cpp / intermediate
Snippet
Type-Safe Sum Types with Variant
std::variant is a type-safe union introduced in C++17. Unlike traditional C-style unions, it knows which type it currently holds and works with std::visit to provide compile-time safety when accessing the value.
snippet.cpp
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#include <iostream>#include <variant>#include <string>int main() {std::variant<int, std::string> data;data = "Gemini";std::visit([](auto&& arg) {using T = std::decay_t<decltype(arg)>;if constexpr (std::is_same_v<T, int>)std::cout << "Integer: " << arg << std::endl;else if constexpr (std::is_same_v<T, std::string>)std::cout << "String: " << arg << std::endl;}, data);return 0;}
Breakdown
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std::variant<int, std::string> data;
Defines a variable that can safely hold either an integer or a string.
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std::visit([](auto&& arg) { ... }, data);
Applies a lambda function to the active member of the variant in a type-safe way.