5 advanced features of C++17 and how to use them

  • Post author:
  • Post category:C++
  • Post comments:0 Comments

C++ is a powerful programming language that has undergone many changes and improvements over the years. C++17, the latest version of the language, introduces a number of advanced features that can make your code more efficient, readable, and maintainable. In this blog post, we’ll take a look at five of the most exciting features of C++17 and how to use them in your code.

1. Structured bindings

Structured bindings are a new feature in C++17 that allow you to bind multiple variables to the members of a struct or class. This can make your code more readable and maintainable, as it allows you to access the members of a struct or class directly, rather than having to use pointers or references.

Here’s an example of how to use structured bindings:

struct Point {
    int x;
    int y;
};

Point p {1, 2};

auto [x, y] = p;
std::cout << x << ", " << y << std::endl; // Output: 1, 2

In this example, the variables x and y are directly bound to the members of the Point struct, allowing us to access them directly. This can be especially useful when working with large, complex structs or classes, as it can make your code more readable and easier to maintain.

2. Fold expressions

Fold expressions are a new feature in C++17 that allow you to perform fold operations on a parameter pack. A fold operation is a way to combine the elements of a parameter pack into a single value, using a binary operator.

Here’s an example of how to use fold expressions:

template<typename... Args>
auto sum(Args... args) {
    return (... + args);
}

std::cout << sum(1, 2, 3, 4, 5) << std::endl; // Output: 15

In this example, the fold expression (… + args) is used to add up all of the elements in the parameter pack args. This can be a very powerful tool when working with variadic templates, as it allows you to perform complex operations on a variable number of arguments.

3. if constexpr

if constexpr is a new feature in C++17 that allows you to conditionally compile code based on the type of a variable or expression. This can be a powerful tool when working with templates, as it allows you to write code that is optimized for different types.

Here’s an example of how to use if constexpr:

template<typename T>
void print(T value) {
    if constexpr (std::is_same<T, int>::value) {
        std::cout << value << std::endl;
    } else if constexpr (std::is_same<T, double>::value) {
        std::cout << std::fixed << value << std::endl;
    } else {
        static_assert(false, "Unsupported type");
    }
}

In this example, the if constexpr statement is used to conditionally compile the code based on the type of the value parameter. If value is of type int, it will be printed as is, if value is double, it will be printed with fixed precision and any other type will trigger a static_assert. This allows for the code to be optimized for different types, making it more efficient and easier to maintain.

std::variant

std::variant is a new feature in C++17 that allows you to store a value of one of several different types in a single variable. This can be useful when working with code that needs to handle multiple types of data, as it allows you to use a single variable to store values of different types, rather than having to use separate variables for each type.

Here’s an example of how to use std::variant:

std::variant<int, double, std::string> value;
value = 10;
std::cout << std::get<int>(value) << std::endl; // Output: 10
value = 3.14;
std::cout << std::get<double>(value) << std::endl; // Output: 3.14
value = "hello";
std::cout << std::get<std::string>(value) << std::endl; // Output: hello

In this example, the std::variant variable value can be used to store a value of type int, double, or std::string. The std::get function is used to retrieve the value stored in the variant and the type of the value can be checked using std::variant::index() or std::holds_alternative()

5. std::optional

std::optional is a new feature in C++17 that allows you to store a value of a certain type, or no value at all. This can be useful when working with code that needs to handle the possibility of missing data, as it allows you to use a single variable to represent both a value and the absence of a value.

Here’s an example of how to use std::optional:

std::optional<int> value;
value = 10;
std::cout << *value << std::endl; // Output: 10
value.reset();
std::cout << value.has_value() << std::endl; // Output: false

In this example, the std::optional variable value can be used to store a value of type int, or no value at all. The value can be set using the operator = or by using std::make_optional() and can be checked for its availability using the has_value() function.

These are just a few examples of the advanced features of C++17. C++17 also includes other features such as nested namespaces, string_view, and more. These features can make your code more efficient, readable, and maintainable. As always, it is important to use these features in a way that makes sense for your specific use case, and to keep in mind the principles of good coding practices.

Leave a Reply