UNIX 6th Ed. - /usr/source/iolib/ftoa.c

   1: ftoa (x, str, prec, format)
   2: float x;
   3: char *str;
   4: {
   5: /* converts a floating point number to an ascii string */
   6: /* x is stored into str, which should be at least 30 chars long */
   7: int ie, i, k, ndig, fstyle;
   8: double y;
   9: if (nargs() != 7)
  10:   IEHzap("ftoa  ");
  11: ndig = ( prec<=0) ? 7 : (prec > 22 ? 23 : prec+1);
  12: if  (format == 'f' || format == 'F')
  13:  fstyle = 1;
  14: else
  15:  fstyle = 0;
  16: /* print in e format unless last arg is 'f' */
  17: ie = 0;
  18: /* if x negative, write minus and reverse */
  19: if ( x < 0)
  20:   {
  21:   *str++ = '-';
  22:   x = -x;
  23:   }
  24: 
  25: /* put x in range 1 <= x < 10 */
  26: if (x > 0.0) while (x < 1.0)
  27:   {
  28:   x =* 10.0;
  29:   ie--;
  30:   }
  31: while (x >= 10.0)
  32:   {
  33:   x = x/10.0;
  34:   ie++;
  35:   }
  36: 
  37: /* in f format, number of digits is related to size */
  38: if (fstyle) ndig =+ ie;
  39: 
  40: /* round. x is between 1 and 10 and ndig will be printed to
  41:    right of decimal point so rounding is ... */
  42: for (y = i = 1; i < ndig; i++)
  43:   y = y/10.;
  44: x =+ y/2.;
  45: if (x >= 10.0) {x = 1.0; ie++;} /* repair rounding disasters */
  46: /* now loop.  put out a digit (obtain by multiplying by
  47:   10, truncating, subtracting) until enough digits out */
  48: /* if fstyle, and leading zeros, they go out special */
  49: if (fstyle && ie<0)
  50:   {
  51:   *str++ = '0'; *str++ = '.';
  52:   if (ndig < 0) ie = ie-ndig; /* limit zeros if underflow */
  53:   for (i = -1; i > ie; i--)
  54:     *str++ = '0';
  55:   }
  56: for (i=0; i < ndig; i++)
  57:   {
  58:   k = x;
  59:   *str++ = k + '0';
  60:   if (i == (fstyle ? ie : 0)) /* where is decimal point */
  61:     *str++ = '.';
  62:   x =- (y=k);
  63:   x =* 10.0;
  64:   }
  65: 
  66: /* now, in estyle,  put out exponent if not zero */
  67: if (!fstyle && ie != 0)
  68:   {
  69:   *str++ = 'E';
  70:   if (ie < 0)
  71:     {
  72:     ie = -ie;
  73:     *str++ = '-';
  74:     }
  75:   for (k=100; k > ie; k =/10);
  76:   for (; k > 0; k =/10)
  77:        {
  78:        *str++ = ie/k + '0';
  79:        ie = ie%k;
  80:        }
  81:   }
  82: *str = '\0';
  83: return;
  84: }

Defined functions