Switch in C++

Here’s an example of how to use switch statements to handle multiple conditions across different branches.

#include <iostream>
#include <ctime>

int main() {
    // Basic switch statement
    int i = 2;
    std::cout << "Write " << i << " as ";
    switch (i) {
        case 1:
            std::cout << "one" << std::endl;
            break;
        case 2:
            std::cout << "two" << std::endl;
            break;
        case 3:
            std::cout << "three" << std::endl;
            break;
    }

    // Switch with multiple expressions in the same case and default case
    std::time_t now = std::time(0);
    std::tm *ltm = std::localtime(&now);
    switch (ltm->tm_wday) {
        case 0: // Sunday
        case 6: // Saturday
            std::cout << "It's the weekend" << std::endl;
            break;
        default:
            std::cout << "It's a weekday" << std::endl;
            break;
    }

    // Switch without an expression to mimic if-else logic
    int hour = ltm->tm_hour;
    switch (true) {
        case true:
            if (hour < 12) {
                std::cout << "It's before noon" << std::endl;
            } else {
                std::cout << "It's after noon" << std::endl;
            }
            break;
    }
    
    // Type switch example (using templates and function overloading in C++)
    auto whatAmI = [](auto i) {
        if constexpr (std::is_same_v<decltype(i), bool>) {
            std::cout << "I'm a bool" << std::endl;
        } else if constexpr (std::is_same_v<decltype(i), int>) {
            std::cout << "I'm an int" << std::endl;
        } else {
            std::cout << "Don't know type " << typeid(i).name() << std::endl;
        }
    };

    whatAmI(true);
    whatAmI(1);
    whatAmI("hey");
    
    return 0;
}

To run the program, ensure you have a C++ compiler like g++ installed. Save the code to a file named switch.cpp, compile it, and run the resulting executable:

$ g++ -o switch_example switch.cpp
$ ./switch_example
Write 2 as two
It's a weekday
It's after noon
I'm a bool
I'm an int
Don't know type PKc

In this example, the C++ code demonstrates the use of switch statements with integral values, multiple case expressions, default cases, and emulating type switching with function templates. Note that C++ doesn’t have a built-in type switch, but we can achieve similar behavior using templates and function overloading.

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Switch in C++