I have attached the latest and greatest bffind_root to this email.
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From: "Richard Hennessy" <rich.hennessy at verizon.net>
Sent: Saturday, May 29, 2010 7:38 PM
To: "Barton Willis" <willisb at unk.edu>; "Maxima List" <maxima at math.utexas.edu>
Subject: Re: [Maxima] How to pass a power series to find_root
> Okay I think I understand that nfloat() isn't helping but what about how to prevent evaluation of a function passed as
> a parameter to another function. makelist(f(5.9b-9, e), e, 1, 100) does not take a long time. In fact it is pretty
> fast. Something is different about makelist(). I think I remember reading that makelist was "designed for functions"
> in some of the documents on the Wiki.
>
> I have a bffind_root() function that I wrote and when I call it it takes so long that I have yet to see it complete.
> bffind_root() is defined in pw.mac. It is just a simple binary search. I have tried all kind of quoting of the f()
> like '(f(5.9,e)) but it does not work. Typing in f(5.9b-9,e) also never completes which makes sense.
>
> I have changed bffind_root() to take the function name as an extra parameter and that works but I would prefer a
> better way.
>
> This is my power series.
>
> f(x,e):=sum(
> block([hbar : bfloat(6.6260693b-34/(2*%pi)), mu : 1b15, m : 9.109389754b-31],
> if equal(_i ,0) then
> (
> a : 1,
> acc : 1,
> am2 : 0,
> am4 : 0,
> am6 : 0
> )
> elseif mod( _i , 2)=0 then
> (
> a : 2 * m / hbar^2 * (mu * am6 - am2 * e)/(_i * (_i - 1))
> ),
> if mod(_i , 2)=1 then
> (
> _num : 0
> )
> else
> (
> am6 : am4,
> am4 : am2,
> am2 : a,
> tmp : a*acc,
> acc : acc * x^2,
> _num : tmp
> ),
> _num
> ), _i, 0, 300)$
>
> bffind_root('f(5.9b-9, e), f, e, 4.047b-19,4.4947335b-19,30); this works fine because I modified bffind_root() to
> pass the function name as the second parameter.
>
> bffind_root('f(5.9b-9, e), e, 4.047b-19,4.4947335b-19,30); this takes forever.
>
> find_root('f(5.9e-9, e), e, 4.047e-19,4.4947335e-19); this takes forever.
>
> Thanks for advance for any help.
>
> Rich
>
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