smallestpower()

int datrw::su::ScalCoo::smallestpower

(

const short &

desiredscale = datrw::su::subformat::def::scalco

)

const

smallest possible power larger or equal desired

return smallest power possible without truncation

Definition at line 298 of file sucomanager.cc.

References coo, power(), and datrw::su::scaletopower().

Referenced by datrw::su::Coordinates::equalizescaling(), and set().

    {
      // limiting power values
      int desired=datrw::su::scaletopower(desiredscale);
      int lp=desired >= -4 ? desired : -4;
      lp = lp <= 4 ? lp : 4;
      // initial power
      int p=this->power();
      /*
       * code modification; 24.1.2012
       * tests were previously done detecting overflow
       *
      // value and compare value
      ScalCoo v1(Mcontrol), v2(Mcontrol);
      v1.coo=this->coo;
      v2.coo=std::floor(v1.coo*10)/10;
      do {
        if ((v1.coo==v2.coo) && (p>lp))
        {
          --p;
          v1.coo *= 10;
          v2.coo=std::floor(v1.coo*10)/10;
        }
      } while ((v1.coo==v2.coo) && (p>lp));
      *
      * I prefer to use numerical comparison
      * increasing the scale power will decrease the coo value and vice versa;
      * start with the optimal power as being found in this->scale
      * decrease the power until 
      *   either a further decrease would result in coo not fitting into a
      *     variable of type short
      *   or the desired scale (scale power) value is obtained
      */
      int c1=this->coo;
      int c2;
      bool hot=true;
      do {
        if (hot && (p>lp))
        {
          --p;
          c1 *= 10;
        }
        c2=c1*10; 
        hot = ((c2 <= SHRT_MAX) && (c2 >= SHRT_MIN));
      } while (hot && (p>lp));
      return(p);
    } // int ScalCoo::smallestpower()

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