Playing with floats: bits to floats and floats to bits.

bits2float.cc

#include "showbits.h"

#include <iostream>
#include <algorithm>
#include <string>
#include <locale>
#include <cassert>

typedef union {
    int64_t i;
    double f;
} i2f64_t;

typedef union {
    int32_t i;
    float f;
} i2f32_t;

void trim(std::string& s) {
  s.erase(std::remove_if(
        begin(s), end(s),
        [l = std::locale{}](auto ch) { return std::isspace(ch, l); }
        ), end(s));
}

template <class T>
T mystoi(std::string s) {
  if (s[0] == '1') {
    s[0] = '0';
    T num = std::stoi(s, nullptr, 2);
    return num - (1 << (sizeof(T)*8-1));
  } else {
    return std::stoi(s, nullptr, 2);
  }
}

int main(int argc, char* argv[])
{
  if (argc < 2) {
    printf("usage: %s, -d <double_number> or -f <float_number>\n", argv[0]);
    exit(1);
  }
  if (strcmp(argv[1], "-d") == 0) {
    for (int i = 2; i < argc; ++i) {
      std::string input = argv[i];
      trim(input);
      assert(input.size() == 64);
      i2f64_t number = {.i = mystoi<int64_t>(input)};
      printBits(sizeof(int64_t), &number);
      printf("%lf\n", number.f);
    }
  } else if (strcmp(argv[1], "-f") == 0) {
    for (int i = 2; i < argc; ++i) {
      std::string input = argv[i];
      trim(input);
      assert(input.size() == 32);
      i2f32_t number = {.i = mystoi<int32_t>(input)};
      printBits(sizeof(int32_t), &number);
      printf("%f\n", number.f);
    }
  } else {
    printf("usage: %s, -d <double_number> or -f <float_number>\n", argv[0]);
    exit(1);
  }
}

float2bits.c

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

#include "showbits.h"

int main(int argc, char* argv[])
{
  if (argc < 2) {
    printf("usage: %s, -d <double_number> or -f <float_number>\n", argv[0]);
    exit(1);
  }
  if (strcmp(argv[1], "-d") == 0) {
    if (argc == 2) {
      printf("DBL_MIN: %lf\n", DBL_MIN);
      double dblmin = DBL_MIN;
      printBits(sizeof(float), &dblmin);
      printf("DBL_MAX: %lf\n", DBL_MAX);
      double dblmax = DBL_MAX;
      printBits(sizeof(float), &dblmax);
    } else {
      for (int i = 2; i < argc; ++i) {
        double input = strtod(argv[i], NULL);
        printBits(sizeof(double), &input);
      }
    }
  } else if (strcmp(argv[1], "-f") == 0) {
    if (argc == 2) {
      printf("FLT_MIN: %f\n", FLT_MIN);
      float fltmin = FLT_MIN;
      printBits(sizeof(float), &fltmin);
      printf("FLT_MAX: %f\n", FLT_MAX);
      float fltmax = FLT_MAX;
      printBits(sizeof(float), &fltmax);
    } else {
      for (int i = 2; i < argc; ++i) {
        float input = atof(argv[i]);
        printBits(sizeof(float), &input);
      }
    }
  } else {
    printf("usage: %s, -d <double_number> or -f <float_number>\n", argv[0]);
    exit(1);
  }
}

format.py

#!/usr/bin/env python3

import sys

bitstring = input()
del_pos = int(sys.argv[1])
while bitstring:
    print(bitstring[:1]+' '+bitstring[1:del_pos]+' '+bitstring[del_pos:])
    bitstring = input()

showbits.c

#include <stdio.h>
#include <float.h>
#include <string.h>
#include <limits.h>
#include <stdlib.h>
#include "showbits.h"

void printBits(size_t const size, void const * const ptr)
{
    unsigned char *b = (unsigned char*) ptr;
    unsigned char byte;
    int i, j;

    for (i=size-1;i>=0;i--)
    {
        for (j=7;j>=0;j--)
        {
            byte = (b[i] >> j) & 1;
            printf("%u", byte);
        }
        /*printf(" ");*/
    }
    puts("");
}

showbits.h

#ifndef _SHOWBITS_H
#define _SHOWBITS_H

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

void printBits(size_t const size, void const * const ptr);

#endif