In C++, struct literals allow us to initialize struct objects in a concise and readable manner. However, by default, C++ doesn’t provide support for customizing struct literals. In this blog post, we will explore a technique to create custom struct literals in C++.

Struct Literals in C++

Before diving into customizing struct literals, let’s quickly review how struct literals work in C++. In C++, a struct is a user-defined type that can hold multiple data members. To initialize a struct object, you can use the following syntax:

struct MyStruct {
    int x;
    double y;
};

MyStruct obj = {10, 3.14};

In the above example, we are initializing an object of MyStruct with the values 10 and 3.14.

Customizing Struct Literals

To customize the initialization syntax for structs, we can leverage user-defined literals. User-defined literals allow us to define custom suffixes for literals of specific types. By defining a user-defined literal for our struct, we can modify the syntax used to initialize it.

Let’s see how we can do this for our MyStruct example:

#include <iostream>

struct MyStruct {
    int x;
    double y;
};

MyStruct operator "" _ms(long long x) {
    return {static_cast<int>(x), 0.0};
}

int main() {
    MyStruct obj = 10_ms;
    std::cout << obj.x << ", " << obj.y << std::endl;
    return 0;
}

In the above code, we have defined a user-defined literal operator operator "" _ms that takes a long long parameter. This operator converts the provided value into a MyStruct object by initializing the x member with the provided value and setting y to 0.0.

With this operator defined, we can now initialize MyStruct objects using the _ms suffix, as shown in the main function.

Benefits of Custom Struct Literals

Custom struct literals offer several benefits:

1. Improved Readability: By customizing the syntax, we can make struct initialization more intuitive and expressive, enhancing the readability of the code.

2. Consistency: Custom struct literals allow us to enforce a consistent initialization syntax across different struct types.

3. Abstraction: We can encapsulate complex initialization logic within the user-defined literal operator, providing a more abstract and reusable way to create struct objects.

Conclusion

Custom struct literals offer a powerful way to customize the syntax of struct initialization in C++. By leveraging user-defined literals, we can enhance readability, enforce consistency, and abstract away complex initialization logic. Understanding and using this mechanism can help make our C++ code cleaner and more maintainable.

References:

• C++ User-Defined Literals