C++ std::array::crbegin

The std::array::crbegin function returns a constant reverse iterator pointing to the last element of the array. This iterator allows read-only access to the array elements in reverse order. It is commonly used when you need to traverse a const array or enforce non-modifiable access while iterating in reverse.

Syntax of std::array::crbegin

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const_reverse_iterator crbegin() const noexcept;

Parameters

The std::array::crbegin function does not take any parameters.

Return Value

Returns a constant reverse iterator pointing to the last element of the array, which is the first element in reverse order. If the array is empty, the returned iterator is equal to std::array::crend.

Examples for std::array::crbegin

Example 1: Iterating Through an Array in Reverse Using std::array::crbegin

This example demonstrates iterating through the elements of a std::array in reverse order using crbegin() and crend():

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#include <iostream>
#include <array>

int main() {
    std::array<int, 5> arr = {10, 20, 30, 40, 50};

    std::cout << "Array elements in reverse order: ";
    for (auto it = arr.crbegin(); it != arr.crend(); ++it) {
        std::cout << *it << " ";
    }
    std::cout << std::endl;

    return 0;
}

Explanation:

Define an array: A std::array of size 5 is initialized with elements {10, 20, 30, 40, 50}.
Use crbegin() and crend(): The crbegin() function provides a constant reverse iterator pointing to the last element, while crend() points to one before the first element of the array in reverse order.
Iterate in reverse: A for loop is used to traverse the array in reverse order. The elements are accessed using the dereference operator *it, and the constant reverse iterator ensures the array elements remain unmodified.

Output:

Array elements in reverse order: 50 40 30 20 10

Example 2: Using std::array::crbegin with a Standard Algorithm

This example demonstrates using std::array::crbegin with the std::for_each algorithm to print the elements of a std::array in reverse order:

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#include <iostream>
#include <array>
#include <algorithm>

int main() {
    std::array<int, 5> arr = {1, 2, 3, 4, 5};

    std::cout << "Array elements in reverse order: ";
    std::for_each(arr.crbegin(), arr.crend(), [](int x) {
        std::cout << x << " ";
    });
    std::cout << std::endl;

    return 0;
}

Explanation:

Original array: The array arr is initialized with elements {1, 2, 3, 4, 5}.
Use std::for_each: The std::for_each algorithm is applied to the range defined by crbegin() and crend(). A lambda function is used to print each element.
Traverse in reverse: The crbegin() iterator starts at the last element, and the iteration ends before the first element as indicated by crend().
Output the result: The lambda function ensures each element is printed in reverse order.

Output:

Array elements in reverse order: 5 4 3 2 1

Exception Handling in std::array::crbegin

The std::array::crbegin function does not throw exceptions as it is marked noexcept. This ensures safe access to a constant reverse iterator pointing to the last element of the array.

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C++ std::array::crbegin