Adding a IEEE-754 Floating Point and a Float number in C++

Question

I have two variables.

variable_1 = 01000001000011110101110000101001(0x410f5c29 in IEEE-754 Floating Point format) which is 8.96 in Decimal.

float variable_2 = 0.2 

I want to add them like

float variable_3 = variable_1 + variable_2; // in C++

I just need to know how will I assign them to variables so that they are taken what they are. This will include declaring variable_1 and assiging it the value.

Answer 1

Set an unsigned integer to the desired bits and use std::memcpy to copy them into a float:

#include <cstdint>
#include <cstring>
#include <iomanip>
#include <iostream>
#include <limits>


int main()
{
    uint32_t au = 0x410f5c29;
    float    a;

    static_assert(sizeof (float) == sizeof (uint32_t),
        "sizes of float and uint32_t must be the same");
    std::memcpy(&a, &au, sizeof a);

    float    b  = .2;
    float    c  = a+b;

    std::cout << std::setprecision(99);
    std::cout << "a = " << a << ".\n";
    std::cout << "b = " << b << ".\n";
    std::cout << "c = " << c << ".\n";
}

Sample output:

a = 8.96000003814697265625.
b = 0.20000000298023223876953125.
c = 9.159999847412109375.