通过int 关系运算符来 比较两个 float 变量的大小

#include <stdio.h>
#include <iostream>
#include <random>

using namespace std;

void compare_unnegative_float();
void show_details();

union float_int_type{
    unsigned    m_unsigned;    
    float       m_float;
    struct{
        unsigned     m_significand  : 23;
        unsigned     m_exponent  :  8;
        bool    m_sign :  1;
    };
};

constexpr int FLOAT_MIN = 0;
constexpr int FLOAT_MAX = 10;
int main(){

    union float_int_type x, y;

    x.m_float = 0.0f;
    printf("%x, %f, %u, %u, %u\n",x.m_unsigned, x.m_float, x.m_significand, x.m_exponent, x.m_sign);
    cout  << x.m_float <<":   exponent="<<x.m_exponent<<"        significand="<<x.m_significand<<endl;

    std::random_device rd;
    std::default_random_engine eng(rd());
    std::uniform_real_distribution<float> distr(FLOAT_MIN, FLOAT_MAX);

    compare_unnegative_float();

    //show_details();

    return 0;
}


void compare_non_negative_float(){

    union float_int_type x, y;

    x.m_float = 0.0f;
    printf("%x, %f, %u, %u, %u\n",x.m_unsigned, x.m_float, x.m_significand, x.m_exponent, x.m_sign);
    cout  << x.m_float <<":   exponent="<<x.m_exponent<<"        significand="<<x.m_significand<<endl;

    std::random_device rd;
    std::default_random_engine eng(rd());
    std::uniform_real_distribution<float> distr(FLOAT_MIN, FLOAT_MAX);

    for(unsigned i=0; i<-1; i++){
        if(i%10000000==0) cout<<i<<endl;

        x.m_float = distr(eng);
        y.m_float = distr(eng);
        if(x.m_exponent>y.m_exponent || (x.m_exponent==y.m_exponent && x.m_significand>y.m_significand))
        {
            if(!(x.m_float> y.m_float)) cout<<"Error: "<<x.m_float<<" > "<<y.m_float<<" is false!"<<endl;
        }else if(x.m_exponent < y.m_exponent || (x.m_exponent == y.m_exponent && x.m_significand<y.m_significand))
        {
            if(!(x.m_float < y.m_float)) cout<<"Error: "<<x.m_float<<" < "<<y.m_float<<" is false!"<<endl;
        }else
        {
            if(!(x.m_float == y.m_float)) cout<<"Error: "<<x.m_float<<" == "<<y.m_float<<" is false!"<<endl;
        }
    }
}



void show_details(){

    union float_int_type x;
    x.m_float = 1.0f;
    printf("%x, %f, %u, %u, %u\n",x.m_unsigned, x.m_float, x.m_significand, x.m_exponent, x.m_sign);
    cout  << x.m_float <<":   exponent="<<x.m_exponent<<"        significand="<<x.m_significand<<endl;

    std::random_device rd;
    std::default_random_engine eng(rd());
    std::uniform_real_distribution<float> distr(FLOAT_MIN, FLOAT_MAX);

    for(int i=0; i<100; i++){
        if(i%10==0) cout<<endl;
        x.m_float = distr(eng);
        cout  << x.m_float <<":   exponent="<<x.m_exponent<<"        significand="<<x.m_significand<<endl;
    }
    cout <<endl;
}