std::span<T,Extent>::front - cppreference.com

From cppreference.com

`constexpr reference front() const;`		(since C++20)

Returns a reference to the first element in the span.

If empty() is true, the behavior is undefined.

(until C++26)

If empty() is true:

If the implementation is hardened, a contract violation occurs. Moreover, if the contract-violation handler returns under “observe” evaluation semantic, the behavior is undefined.
If the implementation is not hardened, the behavior is undefined.

(since C++26)

Return value

A reference to the first element.

Complexity

Constant.

Notes

For a span c, the expression c.front() is equivalent to *c.begin().

Example

#include <iostream>
#include <span>

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:

Return value

Complexity

Notes

Example

See also