C++ (Cpp) ComputeLn10 Examples

Example #1

File: xdouble.cpp Project: kenjinote/NTLSample

long ComputeMax10Power()
{
   RRPush push;
   RR::SetPrecision(NTL_BITS_PER_LONG);

   RR ln2, ln10;
   ComputeLn2(ln2);
   ComputeLn10(ln10);

   long k = to_long( to_RR(NTL_OVFBND/2) * ln2 / ln10 );
   return k;
}

Example #2

File: RR.c Project: Macaulay2/Singular

void log10(RR& res, const RR& x)
{
   long p = RR::precision();
   RR::SetPrecision(p + 10);

   RR ln10, t1, t2;
   ComputeLn10(ln10);

   log(t1, x);
   div(t2, t1, ln10);

   RR::SetPrecision(p);

   xcopy(res, t2);
}

Example #3

File: xdouble.cpp Project: kenjinote/NTLSample

ostream& operator<<(ostream& s, const xdouble& a)
{
   if (a == 0) {
      s << "0";
      return s;
   }

   RRPush push;
   long temp_p = long(log(fabs(log(fabs(a))) + 1.0)/log(2.0)) + 10; 
   RR::SetPrecision(temp_p);

   RR ln2, ln10, log_2_10;
   ComputeLn2(ln2);
   ComputeLn10(ln10);
   log_2_10 = ln10/ln2;
   ZZ log_10_a = to_ZZ(
  (to_RR(a.e)*to_RR(2*NTL_XD_HBOUND_LOG) + log(fabs(a.x))/log(2.0))/log_2_10);


   xdouble b;
   long neg;

   if (a < 0) {
      b = -a;
      neg = 1;
   }
   else {
      b = a;
      neg = 0;
   }

   ZZ k = xdouble::OutputPrecision() - log_10_a;

   xdouble c, d;

   c = PowerOf10(to_ZZ(xdouble::OutputPrecision()));
   d = PowerOf10(log_10_a);

   b = b / d;
   b = b * c;

   while (b < c) {
      b = b * 10.0;
      k++;
   }

   while (b >= c) {
      b = b / 10.0;
      k--;
   }

   b = b + 0.5;
   k = -k;

   ZZ B;
   conv(B, b);

   long bp_len = xdouble::OutputPrecision()+10;

   UniqueArray<char> bp_store;
   bp_store.SetLength(bp_len);
   char *bp = bp_store.get();

   long len, i;

   len = 0;
   do {
      if (len >= bp_len) LogicError("xdouble output: buffer overflow");
      bp[len] = IntValToChar(DivRem(B, B, 10));
      len++;
   } while (B > 0);

   for (i = 0; i < len/2; i++) {
      char tmp;
      tmp = bp[i];
      bp[i] = bp[len-1-i];
      bp[len-1-i] = tmp;
   }

   i = len-1;
   while (bp[i] == '0') i--;

   k += (len-1-i);
   len = i+1;

   bp[len] = '\0';

   if (k > 3 || k < -len - 3) {
      // use scientific notation

      if (neg) s << "-";
      s << "0." << bp << "e" << (k + len);
   }
   else {
      long kk = to_long(k);

      if (kk >= 0) {
         if (neg) s << "-";
         s << bp;
         for (i = 0; i < kk; i++) 
            s << "0";
      }
      else if (kk <= -len) {
         if (neg) s << "-";
         s << "0.";
         for (i = 0; i < -len-kk; i++)
            s << "0";
         s << bp;
      }
      else {
         if (neg) s << "-";
         for (i = 0; i < len+kk; i++)
            s << bp[i];
   
         s << ".";
   
         for (i = len+kk; i < len; i++)
            s << bp[i];
      }
   }

   return s;
}