std::ranges::range

The range concept defines the requirements of a type that allows iteration over its elements by providing an iterator and sentinel that denote the elements of the range.

Semantic requirements

Given an expression E such that decltype((E)) is T, T models range

• [ ranges::begin(E) ,  ranges::end(E) ) denotes a range
• both ranges::begin(E) and ranges::end(E) are amortized constant time and do not alter the value of E in a manner observable to equality-preserving
• if the type of ranges::begin(E) models forward_iterator, ranges::begin(E) is equality-preserving

Notes

A typical range class only needs to provide two functions:

1. A member function begin() whose return type models input_or_output_iterator.
2. A member function end() whose return type models sentinel_for <It>, where It is the return type of begin()

Alternatively, they can be non-member functions, to be found by argument-dependent lookup.

Example

#include <ranges>
 
// A minimum range
struct SimpleRange
{
    int* begin();
    int* end();
};
static_assert(std::ranges::range<SimpleRange>);
 
// Not a range: no begin/end
struct NotRange
{
    int t {};
};
static_assert(!std::ranges::range<NotRange>);
 
// Not a range: begin does not return an input_or_output_iterator
struct NotRange2
{
    void* begin();
    int* end();
};
static_assert(!std::ranges::range<NotRange2>);
 
int main() {}

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.