Absolute value of a double in C++23

float_bitwise.cpp

#include <cmath>
#include <cstdint>
#include <cstdio>
#include <iomanip>
#include <iostream>

constexpr uint64_t mask = 0x7fffffffffffffff;
constexpr double   d1   = -3.1415926;

void print(double (&func)(double), double x) {
    // std::cout << "-----------------------" << std::endl;
    std::cout << std::fixed << std::setprecision(8) << func(x) << std::endl;
    std::cout << "-----------------------" << std::endl;
}

double c_dynamic_cast(double x) {
    return (double) (((uint64_t) x) & mask);
}

double cpp_static_cast(double x) {
    return static_cast<double>(static_cast<uint64_t>(x) & mask);
}

double ptr_cast_fabs(double x) {
    return *(double *) (*(uint64_t *) (&x) &= mask, &x);
}

double reinterprete_cast_fabs(double x) {
    return *reinterpret_cast<double *>(*reinterpret_cast<uint64_t *>(&x) &= mask, &x);
}

double type_pun_fabs(double x) {
    union {
        uint64_t i;
        double   d;
    } u;
    u.d = x;
    u.i &= mask;
    return u.d;
}

auto main() -> int {
    std::cout << "Failed Situation: data loss and complement format dislay" << '\n';
    std::cout << "c_dynamic_cast:" << '\n';
    print(c_dynamic_cast, d1);
    std::cout << "cpp_static_cast:" << '\n';
    print(cpp_static_cast, d1);
    std::cout << "Succeeded Situation:" << '\n';
    std::cout << "reinterprete_cast:" << '\n';
    print(reinterprete_cast_fabs, d1);
    std::cout << "ptr_cast_fabs:" << '\n';
    print(ptr_cast_fabs, d1);
    std::cout << "type_pun_fabs:" << '\n';
    print(type_pun_fabs, d1);
    std::cout << "fabs:" << '\n';
    print(fabs, d1);
    return EXIT_SUCCESS;
}