BUG in realrad.lib

[gorzel]

1.) In 2008, a bug was found in realrad.lib

See: Real solutions

​http://www.singular.uni-kl.de/forum/viewtopic.php?f=10&t=1678

Some month ago, I described the problem and how to solve it, put it has not be fixed yet.

Furthermore:

2.) the static proc exp is buggy

proc exp(int a, int b)     // <-- a should be bigint
{
   number res = 1;            // <--this should be bigint
   while (b > 0) {
   if (b mod 2 == 1) {
       res = res * a;
       b = b-1;
   }
   a = a * a;
   b = b div 2;
   }
   return(res);
}

is buggy

> exp(2,34);
// ** int overflow(*), result may be wrong
0

but obsolete.

It is only used in the static proc subsets to compute 2^n,

int grenze=int(exp(2,n))-1;

However this can be done just by

 int grenze = int(bigint(2)^n-1);

Though, a list with MAXINT =2^{31-1 entries can not be handled I guess}

Remarl: The static proc binlog is never used.

3.) fix the typo in the help string

proc decision(poly f)
" USAGE: decission(f);     <-- decision

4.) shouldn't Silke Spang's email adress be given at AUTHOR field ?

[seelisch]

Thanks for letting us know. Could you please check out, modify the lib and check in again? Best regards from the SINGULAR team

[hannes]

The real solution would be the use of ringlist, but for the moment the proposed changes (from the forum) are used.