Guile code for L-system

Guile code for L-system

[Giancarlo Bassi]

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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Re: Guile code for L-system

[Dave Griffiths]

> 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.

I don't know if you are asking, but I have some code to do this (with
strings rather than lists though) here:
http://cvs.savannah.gnu.org/viewcvs/livenoisetools/livenoisetools/pattern-cascade/lsys.scm?view=markup

I've been using it to generate music for live performaces. FWIW I've
written this code in C++, python and now scheme, which has turned out to
be a lot more elegant, as usual :)

cheers,

dave




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Re: Guile code for L-system

[Neil Jerram]

Giancarlo Bassi <g.bassi@iperbole.bologna.it> writes:

> 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)

(define (iterate l)
  (apply append
         (map (lambda (x)
                (case x
                  ((a) '(b))
                  ((b) '(a b))))
              l)))
>
> 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.

I'm afraid you've lost me here.

    Neil 



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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
>
>
>
>
> _______________________________________________
> Guile-user mailing list
> Guile-user@gnu.org
> http://lists.gnu.org/mailman/listinfo/guile-user



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