Range Concept Reference

Definition

CGAL and the STL heavily use the concepts of iterators and iterator ranges to describe linear sequences of elements, and algorithms operating on these.

The Range concept aims at encapsulating an iterator range, by providing access to the first and past-the-end iterators of a range. The advantage is that the syntax for passing ranges is much more concise than passing two arguments separately.

Ranges come in different categories depending on the category of their iterator : mutable or constant (modifiability of the elements pointed to), and forward, bidirectional or random-access. The category can be queried using std::iterator_traits and the corresponding iterator type. Note that the concepts Range and ConstRange do not require anything on the category or the value type of the iterator. It must be precised in the documentation of any model of these concepts. For example, in the case of a vector of points, one would say: This type is a model of Range concept, its iterator type is random-access and its value type is Point.

Boost also offers the Boost.Range library which provides good support for ranges.

Finally, let us note that ranges, in general (especially in template context) need to be passed and returned by (const) reference for efficiency. This is a difference with iterators which are typically passed by value.

Refines:

ConstRange

Boost's Range concept

Has Models:

STL containers

Types
typedef unspecified_type	const_iterator
	The constant iterator type.
typedef unspecified_type	iterator
	The iterator type. More...
typedef unspecified_type	size_type
	An unsigned integral type that can represent the size of a range.

Member functions
const_iterator	begin () const
	returns the const iterator pointing to the first element.
const_iterator	end () const
	returns the past-the-end const iterator.
iterator	begin ()
	returns the iterator pointing to the first element.
iterator	end ()
	returns the past-the-end iterator.
size_type	size () const
	returns the size of the range.
bool	empty () const
	returns whether the range is empty.

Member Typedef Documentation

iterator

typedef unspecified_type Range::iterator

The iterator type.

It must be convertible to const_iterator.