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Absolute value of a double in C++23
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#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; | |
} |
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