C++ STL的std :: is_signed模板用于检查类型是否为带符号算术类型。
语法:
template struct is_signed;
参数:该模板包含单个参数T(Trait类),以检查T是否为带符号算术类型。
返回值:该模板返回一个布尔值,如下所示:
- True :如果类型是带符号的算术类型。
- False :如果类型是无符号算术类型。
下面的程序说明了C++ STL中的std :: is_signed模板:
程序1 :
// C++ program to illustrate
// std::is_signed template
#include
#include
using namespace std;
class gfg {
};
enum sam : int {};
enum class raj : int {};
int main()
{
cout << boolalpha;
cout << "is_signed:" << '\n';
cout << "int:" << is_signed::value << '\n';
cout << "gfg:" << is_signed::value << '\n';
cout << "sam:" << is_signed::value << '\n';
cout << "raj:" << is_signed::value << '\n';
return 0;
}
输出:
is_signed:
int:true
gfg:false
sam:false
raj:false
程序2 :
// C++ program to illustrate
// std::is_signed template
#include
#include
using namespace std;
int main()
{
cout << boolalpha;
cout << "is_signed:" << '\n';
cout << "float:"
<< is_signed::value << '\n';
cout << "signed int:"
<< is_signed::value << '\n';
cout << "unsigned int:"
<< is_signed::value << '\n';
return 0;
}
输出:
is_signed:
float:true
signed int:true
unsigned int:false
程序3 :
// C++ program to illustrate
// std::is_signed template
#include
#include
using namespace std;
int main()
{
cout << boolalpha;
cout << "is_signed:" << '\n';
cout << "bool:" << is_signed::value << '\n';
cout << "unsigned char:"
<< is_signed::value << '\n';
cout << "signed char:"
<< is_signed::value << '\n';
cout << "double:"
<< is_signed::value << '\n';
return 0;
}
输出:
is_signed:
bool:false
unsigned char:false
signed char:true
double:true
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