在c++中输出浮点数的二进制表示形式[复制]

Possible Duplicate:
Float to binary in C++

可能的副本:在c++中浮动到二进制。

I want to print out the binary representation of a float number in C++. Not very practical, just out of curiosity.

我想打印出一个浮点数在c++中的二进制表示。不是很实用，只是出于好奇。

The following program doesn't compile though. The reinterpret_cast fails. What kind of cast can I use so that I can do the " &(1 << i) " part?

但是下面的程序没有编译。reinterpret_cast失败。我可以用什么类型的cast来做“&(1 < I)”“部分?

#include <iostream>
using namespace std;


void toBinary(float num) {
  int numi = reinterpret_cast<int>(num);
  cout << num << " " << numi << endl;
  for (int i = 0; i < 8 * sizeof(num); i++){
    if (numi & (1<<i)) {
      cout << 1;
    } else {
      cout << 0;
    }
  }
  cout << endl << endl;
}

int main() {
  float a;
  cout << sizeof(int) << " " << sizeof(float) << endl;
  a = 13.5;
  toBinary(a);
  toBinary(13.9);
  toBinary(2 * a);
  toBinary(-a);
}

3 个解决方案

#1

There's a much easier way. Take a pointer to the float, and reinterpret_cast it to a pointer to char. Now loop through sizeof(float) and convert each char to 8 binary digits. This method works for doubles too.

有一个更简单的方法。取一个指向浮点数的指针，并将其重新解释为一个指向char的指针。现在循环通过sizeof(浮点数)并将每个字符转换为8个二进制数字。这种方法也适用于双打。

#2

Use a union. I did this code to do exactly what you want:

使用一个联盟。我做了这个代码来做你想做的:

// file floattobinary.cc
#include <string>
#include <inttypes.h> // for uint32_t
using namespace std;

void floatToBinary(float f, string& str)
{
    union { float f; uint32_t i; } u;
    u.f = f;
    str.clear();

    for (int i = 0; i < 32; i++)
    {
        if (u.i % 2)  str.push_back('1');
        else str.push_back('0');
        u.i >>= 1;
    }

    // Reverse the string since now it's backwards
    string temp(str.rbegin(), str.rend());
    str = temp;
}

Below is a test program to run this function:

下面是运行这个函数的测试程序:

// file test.cc
#include <iostream>
#include <string>
#include <cstdlib> // for atof(3)

using namespace std;

void floatToBinary(float, string&);

int main(int argc, const char* argv[])
{
    string str;
    float f;
    if (argc > 1)
    {
        f = static_cast<float>(atof(argv[1]));
        floatToBinary(f, str);
    }
    cout << str << endl;
    return 0;
}

Compile and run (I'm using GNU g++ on Linux):

编译和运行(我在Linux上使用GNU g++):

me@mypc:~/college/c++/utils$ g++ -c floattobinary.cc
me@mypc:~/college/c++/utils$ g++ -c test.cc
me@mypc:~/college/c++/utils$ g++ -o test *.o
me@mypc:~/college/c++/utils$ ls
floattobinary.cc  floattobinary.o  test*  test.cc  test.o
me@mypc:~/college/c++/utils$ ./test 37.73
01000010000101101110101110000101
me@mypc:~/college/c++/utils$ ./test 2.0
01000000000000000000000000000000
me@mypc:~/college/c++/utils$ ./test 0.0
00000000000000000000000000000000
me@mypc:~/college/c++/utils$ ./test 237.74
01000011011011011011110101110001
me@mypc:~/college/c++/utils$ ./test 2.74e12
01010100000111110111110100101111
me@mypc:~/college/c++/utils$ ./test 2.74e13
01010101110001110101110001111010
me@mypc:~/college/c++/utils$ ./test -88.37
11000010101100001011110101110001

#3

http://www.java2s.com/Tutorial/Cpp/0100__Development/Usingreinterpretcastcastfloattoint.htm

#1

#2