Hi Laurent,
> I am playing around with Problem 35 on Project Euler and just stumbled on
> this:
>
> (de split-number (N)
> (mapcar format (chop (format N))) )
>
> (de all-rotations (N)
> (let SN (split-number N)
> (make
> (for L (range 1 (length SN))
> (link (rot SN))
> (println SN) ) ) ) )
>
> : (all-rotations 123)
> (3 1 2)
> (2 3 1)
> (1 2 3)
> -> ((1 2 3) (1 2 3) (1 2 3))
>
> I can't understand why I do not get the same result as the println.
The problem is that 'rot' is a "destructive" function, i.e. it modifies
its list argument. You could use 'copy' to avoid this.
I would write
(de split-number (N)
(mapcar format (chop N)) )
(de all-rotations (N)
(let SN (split-number N)
(make
(do (length SN)
(link (copy (rot SN)))
(println SN) ) ) ) )
(two minor optimizations: 'chop' can also directly work on a number, and
'L' is not needed in the loop).
Cheers,
- Alex
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