Hello Robert,
there is a further report concerning the erf function on the Sage website.
Because we have extended the erf function to calculate results for complex
values we now get:
(%i14) build_info();
Maxima version: 5.16.0cvs
Maxima build date: 0:34 12/23/2008
host type: @host@
lisp-implementation-type: GNU Common Lisp (GCL)
lisp-implementation-version: GCL 2.6.8
(%i15) erf(%i);
(%o15) erf(%i)
(%i16) erf(%i),numer;
(%o16) 1.650425758797543 %i + 2.1207839599929513E-16
That is the report from the Sage project:
Expected:
-.8862269254527579*%i*erf(%i)
Got:
-.8862269254527579*%i*(1.650425758797543*%i+1.110223024625156E-16)
erf(%i) is now evaluated and the result for the above expression is
approximately real.
(%i17) erf(3*%i);
(%o17) erf(3 %i)
(%i18) erf(3*%i),numer;
(%o18) 1629.99462260308 %i + 1.7793504802297391E-12
That is the report from the Sage project
Expected:
Traceback (most recent call last):
...
TypeError: unable to simplify to complex approximation
Got:
(1.110223024625156e-16+1629.9946226005709j)
Thus, Sage now detect an unexpected complex result.
Thus, I do not think that we have errors in Maxima, but Sage get unexpected
results for the erf function with complex arguments.
Remark: We have small realparts in the results. This is due to the limited
numerical accuracy of the routine.
Dieter Kaiser
-----Urspr?ngliche Nachricht-----
Von: maxima-bounces at math.utexas.edu [mailto:maxima-bounces at math.utexas.edu] Im
Auftrag von Robert Dodier
Gesendet: Montag, 22. Dezember 2008 17:20
An: Michael Abshoff; Maxima List
Cc: William Stein
Betreff: Re: [Maxima] Maxima 5.17.1 regressions for Sage
About a problem reported at: http://trac.sagemath.org/sage_trac/ticket/4841
"Bad argument to `genfact'"
What are the arguments to genfact here?
Inspecting the Maxima code, I see the following restriction:
(cond ((and (fixnump a)
(fixnump b)
(fixnump c))
(if (and (> a -1)
(> b -1)
(or (<= c a) (= b 0))
(<= b (/ a c)))
(gfact a b c)
(merror "Bad argument to `genfact'")))
(I.e. when a, b, and c are machine integers)
best
Robert Dodier
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