Examples of std::variant
Let’s illustrate the std::variant with some code examples.
Example 1
C++
// C++ Program to illustrate std::variant #include <iostream> #include <string> #include <variant> using namespace std; int main() { variant<int, double, string> myVariant; myVariant = 42; // Assign an int // Access the int if (holds_alternative<int>(myVariant)) { cout << get<int>(myVariant) << endl; } myVariant = 3.14; // Assign a double // Access the double if (holds_alternative<double>(myVariant)) { cout << get<double>(myVariant) << endl; } myVariant = "Hello, Variant!"; // Assign a string // Access the string if (holds_alternative<string>(myVariant)) { cout << get<string>(myVariant) << endl; } return 0; } |
Output
42 3.14 Hello, Variant!
Example 2
C++
// C++ Program to illustrate std::variant #include <iostream> #include <variant> using namespace std; // Define custom data types struct Circle { double radius; }; struct Square { double side; }; // driver code int main() { variant<Circle, Square> shapeVariant; // Create a Circle shapeVariant = Circle{ 5.0 }; // Check the active type and perform operations // accordingly if (holds_alternative<Circle>(shapeVariant)) { Circle c = get<Circle>(shapeVariant); cout << "Circle with radius: " << c.radius << endl; } else if (holds_alternative<Square>(shapeVariant)) { Square s = get<Square>(shapeVariant); cout << "Square with side: " << s.side << endl; } else { // Handle the case where the variant does not // contain either a Circle or a Square cout << "Unrecognized shape" << endl; } return 0; } |
Output
Circle with radius: 5
std::variant in C++ 17
In the world of modern C++ programming, the std::variant is a powerful tool that allows you to work with multiple data types in a flexible and type-safe manner. In this article, we will discuss std::variant and explore its fundamentals, applications, and benefits with practical code examples.
Prerequisites: C++ data types, functions, unions, and classes.