 'head is needed here.)
> play: func [
> "Play nb disc from one place to an other"
> from [integer!] "Place to start from"
> to [integer!] "Place to go to"
> nb [integer!] "How many disc to move"
> /local from_state to_state tmp n
> ][
> tmp: pick [0 0 3 2 1] (from + to)
> either ((length? pick hanoi from) > 0) [
either not empty? pick hanoi from [
> either nb = 1 [
> from_state: pick hanoi from
> to_state: pick hanoi to
> either (first2 from_state) < (first2 to_state)
>
> move from to
> ][
> move to from
> play from to 2
> ]
>
> play from tmp (nb - 1)
> play from to 1
> play tmp to (nb - 1)
> ]
> ][
> print "Can't do that: nothing to move"
> ]
> ]
>
> ; init a game with 4 discs
> init 4
>
> ;play the game
> play 1 3 4
>
Pretty good script for learning Rebol. (A quand une version /View ? ;) )
HTH,
DocKimbel.
