std::span::operator[](3)

✨ NAME ✨

Okay bestie, this is the page for std::span::operator[] — title and section number and all: std::span::operator[](3) — from the C++ Standard Libary. Yes, “Libary” is literally how the manual name is spelled on this page, and I am not fixing it. 💅

std::span::operator[] - std::span::operator[]

🌸 SYNOPSIS 🌸

constexpr reference operator[]( size_type idx ) const;  (since C++20)

Returns a reference to the idx-th element of the sequence. Cute and simple. 🫶

🚨 UB ALERT: the behavior is undefined if idx is out of range (i.e., if it is greater than or equal to size()). Not a vibe, no cap, do not do this. 😭

🎀 PARAMETERS 🎀

• idx — the index of the element to access

💖 RETURN VALUE 💖

A reference to the idx-th element of the sequence, i.e., data()[idx]. That’s the whole gift. 🎁

😭 EXCEPTIONS 😭

Throws nothing. Literally nothing. No exception drama here. Periodt.

🧚 EXAMPLE 🧚

// Run this code 👇

#include <cstddef>
#include <iostream>
#include <span>
#include <utility>

void reverse(std::span<int> span)
{
    for (std::size_t i = 0, j = std::size(span); i < j; ++i)
    {
        --j;
        std::swap(span[i], span[j]);
    }
}

void print(std::span<const int> const span)
{
    for (int element : span)
        std::cout << element << ' ';
    std::cout << '\n';
}

int main()
{
    int data[]{1, 2, 3, 4, 5};
    print(data);
    reverse(data);
    print(data);
}

🖥️ OUTPUT

1 2 3 4 5
5 4 3 2 1

👀 SEE ALSO 👀

• at — access specified element with bounds checking (public member function) (C++26)
• data — direct access to the underlying contiguous storage (public member function)
• size — returns the number of elements (public member function)
• as_bytes — converts a span into a view of its underlying bytes
• as_writable_bytes — (function template) (C++20)

Source/version/date sign-off, because the footer is iconic too: this page is from http://cppreference.com, version 2024.06.10, and it’s std::span::operator[](3). Bye bestie — go access some elements, but keep idx in range 👑✨💖