Introduction
Array literals are a convenient way to initialize arrays in many programming languages, including C++. However, by default, C++ does not provide support for custom array literals. In this blog post, we will explore how to implement custom array literals in C++ using user-defined literals.
What are Array Literals?
In C++, an array literal allows you to initialize an array with a list of values enclosed in curly braces {}. For example:
int numbers[] = {1, 2, 3, 4, 5};
However, this syntax can only be used when initializing an array variable. It cannot be used as a standalone expression or as a function argument.
Implementing Custom Array Literals using User-defined Literals
User-defined literals (UDLs) allow us to extend the existing syntax and create custom representations of literals in C++. By defining a UDL, we can introduce our own syntax for initializing arrays.
To create a custom array literal, we need to define a UDL operator function. This function should take a string literal as input and return the desired array. The UDL operator function must be declared with the operator"" prefix, followed by any name we choose. For example:
int operator""_arr(const char* str, size_t size) {
// Process the string and create the desired array
}
Inside the operator function, we have access to the string literal and its size. We can parse the string and create the array using our custom logic.
Let’s illustrate this with an example. Suppose we want to create a custom array literal for initializing arrays with Fibonacci numbers. We can define the operator""_fib function as follows:
#include <array>
std::array<int, size> operator""_fib(size_t size) {
std::array<int, size> arr;
arr[0] = 0;
arr[1] = 1;
for (size_t i = 2; i < size; ++i) {
arr[i] = arr[i - 1] + arr[i - 2];
}
return arr;
}
Now we can use our custom array literal to initialize arrays with Fibonacci numbers:
auto fibArr = 10_fib; // Generates an array containing the first 10 Fibonacci numbers
Conclusion
By using user-defined literals, we can extend the syntax of C++ to create custom array literals. This allows for more convenient and expressive ways to initialize arrays with user-defined values. While it requires some extra effort to implement, custom array literals can greatly enhance the readability and maintainability of C++ code.
#References
#Tags C++ Programming, Arrays, User-defined Literals