[c++] variadic templates

11 Dec 2023

In C++, variadic templates allow you to write functions and classes that can accept any number of arguments of any type. This feature was introduced in C++11 and has significantly enhanced the flexibility and power of template metaprogramming.

What are Variadic Templates?

Variadic templates are templates that can accept a variable number of template parameters. They allow you to define functions or classes that operate on a varying number of arguments.

Syntax

The syntax for defining a variadic template involves using an ellipsis (...) after the template parameter pack, followed by the pack name. For example:

template<typename... Args>
void myFunction(Args... args) {
  // Function body
}

In this example, Args is a template parameter pack, and Args... allows myFunction to accept a variable number of arguments of any type.

Example

Here’s a simple example of using variadic templates to create a function that prints its arguments:

#include <iostream>

void printArgs() {
  std::cout << std::endl;
}

template<typename T, typename... Args>
void printArgs(T firstArg, Args... args) {
  std::cout << firstArg << " ";
  printArgs(args...);
}

int main() {
  printArgs(1, "hello", 3.14, 'c');
  return 0;
}

In this example, the printArgs function uses variadic templates to accept a variable number of arguments, regardless of their types.

Benefits

Variadic templates offer several benefits, such as:

Flexibility: They allow you to write more generic and flexible code that can operate on multiple arguments of different types.
Reduced Code Duplication: They eliminate the need for writing multiple overloaded functions or classes to handle different numbers of arguments.

Using variadic templates can lead to cleaner, more concise code and enable powerful metaprogramming techniques.

Conclusion

Variadic templates in C++ have opened up new possibilities for writing flexible and generic code that can handle a variable number of arguments. By leveraging variadic templates, you can enhance the versatility and expressiveness of your C++ code.

For more detailed information, refer to the C++ reference.