When writing code, it is common to come across situations where you need a function that can accept different types of arguments. This is where templated functions come in handy. In this article, we will learn how to write a templated function that can accept either a std::optional or an arithmetic type, and select the correct underlying type.
Understanding Templated Functions
Before diving into the specifics of our function, let's first understand what a templated function is. In simple terms, a templated function is a function that can be used with different types of arguments. It allows you to write a single function definition that can be used for multiple types, eliminating the need to write separate functions for each type.
Templated functions are defined using the template keyword, followed by the template parameter(s) in angle brackets. For example:
template <typename T>
void myFunction(T arg) {
// function body
}
In the above example, T is the template parameter, and it represents a generic type that will be determined when the function is called.
Accepting std::optional or Arithmetic Types
Now, let's move on to our specific case of writing a templated function that can accept either a std::optional or an arithmetic type. We want our function to behave differently depending on the type of argument passed.
To achieve this, we can use type traits and function overloading. Type traits provide a way to introspect and manipulate the properties of types at compile-time. In our case, we will use the std::is_arithmetic trait to determine if the argument is an arithmetic type.
Here's how our function definition would look like:
template <typename T>
void myFunction(T arg) {
if constexpr (std::is_arithmetic<T>::value) {
// do something for arithmetic types
} else if (std::is_same<std::optional<T>, T>::value) {
// do something for std::optional types
} else {
// handle other types
}
}
Let's break down the code:
- The
if constexprstatement is used to conditionally compile code based on the result of a compile-time expression. In our case, we are using it to select the appropriate branch based on the type ofT. - The
std::is_arithmetictrait is used to check if the typeTis an arithmetic type. If it is, we execute the code inside the first branch. - The
std::is_sametrait is used to check if the typeTis the same asstd::optional<T>. If it is, we execute the code inside the second branch. - If none of the above conditions are met, we execute the code inside the
elseblock, which handles other types.
By using this approach, our function can now accept both std::optional and arithmetic types, and perform different operations based on the type of argument passed.
Writing a templated function that can accept different types of arguments is a powerful technique in C++. By using type traits and function overloading, we can create flexible and reusable code that adapts to different types at compile-time. In our specific case, we learned how to write a templated function that accepts either a std::optional or an arithmetic type, and selects the correct underlying type. This allows us to handle different types of arguments in a single function, improving code readability and maintainability.
References
| Source | Link |
|---|---|
| C++ Reference - std::optional | https://en.cppreference.com/w/cpp/utility/optional |
| C++ Reference - std::is_arithmetic | https://en.cppreference.com/w/cpp/types/is_arithmetic |
| C++ Reference - std::is_same | https://en.cppreference.com/w/cpp/types/is_same |