ieee754

https://www.zhihu.com/question/21711083

 

https://www.jianshu.com/p/cb377fd1a295

 

 

#include <iostream>
#include "string"
using namespace std;
#include "math.h"

/*IEEE754
31   30..23   22..0
S | E + 127 | M 1.*
-0.75 -> bf400000
 float  1 | 8 | 23
 double 1 | 11| 52
 */



int cmain() {
    unsigned int a1 = 0xff900000;
    float a2 = *(float *)&a1;
    a2 = INFINITY;
    int ar = isfinite(a2);
    int sb = signbit(a2);
    int rb = fpclassify(a2);
    int rc = isnormal(a2);
    printf("%f\n", a2);
    float d = -0.75;
    int *p = (int *)&d;
    printf("%x\n", *p);
    auto s = std::to_string(9.8);
    printf("%03.3lf\n", 9.87876);
    printf("%8d\n", 123456);
    std::cout << s << std::endl;
    return 0;
}

 

 

 

 

https://blog.csdn.net/linuxheik/article/details/78497649

int32_t float2int(double d){
    union {double f; int32_t i;} u = {d};
    u.f += 6755399441055744.0; //0x1.8p52; // 1.5 * 2^52
    return u.i;
}