Re: cl_N log(const cl_N& a, const cl_N& b) returns zero when an exact negative integer is expected

18 Jun 2004

Hi Niklas!

On Fri, 18 Jun 2004, Niklas Knutsson wrote:
...
the following bug required a workaround when writing source code for
Qalculate!:
cl_N log(const cl_N& a, const cl_N& b) returns zero when an exact
negative integer is expected.
example:
log(recip(cl_RA(1000)), cl_N(10)); returns 0
log(cl_N(0.001), cl_N(10)); returns -3
using
cln-1.1.6
gmp-4.1.2
gcc-3.3.3
glibc-2.3.3_pre20040207
linux-2.6.5-mm1
//niklas k.
Thank you very much for your bugreport.

I have fixed it in CVS.  It turns out to be a one-character fix:

Index: src/rational/transcendental/cl_RA_logp.cc
===================================================================
RCS file: /home/cvs/cln/src/rational/transcendental/cl_RA_logp.cc,v
retrieving revision 1.2
diff -a -u -r1.2 cl_RA_logp.cc

--- src/rational/transcendental/cl_RA_logp.cc   28 Aug 2000 22:08:23 -0000      1.2
+++ src/rational/transcendental/cl_RA_logp.cc   18 Jun 2004 21:33:23 -0000
@@ -50,7 +50,7 @@
                                return cl_false;
                        // a1=1
                        var cl_RA l;
-                       if (logp(a2,b,pl)) {
+                       if (logp(a2,b,&l)) {
                                *pl = -l; return cl_true;
                        } else
                                return cl_false;

Regards
    -richy.
-- 
Richard B. Kreckel
<http://www.ginac.de/~kreckel/>

    