Forgot to reply to the whole list; here is my answer.
> On Wed, May 13, 2009 at 02:00:30PM -0500, Barton Willis wrote:
> (1) If there is a global hashed array L defined, L[i] extracts the value of
> the
> global hashed array, not the member of local list variable L. The fix is to
> replace L[i] with inpart(L,i).
>
I'll keep that in mind.
> (2) Your code is inefficient, I think. Try rewriting rcs as loop:
>
> (%i16) bob(l) := block([s : 0, k : 1],
> for lk in l do (
> s : s + binomial(lk-1,k),
> k : k + 1),
> s + 1)$
>
> (%i28) bob([a,b]);
> (%o28) ((b-2)*(b-1))/2+a
It's really the opposite: Loops are *much* slower!
(%i13) block([s:0], for i from 1 thru 1000000 do s : s + i, s);
Evaluation took 21.9220 seconds (42.0870 elapsed)
(%o13) 500000500000
(%i14) apply("+",create_list(i,i,1,1000000));
Evaluation took 1.4680 seconds (1.4670 elapsed)
(%o14) 500000500000
(And this becomes worse for longer loops; of course, at some
point memory doesn't follow ;-()
> (3) The usage of a Maxima set as an input to rcs seems spurious.
>
sure --- this comes from the context where this is all used.
> (4) As for the calls to ev in your code, I don't want to think about it.
> Ev makes my head hurt.
>
But it seems to be the only possibility in this application?
thanks!
Oliver
> > Barton
> >
> > -----maxima-bounces at math.utexas.edu wrote: -----
> >
> >
> > >Maxima?5.18.1?http://maxima.sourceforge.net
> > >Using?Lisp?ECL?9.4.1
> > >declare(rv,noun)$
> > >rcs(S)?:=?block([L?:?listify(S)],
> > >??apply("+",create_list(binomial(L[i]-1,i),?i,1,length(L)))?+?1)$
> > >(%i4)?ev(rv(1,4),rv([L]):=rcs(setify(L)),nouns);
> > >(%o4)?4
> > >(%i5)?ev(rv(1,5),rv([L]):=rcs(setify(L)),nouns);
> > >(%o5)?7.0
> > >(%i6)?rcs({1,5});
> > >(%o6)?7
> > >
> > >I?hope?you?see?the?disaster:?o6?is?correct,?and?should?be?the?same
> > >as?o5,?but?somehow?suddenly?the?result?is?turned?into?a?floating-point
> > >number?(which?depends?on?the?values?---?doesn't?happen?with?o4).
> > >
> > >I?guess?I?should?submit?this?as?a?bug,?but?wanted?to?hear?some?comments
> > >first.
> > >
> > >(Workarounds??Currently?the?above?behaviour?blocks?a?whole?development;
> > >but
> > >using?floor?doesn't?seem?safe?...)
> > >
> > >Oliver
> > >
> > >_______________________________________________
> > >Maxima?mailing?list
> > >Maxima at math.utexas.edu
> > >http://www.math.utexas.edu/mailman/listinfo/maxima
>
> --
> Dr. Oliver Kullmann
> Computer Science Department
> Swansea University
> Faraday Building, Singleton Park
> Swansea SA2 8PP, UK
> http://cs.swan.ac.uk/~csoliver/
--
Dr. Oliver Kullmann
Computer Science Department
Swansea University
Faraday Building, Singleton Park
Swansea SA2 8PP, UK
http://cs.swan.ac.uk/~csoliver/