Re: Guile code for L-system

[Scott W. Dunlop]

The most succinct expansion implementation I could think of, in pure  
Scheme:

(define (expand-l-term term axioms)
  (let ((axiom (assq term axioms)))
    (if axiom
      (cdr axiom)
      (list term))))

(define (expand-l-expr expr axioms)
  (apply append (map (lambda (term)
                       (expand-l-term term axioms))
                     expr)))

>> (expand-l-expr '(b a b) '((a b) (b a b)))
:: (a b b a b)

--Scott.

On May 24, 2006, at 9:02 AM, Giancarlo Bassi wrote:

> I want to write in Guile the code implementing these following  
> rewriting rules, which are taken from L-system rewriting (from  
> Lindenmayer's
> "Algorithmic beauty of plants")
>
> Axiom a
> a -> b
> b -> ab
>
> So, it should be create these lists
>
> `(a) `(b) `(a b) `(b a b) `(a b b a b)  `(b a b a b b a b)
>
> You may notice that the lists' length are Fibonacci's number.
>
> This drill should introduce my final purpose to write the
> Guile code for the Hilbert-Peano's curve, which in L-system
> looks as:
>
> Axiom x
> x -> - f y + x f x + f y -
> y -> + x f - y f y - f x +
>
> where f means a translation and + - are rotations.
>
>
> Then I'll be able to write the drgeo script for actually drawing that
> curve, which looks as limit for the number of iterations to infinity.
>
> Thanks a lot.
>                 GB
>
> ---
> "I'm no Pawn, I'm Donald Duck ! "
>        -- Donald in MathMagic Land
>
>
>
>
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