Karim BELABAS on Mon, 12 May 2003 15:08:51 +0200 (MEST) |
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Re: CVS: seriesprecision too large |
On Sun, 11 May 2003, Ilya Zakharevich wrote: > On Sun, May 11, 2003 at 07:24:42PM +0200, Bill Allombert wrote: > > I think it is 2.2.5 F22: > > 22- for transcendental function f and polynomial p, f(p) only gave > > seriesprecision significant terms when val(p) = 0 > > It is not clear why good behaviour w.r.t. multiplication is prefered > to good behaviour w.r.t. addition. Of course, one needs to make a > choice, but *why* this one? I tried to make it consistent with the handling of t_REALs: '[series | real]precision' is the number of significant [terms | digits] one computes when converting an exact quantity [polynomial | rational number] before an inexact computation. > Did not you notice > > / 1 2 1 4 1 6 1 8 1 10 11 \ > | 1 - -y + --y - ---y + -----y - -------y + O(y ) | x + > \ 2 24 720 40320 3628800 / > > with seriesprecision==9? After the above conversions, computations with inexact terms yield exactly as many terms as can be obtained from these initial (converted) objects. We miss something analogous to 'format' to truncate series to a given number of significant terms on output. It's trivial to implement [ 'seriesformat' ? setting it by default to 'seriesprecision' terms ? ]. I'm not sure how useful it would be. Karim. -- Karim Belabas Tel: (+33) (0)1 69 15 57 48 Dép. de Mathématiques, Bât. 425 Fax: (+33) (0)1 69 15 60 19 Université Paris-Sud http://www.math.u-psud.fr/~belabas/ F-91405 Orsay (France) http://www.parigp-home.de/ [PARI/GP]