<type_traits>

类模板
<type_traits>

std::is_scalar

template <class T> struct is_scalar;
Is scalar type

Trait class that identifies whether T is a scalar type. A scalar type is a type that has built-in functionality for the addition operator without overloads (arithmetic, pointer, member pointer, enum andstd::nullptr_t).

它继承自 integral_constant,并根据Tis a scalar type, no matter its const and/or volative qualification.

这是一个复合类型特征,其行为与以下代码相同:
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template<class T>
struct is_scalar : std::integral_constant < bool,
         is_arithmetic<T>::value || is_pointer<T>::value ||
         is_member_pointer<T>::value || is_enum<T>::value ||
         is_same<nullptr_t, typename remove_cv<T>::type>::value> {};

模板参数

T
一个类型。

成员类型

Inherited from integral_constant
成员类型定义
value_typebool
类型true_type 或 false_type

成员常量

Inherited from integral_constant
成员常量定义
trueorfalse

成员函数

Inherited from integral_constant

示例

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// is_scalar example
#include <iostream>
#include <type_traits>

class A {};

int main() {
  std::cout << std::boolalpha;
  std::cout << "is_scalar:" << std::endl;
  std::cout << "int: " << std::is_scalar<int>::value << std::endl;
  std::cout << "A: " << std::is_scalar<A>::value << std::endl;
  std::cout << "A&: " << std::is_scalar<A&>::value << std::endl;
  std::cout << "A*: " << std::is_scalar<A*>::value << std::endl;
  std::cout << "int(int): " << std::is_scalar<int(int)>::value << std::endl;
  std::cout << "int(*)(int): " << std::is_scalar<int(*)(int)>::value << std::endl;
  return 0;
}

输出
is_scalar:
int: true
A: false
A&: false
A*: true
int(int): false
int(*)(int): true


另见