Views Over Contiguous Data

arene::base::span provides a view over a contiguous sequence of objects. It takes 2 template parameters; the first is the type of the elements, and the second is the extent of the sequence, either arene::base::dynamic_extent or the number of elements in the sequence. If the extent is omitted, then it defaults to arene::base::dynamic_extent. If the extent is the number of elements, then any objects of that span type always refer to a sequence with that number of elements. If the extent is arene::base::dynamic_extent, then the number of elements is a dynamic property, and may vary between instances of the span type.

Thus arene::base::span<int, 5> is a fixed-size span of 5 elements of type int, whereas arene::base::span<int> is shorthand for arene::base::span<int, arene::base::dynamic_extent>, which is a dynamic-sized span that covers any number of elements of type int.

The number of elements in a given arene::base::span object is always passed to the constructor, either explicitly, or implicitly (such as via the bounds of an array, or the size of a container). For fixed-size spans, this is checked, and it is a precondition violation if it does not match the fixed size. The number of elements referenced by a span can be obtained with the size member function. For a fixed-size span, this always returns the fixed size. For a dynamic-sized span, this returns the actual number of elements referenced by this particular span object.

Elements of the sequence referenced by a span can be accessed by the indexing operator (arene::base::span::operator[]). Attempting to access an element beyond the end of the span is a precondition violation.

Note: The indexing operator returns a reference to the element type of the span, independent of the const-ness of the span itself: indexing into const arene::base::span<int> returns an int&, while indexing into arene::base::span<const int> returns a const int&.

arene::base::span is also a valid range, with iterators, for use with range-based for and standard library algorithms.

arene::base::span is a backport of std::span