Różnica między char a signed char w c ++?
Rozważ następujący kod:
#include <iostream>
#include <type_traits>
int main(int argc, char* argv[])
{
std::cout<<"std::is_same<int, int>::value = "<<std::is_same<int, int>::value<<std::endl;
std::cout<<"std::is_same<int, signed int>::value = "<<std::is_same<int, signed int>::value<<std::endl;
std::cout<<"std::is_same<int, unsigned int>::value = "<<std::is_same<int, unsigned int>::value<<std::endl;
std::cout<<"std::is_same<signed int, int>::value = "<<std::is_same<signed int, int>::value<<std::endl;
std::cout<<"std::is_same<signed int, signed int>::value = "<<std::is_same<signed int, signed int>::value<<std::endl;
std::cout<<"std::is_same<signed int, unsigned int>::value = "<<std::is_same<signed int, unsigned int>::value<<std::endl;
std::cout<<"std::is_same<unsigned int, int>::value = "<<std::is_same<unsigned int, int>::value<<std::endl;
std::cout<<"std::is_same<unsigned int, signed int>::value = "<<std::is_same<unsigned int, signed int>::value<<std::endl;
std::cout<<"std::is_same<unsigned int, unsigned int>::value = "<<std::is_same<unsigned int, unsigned int>::value<<std::endl;
std::cout<<"----"<<std::endl;
std::cout<<"std::is_same<char, char>::value = "<<std::is_same<char, char>::value<<std::endl;
std::cout<<"std::is_same<char, signed char>::value = "<<std::is_same<char, signed char>::value<<std::endl;
std::cout<<"std::is_same<char, unsigned char>::value = "<<std::is_same<char, unsigned char>::value<<std::endl;
std::cout<<"std::is_same<signed char, char>::value = "<<std::is_same<signed char, char>::value<<std::endl;
std::cout<<"std::is_same<signed char, signed char>::value = "<<std::is_same<signed char, signed char>::value<<std::endl;
std::cout<<"std::is_same<signed char, unsigned char>::value = "<<std::is_same<signed char, unsigned char>::value<<std::endl;
std::cout<<"std::is_same<unsigned char, char>::value = "<<std::is_same<unsigned char, char>::value<<std::endl;
std::cout<<"std::is_same<unsigned char, signed char>::value = "<<std::is_same<unsigned char, signed char>::value<<std::endl;
std::cout<<"std::is_same<unsigned char, unsigned char>::value = "<<std::is_same<unsigned char, unsigned char>::value<<std::endl;
return 0;
}
Wynik to :
std::is_same<int, int>::value = 1
std::is_same<int, signed int>::value = 1
std::is_same<int, unsigned int>::value = 0
std::is_same<signed int, int>::value = 1
std::is_same<signed int, signed int>::value = 1
std::is_same<signed int, unsigned int>::value = 0
std::is_same<unsigned int, int>::value = 0
std::is_same<unsigned int, signed int>::value = 0
std::is_same<unsigned int, unsigned int>::value = 1
----
std::is_same<char, char>::value = 1
std::is_same<char, signed char>::value = 0
std::is_same<char, unsigned char>::value = 0
std::is_same<signed char, char>::value = 0
std::is_same<signed char, signed char>::value = 1
std::is_same<signed char, unsigned char>::value = 0
std::is_same<unsigned char, char>::value = 0
std::is_same<unsigned char, signed char>::value = 0
std::is_same<unsigned char, unsigned char>::value = 1
Co oznacza żeint
isigned int
są uważane za ten sam typ, ale niechar
isigned char
. Dlaczego ?
A jeśli potrafię przekształcićchar
wsigned char
za pomocąmake_signed
, jak zrobić przeciwieństwo (przekształć asigned char
do achar
)?