/*------------------------------------------------------*
 | Author: Maurizio Loreti, aka MLO or (HAM) I3NOO      |
 | Work:   University of Padova - Department of Physics |
 |         Via F. Marzolo, 8 - 35131 PADOVA - Italy     |
 | Phone:  +39 (049) 827-7216   FAX: +39 (049) 827-7102 |
 | EMail:  loreti@pd.infn.it                            |
 | WWW:    http://www.pd.infn.it/~loreti/mlo.html       |
 *------------------------------------------------------*

 BInary Number Encoder; the main program asks for double
 values to be translated into a signed binary number.
 Exit with EOF.

 *------------------------------------------------------*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <float.h>

#define BUFFER_LENGTH 128

void bine(double, char *);

int main() {
  for (;;) {
    char    inbuf[BUFFER_LENGTH];
    char    outbuf[BUFFER_LENGTH];
    char   *pc;
    double  value;

    fputs("? ", stdout);
    if (fgets(inbuf, BUFFER_LENGTH, stdin) == 0) break;
    if ((pc = strrchr(inbuf, '\n')) != 0) *pc = '\0';
    value = strtod(inbuf, &pc);
    if (*pc != '\0'   &&   !isspace(*pc)) {
      printf("\"%s\": invalid input\n", inbuf);
    } else {
      bine(value, outbuf);
      printf("%f --> %s binary\n", value, outbuf);
    }
  }
  puts("");
  return 0;
}

void bine(
  double  value,
  char   *out
) {

/**
 | Translates "value" into a signed binary representation, up to a
 | maximum of DBL_MANT_DIG binary digits.
**/

  unsigned long integer_part;
  unsigned int  digits = 0;

  if (value < 0) {
    value = -value;
    *out++ = '-';
  }

  if ((integer_part = value) != 0) {
    char  tempbuf[BUFFER_LENGTH];
    char *pc;

    value -= integer_part;

    for (pc = tempbuf;   integer_part;   integer_part >>= 1) {
      if (integer_part & 1) *pc++ = '1';
      else                  *pc++ = '0';
      ++digits;
    }

    do {
      *out++ = *(--pc);
    } while (pc != tempbuf);
  } else {
    *out++ = '0';
  }

  if (value != 0.0) {
    *out++ = '.';

    while (digits < DBL_MANT_DIG   &&   value != 0.0) {
      integer_part = (value *= 2.0);
      if (integer_part) {
        *out++ = '1';
        value -= 1.0;
      } else {
        *out++ = '0';
      }
      ++digits;
    }
  }

  *out = '\0';
}