std::experimental::ranges::prev

 

C++

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Concepts library (C++20)

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Technical Specifications

 

Technical specifications

Filesystem library (filesystem TS)

Library fundamentals (library fundamentals TS)

Library fundamentals 2 (library fundamentals 2 TS)

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Ranges

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Ranges

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Iterators library

Iterator concepts
Readable Writable WeaklyIncrementable Incrementable	Iterator Sentinel SizedSentinel	InputIterator ForwardIterator BidirectionalIterator RandomAccessIterator	OutputIterator
Indirect callable concepts
IndirectUnaryInvocableIndirectRegularUnaryInvocable	IndirectUnaryPredicate	IndirectRelation	IndirectStrictWeakOrder
Common algorithm requirements
IndirectlyMovable IndirectlyMovableStorable	IndirectlyCopyable IndirectlyCopyableStorable	IndirectlySwappable IndirectlyComparable	Permutable Mergeable Sortable
Concept utilities
indirect_result_of	projected
Iterator utilities and operations
iter_move iter_swap	advance distance	next prev
Iterator traits
difference_type value_type reference_trvalue_reference_titer_common_reference_t iterator_category	input_iterator_tagoutput_iterator_tagforward_iterator_tagbidirectional_iterator_tagrandom_access_iterator_tag	ranges::iterator_traits std::iterator_traits<InputIterator>std::iterator_traits<OutputIterator>
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reverse_iterator move_iterator move_sentinel	back_insert_iterator front_insert_iterator insert_iterator	common_iterator counted_iterator default_sentinel	danglingsafe_iterator_t unreachable
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istream_iterator	ostream_iterator	istreambuf_iterator	ostreambuf_iterator

 

Defined in header <experimental/ranges/iterator>
namespace {     constexpr /* unspecified */ prev = /* unspecified */; }		(ranges TS) (customization point object)
Call signature
template< Iterator I > constexpr I prev(I i);	(1)
template< Iterator I > constexpr I prev(I i, ranges::difference_type_t<I> n);	(2)
template< Iterator I > constexpr I prev(I i, ranges::difference_type_t<I> n, I bound);	(3)

Decrements the iterator i n times, or until bound is reached, whichever comes first, and returns the decremented iterator.

1) Equivalent to --i; return i;.

2) Equivalent to ranges::advance(i, -n); return i;.

3) Equivalent to ranges::advance(i, -n, bound); return i;.

Customization point objects

The name ranges::prev denotes a customization point object, which is a function object of a literal Semiregular class type (denoted, for exposition purposes, as PrevT). All instances of PrevT are equal. Thus, ranges::prev can be copied freely and its copies can be used interchangeably.

Given a set of types Args..., if std::declval<Args>()... meet the requirements for arguments to ranges::prev above, PrevT will satisfy ranges::Invocable<const PrevT, Args...>. Otherwise, no function call operator of PrevT participates in overload resolution.

In every translation unit in which ranges::prev is defined, it refers to the same instance of the customization point object. (This means that it can be used freely in things like inline functions and function templates without violating the one-definition rule.)

Return value

The decremented iterator.

See also

prev (C++11)	decrement an iterator (function template)
advance	advances an iterator by given distance (function template)
next	increment an iterator (function template)
distance	returns the distance between an iterator and a sentinel, or between the beginning and the end of a range (function template)