How do you do bounds checking with std span?

Question

std::vector and pretty much all other containers have a very convenient way of bounds checking: at(). std::span doesn't have that apparently.

• Why?
• Is there a replacement? Other than rolling out your own at()?

Answer 1

Pretty clunky but something like this:

1. using position

template<class Container>
auto& at(Container&& c, std::size_t pos){
    if(pos >= c.size())
        throw std::out_of_range("out of bounds");
    return c[pos];
}

2. using iterators:

template<class Iterator, class Container>
auto& at(Container&& c, Iterator&& it){
    if(std::distance(c.begin(), it) >= c.size())
        throw std::out_of_range("out of bounds");
    return *it;
}