Getting the comfort of std::string without the cost of constructing std::string objects

The std::string class is a really useful class because it simplifies dealing with strings so much. A flaw is that if we want to pass around a substring of it, we need to pass a pointer and a length variable, two iterators, or a copy of the substring. We did that in the previous recipe, where we removed the surrounding whitespace from a string by taking a copy of the substring range that does not contain the surrounding whitespace.

If we want to pass a string or a substring to a library that does not even support std::string, we can only provide a raw string pointer, which is a bit disappointing, because it sets us back to the old C days. Just as with the substring problem, a raw pointer does not carry information about the string length with it. This way, one would have to implement a bundle of a pointer and a string length.

In a simplified way, this is exactly what std::string_view is. It is available...