Stdto Underlying Function In C++

In this guide, we are going to explore the std::to_underlying function in C++ along with its syntax, parameters, benefits, drawbacks, and a sample illustration.

What is the std::to_underlying function in C++?

The std::to_underlying function serves as a utility function designed to extract the underlying integral value from an enumeration type, a feature introduced in C++17 (header ). This function offers a safer and easier approach to converting enums into integers, facilitating the connection between enum classes and their underlying integral counterparts.

Syntax:

The syntax of std::to_underlying is as follows:

template <typename EnumType>
constexpr std::underlying_type_t<EnumType> to_underlying(EnumType enumerator) noexcept;

Parameters:

• ✅ EnumType: The type of enumeration that has to have its underlying value acquired.
• ✅ Enumerator: An enumeration-type instance that has to have an underlying value.

Return Type:

The return type of std::to_underlying is the integral type corresponding to the underlying enumeration.

For instance, when the enumeration type is declared using either enum class or enum struct, the resulting type will correspond to the integral type specified in the enumeration definition.

How does it operate?

• ✅ An enumerator of the enum type EnumType is passed as an argument to std::to_underlying.
• ✅ It uses implicit conversion to internally convert this enumerator to its underlying integral type.
• ✅ The std::underlying_type type trait is used to find the underlying type.
• ✅ The function returns the enumerator's fundamental integral value.

Advantages:

Several advantages of the std::to_underlying function in C++ .

• ✅ Type safety: It guarantees a clear and well-defined conversion from enum to integral type.
• ✅ Clarity: When the goal to convert enums to integers is made clear, the code becomes more expressive.
• ✅ Compile-time Determination: Since the conversion is constexpr, it can be assessed at compile-time.
• ✅ Prevents Mistakes: It assists in avoiding unintentional conversions or comparisons between different enum types.

Disadvantages:

Several benefits of utilizing the std::to_underlying function in C++.

• ✅ For C++20 and Beyond: The std::to_underlying function is specifically designed for usage in C++20 and later versions. It is crucial to note that any codebase aiming at older standards will not have access to this feature.
• ✅ Strictly for Integral Underlying Types: This function is tailored for enumerations that possess integral underlying types. Enumerations with class or floating-point underlying types are not compatible with std::to_underlying.

Usage:

• ✅ The std::to_underlying function is generally employed in situations when we must carry out operations using an enumerator's underlying integral value.
• ✅ The integral form of an enumerator might be required for assignments, comparisons, or any other kind of operation.

Example:

Let's consider a scenario to demonstrate the std::to_underlying function within C++.

#include <iostream>
#include <type_traits> // For std::to_underlying

// Define an enumeration with an underlying type
enum class Color : uint8_t {
    Red = 1,
    Green = 2,
    Blue = 3
};

int main() {
    // Create an instance of the enumeration
    Color color = Color::Green;

    // Use std::to_underlying to get the underlying value of the enum
    auto underlying_value = std::to_underlying(color);

    // Print the underlying value
    std::cout << "The underlying value of Color::Green is: " << static_cast<int>(underlying_value) << std::endl;

    return 0;
}

Output:

The underlying value of Color::Green is: 2

Explanation:

The following implementation demonstrates the ability we can use the std::to_underlying functioning, and this has been introduced in C++20, for obtaining the fundamental value associated with an enumeration.

• ✅ Header Inclusion and Enumeration Definitions: In order to call std::tounderlying, our application first incorporates the header. Therefore, it generates an instance of Color that utilizes the underlying type uint8t. By applying the enum class syntax, the source code constructs a completely typed enumeration the fact that avoids implicit conversions, strengthening type safety and readability. The fundamental type uint8_t ensures that enum members remain unchanged as 8-bit unsigned integers and decimals therefore might help minimize memory.
• ✅ Creating an Enumeration Instance: In the main function, an instance of the Color enumeration is created and assigned the value Color::Green. This demonstrates how to work with enumerations by initializing them with predefined values. The choice of Color::Green is arbitrary but shows how to interact with enum values.
• ✅ Extracting the Underlying Value: The core of the example is the use of std::tounderlying. This function is applied to the color instance, extracting its underlying integer value. The call to std::tounderlying(color) returns the value 2, which corresponds to Color::Green. This function provides a straightforward and type-safe way to obtain the integral representation of the enum value, avoiding manual casts and potential errors.
• ✅ Outputting the Result: Finally, the program prints the underlying value using std::cout. The staticcast<int> is used to ensure the value is displayed as an integer. This cast converts the uint8t value to a more familiar integer type for display purposes. The output of the program confirms that Color::Green has an underlying value of 2, demonstrating that the std::to_underlying function correctly retrieves the integral value from the enumeration.

Complexity:

The former std::tounderlying function in C++ has been designed as a utility feature in C++20 that provides a simple method for accessing the basic integral form of an enumeration. This method is a part of the <typetraits> header and proves to be beneficial when working with enumerations that have a defined underlying type other than the default int.

Enumeration structures in C++ can specify a specific underlying type, as demonstrated by enum class Color: unsigned char {Red, Green, Blue };. By default, an enumeration's underlying type is int, but assigning a different type can enhance memory usage efficiency and compatibility with APIs requiring specific integral types. The std::to_underlying method allows developers to access the underlying type in a secure and type-safe way.

The level of overhead associated with std::tounderlying has now become negligible. The approach is commonly carried out by simply casting the enumeration to its underlying type. For instance, if we consider an enumeration like Color: unsigned char { Red, Green, Blue };, employing std::tounderlying(Color::Red) would convert the Color::Red enumerator to unsigned char. This method is generally efficient and operates in constant time, O(1), as it solely involves type conversions without complex calculations.

Conclusion:

In summary, the addition of the std::to_underlying function in C++20 represents a significant improvement in handling enumerations within modern programming languages such as C++. This feature enables developers to produce more explicit and descriptive code by providing a secure and uncomplicated approach to accessing the underlying integer value of a specific enumeration. This particular function caters to a growing demand among programmers to access the raw numeric representation of enum values without resorting to risky casts or intricate type conversions.

The direct approach of std::to_underlying enhances its effectiveness, as it performs its intended task efficiently with minimal additional processing time, typically operating at a consistent speed. This streamlined performance is achieved by directly converting to the underlying type, guaranteeing swift and reliable execution throughout the process.

Additionally, the std::tounderlying function highlights the progressing development of C++ towards promoting safer and more user-friendly programming methodologies. With the integration of this feature into the standard library, C++20 equips programmers with resources that improve the transparency and sustainability of code. Consequently, std::tounderlying streamlines the manipulation of enumerations and strengthens the adherence to optimal type handling techniques in the language.