Bell 32V development

[unix-history] / usr / src / libc / gen / modf.c

double
modf(arg,ent)
double arg;
double *ent;
{
       int neg;
       int i;
       double two30 = 1073741824.;
       double big = 72057594037927936.;  /*2^56*/
       double x, temp;
       double ldexp();
       double frexp();
       long l;

       neg = 1;
       if(arg<0){
               neg = -1;
               arg = -arg;
               }
       if(arg>big){
               *ent = neg*arg;
               return(0);
               }
       if(arg<1){
               *ent = 0;
               return(neg*arg);
               }

       temp = 0;
       while(arg>two30){
               x = frexp(arg,&i);
               if(arg<0.5){
                       arg = 2*arg;
                       i = i-1;
                       }
               x = ldexp(0.5,i);
               arg = arg - x;
               temp = temp + x;
               }

       l = arg;
       arg = arg-l;
       temp = temp+l;
       *ent = neg*temp;
       return(neg*arg);
       }