Tuples vs Variadic Templates

Tuples and variadic templates are both ways to work with a variable number of values, but they have different use cases.

Use tuples when:

• You need to store and pass around a fixed number of related values.
• The values have different types and don't share a common base class.
• You want to return multiple values from a function.
• You need to work with the values individually using std::get, std::tuple_element, etc.

For example, a function that returns a player's name and score is a good candidate for a tuple:

1std::tuple<std::string, int> getInfo(int id);

On the other hand, use variadic templates when:

• You're writing a function template that needs to accept an arbitrary number of arguments.
• The arguments have the same type, or share a common base class.
• You want to perform an operation on all the arguments in a uniform way.

For instance, a function that computes the sum of an arbitrary number of integers is a good fit for variadic templates:

1template <typename... Args>
2int sum(Args... args) {
3  return (... + args);
4}

In this case, the sum function accepts any number of arguments (captured by Args...) and adds them together using a fold expression.

Sometimes, you can use the two techniques together. For example, you might have a variadic function template that forwards its arguments to another function as a tuple:

1template <typename... Args>
2void log(Args&&... args) {
3  std::tuple<Args...> data(
4    std::forward<Args>(args)...);
5  writeToLog(data);
6}

Here, log accepts any number of arguments, perfect forwards them to construct a tuple, and then passes that tuple to writeToLog.

In summary, use tuples for bundling related values, and variadic templates for writing functions that operate on an arbitrary number of arguments in a uniform way. The two techniques can also be combined when needed.