std::counted_iterator<I>::operator++,+,+=,--,-,-=

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Technical specifications

Symbols index

External libraries

 

Iterator library

Iterator concepts
indirectly_readable (C++20) indirectly_writable (C++20) weakly_incrementable (C++20) incrementable (C++20) input_or_output_iterator (C++20) sentinel_for (C++20) sized_sentinel_for (C++20)	input_iterator (C++20) output_iterator (C++20) forward_iterator (C++20) bidirectional_iterator (C++20) random_access_iterator (C++20) contiguous_iterator (C++20)
Iterator primitives
iterator_traits input_iterator_tagoutput_iterator_tagforward_iterator_tagbidirectional_iterator_tagrandom_access_iterator_tagcontiguous_iterator_tag (C++20) iterator (deprecated in C++17)	incrementable_traits (C++20) indirectly_readable_traits (C++20) iter_value_titer_difference_titer_reference_titer_const_reference_titer_rvalue_reference_titer_common_reference_t (C++20)(C++20)(C++20)(C++23)(C++20)(C++20)
Algorithm concepts and utilities
Indirect callable concepts
indirectly_unary_invocableindirectly_regular_unary_invocable (C++20)(C++20)   indirect_unary_predicate (C++20)	indirect_binary_predicate (C++20) indirect_equivalence_relation (C++20) indirect_strict_weak_order (C++20)
Common algorithm requirements
indirectly_movable (C++20) indirectly_movable_storable (C++20) indirectly_copyable (C++20) indirectly_copyable_storable (C++20)	indirectly_swappable (C++20) indirectly_comparable (C++20) permutable (C++20) mergeable (C++20) sortable (C++20)
Utilities
indirect_result_t (C++20)	projected (C++20)
Iterator adaptors
reverse_iterator move_iterator (C++11) move_sentinel (C++20) common_iterator (C++20) counted_iterator (C++20) basic_const_iterator (C++23) const_iterator (C++23) const_sentinel (C++23) back_insert_iterator front_insert_iterator insert_iterator	make_reverse_iterator (C++14) make_move_iterator (C++11) default_sentinel_tdefault_sentinel (C++20)(C++20) unreachable_sentinel_tunreachable_sentinel (C++20)(C++20) make_const_iterator (C++23) make_const_sentinel (C++23) back_inserter front_inserter inserter
Stream iterators
istream_iterator ostream_iterator	istreambuf_iterator ostreambuf_iterator
Iterator customization points
ranges::iter_move (C++20)
ranges::iter_swap (C++20)
Iterator operations
advance distance prev (C++11) next (C++11)	ranges::advance (C++20) ranges::distance (C++20) ranges::prev (C++20) ranges::next (C++20)
Range access
begincbegin (C++11)(C++14) endcend (C++11)(C++14) sizessize (C++17)(C++20)	rbegincrbegin (C++14)(C++14) rendcrend (C++14)(C++14) empty (C++17) data (C++17)

 

std::counted_iterator

Member functions

counted_iterator::counted_iterator (C++20)

counted_iterator::operator= (C++20)

counted_iterator::base (C++20)

counted_iterator::count (C++20)

counted_iterator::operator*counted_iterator::operator-> (C++20)(C++20)

counted_iterator::operator[] (C++20)

counted_iterator::operator++counted_iterator::operator++(int)counted_iterator::operator+counted_iterator::operator+=counted_iterator::operator--counted_iterator::operator--(int)counted_iterator::operator-counted_iterator::operator-= (C++20)(C++20)(C++20)(C++20)(C++20)(C++20)(C++20)(C++20)

Non-member functions

operator==operator<=> (C++20)(C++20)

operator==(default_sentinel_t) (C++20)

operator+ (C++20)

operator- (C++20)

operator-(default_sentinel_t) (C++20)

iter_move (C++20)

iter_swap (C++20)

Helper classes

iterator_traits (C++20)

 

constexpr counted_iterator& operator++();	(1)	(since C++20)
constexpr decltype(auto) operator++( int );	(2)	(since C++20)
constexpr counted_iterator operator++( int )   requires std::forward_iterator<I>;	(3)	(since C++20)
constexpr counted_iterator& operator--()   requires std::bidirectional_iterator<I>;	(4)	(since C++20)
constexpr counted_iterator operator--( int )   requires std::bidirectional_iterator<I>;	(5)	(since C++20)
constexpr counted_iterator operator+( std::iter_difference_t<I> n ) const   requires std::random_access_iterator<I>;	(6)	(since C++20)
constexpr counted_iterator& operator+=( std::iter_difference_t<I> n )   requires std::random_access_iterator<I>;	(7)	(since C++20)
constexpr counted_iterator operator-( std::iter_difference_t<I> n ) const   requires std::random_access_iterator<I>;	(8)	(since C++20)
constexpr counted_iterator& operator-=( std::iter_difference_t<I> n )   requires std::random_access_iterator<I>;	(9)	(since C++20)

Increments or decrements the underlying iterator current and the distance to the end length.

The behavior of these functions is undefined if the length would be set to a minus value.

1) Pre-increments by one. Equivalent to ++current; --length; return *this;.

2) Post-increments by one. Equivalent to --length; try { return current++; } catch(...) { ++length; throw; }.

3) Post-increments by one. Equivalent to counted_iterator temp{*this}; ++*this; return temp;.

4) Pre-decrements by one. Equivalent to --current; ++length; return *this;.

5) Post-decrements by one. Equivalent to counted_iterator temp{*this}; --*this; return temp;.

6) Returns an iterator adaptor which is advanced by n. Equivalent to return counted_iterator(current + n, length - n);.

7) Advances the iterator adaptor by n. Equivalent to current += n; length -= n; return *this;.

8) Returns an iterator adaptor which is advanced by -n. Equivalent to return counted_iterator(current - n, length + n);.

9) Advances the iterator adaptor by -n. Equivalent to current -= n; length += n; return *this;.

Parameters

n

-

the number of positions to increment or decrement the iterator adaptor

Return value

1) *this.

2-3) A copy of *this that was made before the change.

4) *this.

5) A copy of *this that was made before the change.

6) An iterator adaptor which is advanced by n.

7) *this.

8) An iterator adaptor which is advanced by -n.

9) *this.

Example

Run this code

#include <cassert>
#include <initializer_list>
#include <iterator>
 
int main()
{
    const auto v = {1, 2, 3, 4, 5, 6};
    std::counted_iterator<std::initializer_list<int>::iterator> it1 {v.begin(), 5};
 
    ++it1;              assert(*it1 == 2 && it1.count() == 4);  // (1)
    auto it2 = it1++;   assert(*it2 == 2 && *it1 == 3);         // (3)
    --it1;              assert(*it1 == 2 && it1.count() == 4);  // (4)
    auto it3 = it1--;   assert(*it3 == 2 && *it1 == 1);         // (5)
    auto it4 = it1 + 3; assert(*it4 == 4 && it4.count() == 2);  // (6)
    auto it5 = it4 - 3; assert(*it5 == 1 && it5.count() == 5);  // (8)
    it1 += 3;           assert(*it1 == 4 && it1.count() == 2);  // (7)
    it1 -= 3;           assert(*it1 == 1 && it1.count() == 5);  // (9)
}

See also

operator+ (C++20)	advances the iterator (function template)
operator- (C++20)	computes the distance between two iterator adaptors (function template)