4.3BSD/usr/contrib/icon/rt/gcvt.c

/*
 * gcvt - Convert number to a string in buf.  If possible, ndigit significant
 *  digits are produced, otherwise a form with an exponent is used.
 */
char   *ecvt();
char *
gcvt(number, ndigit, buf)
double number;
char *buf;
   {
   int sign, decpt;
   register char *p1, *p2;
   register i;
   int junk;

   p1 = ecvt(number, ndigit, &decpt, &sign);
   p2 = buf;
   if (sign)
      *p2++ = '-';
   for (i=ndigit-1; i>0 && p1[i]=='0'; i--)
      ndigit--;
   if (decpt >= 0 && decpt-ndigit > 4
      || decpt < 0 && decpt < -3) { /* use E-style */
         decpt--;
         *p2++ = *p1++;
         *p2++ = '.';
         for (i=1; i<ndigit; i++)
            *p2++ = *p1++;
         *p2++ = 'e';
         if (decpt<0) {
            decpt = -decpt;
            *p2++ = '-';
            }
         if (decpt/10 > 0)
            *p2++ = decpt/10 + '0';
         *p2++ = decpt%10 + '0';
      } else {
         if (decpt<=0) {
         /* if (*p1!='0') */
         *p2++ = '0';
         *p2++ = '.';
         while (decpt<0) {
            decpt++;
            *p2++ = '0';
            }
         }
         for (i=1; i<=ndigit; i++) {
            *p2++ = *p1++;
            if (i==decpt)
               *p2++ = '.';
            }
      if (ndigit<decpt) {
         while (ndigit++<decpt)
            *p2++ = '0';
         *p2++ = '.';
         }
   }
   if (p2[-1]=='.')
      *p2++ = '0';
   *p2 = '\0';
   return(buf);
   }