std::span front() method

since C++20

constexpr reference front() const;

Returns a reference

to the first element in the container.

Undefined Behavior

Calling front() on an empty span is undefined behavior

.

Parameters

(none)

Return value

A reference to the first element.

Complexity

Constant - O(1).

Exceptions

(none)

Notes

For a span s, the expression s.front() is equivalent to *s.begin() and s[0].

Example

Main.cpp

#include <span>
#include <iostream>
 
void print(std::span<const int> const data)
{
    for (auto offset{0U}; offset != data.size(); ++offset) {
        std::cout << data.subspan(offset).front() << ' ';
    }
    std::cout << '\n';
}
 
int main()
{
    constexpr int data[] { 0, 1, 2, 3, 4, 5, 6 };
    print({data, 4});
}

Output

0 1 2 3