Enums in C++

Based on your input, the target language is C++. Here is the translation of the provided example in Markdown format suitable for Hugo.

Enumerated types (enums) in C++ are a special case of sum types. An enum in C++ is a type with a fixed number of possible values, each associated with a distinct name.

Our enum type ServerState is defined as follows:

#include <iostream>
#include <string>
#include <unordered_map>

enum ServerState {
    StateIdle,
    StateConnected,
    StateError,
    StateRetrying,
    NumStates
};

std::unordered_map<ServerState, std::string> stateName = {
    {StateIdle, "idle"},
    {StateConnected, "connected"},
    {StateError, "error"},
    {StateRetrying, "retrying"}
};

std::string toString(ServerState state) {
    return stateName[state];
}

ServerState transition(ServerState s) {
    switch (s) {
        case StateIdle:
            return StateConnected;
        case StateConnected:
        case StateRetrying:
            // Suppose we check some predicates here to determine the next state…
            return StateIdle;
        case StateError:
            return StateError;
        default:
            throw std::runtime_error("unknown state: " + std::to_string(s));
    }
}

int main() {
    ServerState ns = transition(StateIdle);
    std::cout << toString(ns) << std::endl;

    ServerState ns2 = transition(ns);
    std::cout << toString(ns2) << std::endl;

    return 0;
}

In C++, enum values are implicitly converted to int, but C++ offers stronger type-checking compared to some other languages. You have to explicitly cast int to ServerState if needed.

To run the program, compile the C++ code and then execute the binary:

$ g++ -o enums enums.cpp
$ ./enums
connected
idle

This gives you an overview of how enums can be used effectively in C++. Now that you understand the basics, you can explore more features of the language.

Interfaces in C++

Struct Embedding in C++

Learn X By Example

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Enums in C++