C++函数对象-运算符函数对象 - 逻辑运算 - 实现 !x 的函数对象 （std::logical_not）

C++ 针对常用的算术和逻辑运算定义了很多函数对象：

逻辑运算

实现 !x 的函数对象

std::logical_not

实现逻辑非（逻辑取反）的函数对象。等效地调用类型 T 的 operator! 。

特化

成员函数

调用示例

#include <iostream>
#include <functional>struct Cell
{int x;int y;Cell() = default;Cell(int a, int b): x(a), y(b) {}Cell(const Cell &cell){x = cell.x;y = cell.y;}Cell &operator+(const Cell &cell){x += cell.x;y += cell.y;return *this;}Cell &operator+=(const Cell &cell){x += cell.x;y += cell.y;return *this;}Cell &operator*=(int n){x *= n;y *= n;return *this;}Cell &operator++(){x += 1;y += 1;return *this;}friend Cell operator +(const Cell &cell1, const Cell &cell2){Cell cell = cell1;cell += cell2;return cell;}friend Cell operator *(const Cell &cell1, const Cell &cell2){Cell cell = {cell1.x * cell2.x, cell1.y * cell2.y};return cell;}friend Cell operator /(const Cell &cell1, const Cell &cell2){Cell cell = {cell1.x / cell2.x, cell1.y / cell2.y};return cell;}friend Cell operator %(const Cell &cell1, const Cell &cell2){Cell cell = {cell1.x % cell2.x, cell1.y % cell2.y};return cell;}friend bool operator ==(const Cell &cell1, const Cell &cell2){return cell1.x == cell2.x && cell1.y == cell2.y;}friend bool operator !=(const Cell &cell1, const Cell &cell2){return cell1.x != cell2.x && cell1.y != cell2.y;}friend bool operator <(const Cell &cell1, const Cell &cell2){if (cell1.x == cell2.x){return cell1.y < cell2.y;}else{return cell1.x < cell2.x;}}friend bool operator >(const Cell &cell1, const Cell &cell2){if (cell1.x == cell2.x){return cell1.y > cell2.y;}else{return cell1.x > cell2.x;}}friend bool operator &&(const Cell &cell1, const Cell &cell2){return cell1.x && cell2.x && cell1.y && cell2.y;}friend bool operator ||(const Cell &cell1, const Cell &cell2){return cell1.x || cell2.x || cell1.y || cell2.y;}friend bool operator !(const Cell &cell){return !(cell.x && cell.x);}
};std::ostream &operator<<(std::ostream &os, const Cell &cell)
{os << "{" << cell.x << "," << cell.y << "}";return os;
}int main()
{std::cout << std::boolalpha;int *ptr = nullptr;std::cout << "std::logical_not<int*>()(ptr, nullptr):   "<< std::logical_not<int*>()(ptr) << std::endl;std::cout << "std::logical_not<char>()(50):             "<< std::logical_not<char>()(50) << std::endl;std::cout << "std::logical_not<char>()('a'):            "<< std::logical_not<char>()('a') << std::endl;std::cout << "std::logical_not<int>()(1023):            "<< std::logical_not<int>()(1023) << std::endl;std::cout << "std::logical_not<long>()(1023):           "<< std::logical_not<long>()(1023) << std::endl;std::cout << "std::logical_not<long long>()(1023):      "<< std::logical_not<long long>()(1023) << std::endl;std::cout << "std::logical_not<uint8_t>()(1023):        "<< std::logical_not<uint8_t>()(8) << std::endl;std::cout << "std::logical_not<uint16_t>()(123):        "<< std::logical_not<uint16_t>()(123) << std::endl;std::cout << "std::logical_not<uint32_t>()(101):        "<< std::logical_not<uint32_t>()(101) << std::endl;std::cout << "std::logical_not<uint64_t>()(10230):      "<< std::logical_not<uint64_t>()(10230) << std::endl;std::cout << "std::logical_not<int8_t>()(1023):         "<< std::logical_not<int8_t>()(8) << std::endl;std::cout << "std::logical_not<int16_t>()(123):         "<< std::logical_not<int16_t>()(123) << std::endl;std::cout << "std::logical_not<int32_t>()(101):         "<< std::logical_not<int32_t>()(101) << std::endl;std::cout << "std::logical_not<int64_t>()(10230):       "<< std::logical_not<int64_t>()(10230) << std::endl;std::cout << "std::logical_not<double>()(3.14):         "<< std::logical_not<double>()(3.14) << std::endl;std::cout << "std::logical_not<float>()(3.14):          "<< std::logical_not<float>()(3.14) << std::endl;std::cout << "std::logical_not<float>()(3):             "<< std::logical_not<float>()(3) << std::endl;std::cout << "std::logical_not<float>()(3.56):          "<< std::logical_not<float>()(3.56) << std::endl;std::cout << "std::logical_not<int>()(3.14):            "<< std::logical_not<int>()(3.34) << std::endl;std::cout << "std::logical_not<Cell>()(Cell{101, 101}): "<< std::logical_not<Cell>()(Cell{101, 101}) << std::endl;std::cout << "std::logical_not<Cell>()(Cell{0, 0}):     "<< std::logical_not<Cell>()(Cell{0, 0}) << std::endl;//编译失败
//    std::cout << "std::logical_not<std::string>()(\"I am a handsome programmer\"):"
//              << std::logical_not<std::string>()("I am a handsome programmer") << std::endl;return 0;
}

输出

std::logical_not<int*>()(ptr, nullptr):   true
std::logical_not<char>()(50):             false
std::logical_not<char>()('a'):            false
std::logical_not<int>()(1023):            false
std::logical_not<long>()(1023):           false
std::logical_not<long long>()(1023):      false
std::logical_not<uint8_t>()(1023):        false
std::logical_not<uint16_t>()(123):        false
std::logical_not<uint32_t>()(101):        false
std::logical_not<uint64_t>()(10230):      false
std::logical_not<int8_t>()(1023):         false
std::logical_not<int16_t>()(123):         false
std::logical_not<int32_t>()(101):         false
std::logical_not<int64_t>()(10230):       false
std::logical_not<double>()(3.14):         false
std::logical_not<float>()(3.14):          false
std::logical_not<float>()(3):             false
std::logical_not<float>()(3.56):          false
std::logical_not<int>()(3.14):            false
std::logical_not<Cell>()(Cell{101, 101}): false
std::logical_not<Cell>()(Cell{0, 0}):     true