std::move_backward

 

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)

Diagnostics library

Memory management library

Metaprogramming library(C++11)

General utilities library

Containers library

Iterators library

Ranges library(C++20)

Algorithms library

Strings library

Text processing library

Numerics library

Date and time library

Input/output library

Filesystem library(C++17)

Concurrency support library(C++11)

Execution control library(C++26)

Technical specifications

Symbols index

External libraries

 

Algorithm library

Constrained algorithms and algorithms on ranges(C++20)
Constrained algorithms, e.g. ranges::copy, ranges::sort, ...
Execution policies (C++17)
is_execution_policy (C++17)   execution::seqexecution::parexecution::par_unseqexecution::unseq (C++17)    (C++17)(C++17)(C++20)	execution::sequenced_policyexecution::parallel_policyexecution::parallel_unsequenced_policyexecution::parallel_unsequenced (C++17)(C++17)(C++17)(C++20)
Non-modifying sequence operations Batch operations for_each for_each_n (C++17) Search operations all_ofany_ofnone_of (C++11)                (C++11)(C++11) countcount_if mismatch equal findfind_iffind_if_not (C++11) find_end find_first_of adjacent_find search search_n Modifying sequence operations Copy operations copycopy_if (C++11) copy_backward copy_n (C++11) move (C++11) move_backward (C++11) Swap operations swap iter_swap swap_ranges Transformation operations replacereplace_if transform replace_copyreplace_copy_if Generation operations fill fill_n generate generate_n Removing operations removeremove_if unique remove_copyremove_copy_if unique_copy Order-changing operations reverse reverse_copy rotate rotate_copy random_shuffleshuffle (until C++17)(C++11) shift_leftshift_right (C++20)(C++20) Sampling operations sample (C++17)	Sorting and related operations Partitioning operations partition partition_copy (C++11)   stable_partition is_partitioned (C++11) partition_point (C++11) Sorting operations sort stable_sort partial_sort partial_sort_copy is_sorted (C++11) is_sorted_until (C++11) nth_element Binary search operations (on partitioned ranges) lower_bound upper_bound equal_range binary_search Set operations (on sorted ranges) includes set_union set_intersection set_difference set_symmetric_difference Merge operations (on sorted ranges) merge inplace_merge Heap operations push_heap pop_heap make_heap sort_heap is_heap (C++11) is_heap_until (C++11) Minimum/maximum operations max min minmax (C++11) clamp (C++17) max_element min_element minmax_element (C++11) Lexicographical comparison operations lexicographical_compare lexicographical_compare_three_way (C++20) Permutation operations next_permutation prev_permutation is_permutation (C++11) C library qsort bsearch
Numeric operations
iota (C++11) inner_product adjacent_difference    accumulate reduce (C++17) transform_reduce (C++17)	partial_sum inclusive_scan (C++17)    exclusive_scan (C++17) transform_inclusive_scan (C++17) transform_exclusive_scan (C++17)
Operations on uninitialized memory
uninitialized_copy uninitialized_move (C++17)    uninitialized_fill uninitialized_copy_n (C++11) uninitialized_move_n (C++17) uninitialized_fill_n	destroy (C++17) destroy_n (C++17) destroy_at (C++17) construct_at (C++20)       uninitialized_default_construct (C++17) uninitialized_value_construct (C++17) uninitialized_default_construct_n (C++17) uninitialized_value_construct_n (C++17)

 

Defined in header <algorithm>
template<class BidirIt1, class BidirIt2 > BidirIt2 move_backward( BidirIt1 first, BidirIt1 last, BidirIt2 d_last );		(since C++11) (constexpr since C++20)

Moves the elements from the range [first, last), to another range ending at d_last. The elements are moved in reverse order (the last element is moved first), but their relative order is preserved.

If d_last is within (first, last], the behavior is undefined. In this case, std::move may be used instead.

Parameters

first, last	-	the pair of iterators defining the source range of elements to move
d_last	-	end of the destination range
Type requirements
- BidirIt1, BidirIt2 must meet the requirements of LegacyBidirectionalIterator.

Return value

Iterator in the destination range, pointing at the last element moved.

Complexity

Exactly std::distance(first, last) move assignments.

Possible implementation

template<class BidirIt1, class BidirIt2> BidirIt2 move_backward(BidirIt1 first, BidirIt1 last, BidirIt2 d_last){while(first != last)*(--d_last)= std::move(*(--last));   return d_last;}

Notes

When moving overlapping ranges, std::move is appropriate when moving to the left (beginning of the destination range is outside the source range) while std::move_backward is appropriate when moving to the right (end of the destination range is outside the source range).

Example

Run this code

#include <algorithm>#include <iostream>#include <iterator>#include <string>#include <string_view>#include <vector>   using container =std::vector<std::string>;   void print(std::string_view comment, const container& src, const container& dst ={}){auto prn =[](std::string_view name, const container& cont){std::cout<< name;for(constauto&s : cont)std::cout<<(s.empty()?"∙": s.data())<<' ';std::cout<<'\n';};std::cout<< comment <<'\n'; prn("src: ", src);if(dst.empty())return; prn("dst: ", dst);}   int main(){ container src{"foo", "bar", "baz"}; container dst{"qux", "quux", "quuz", "corge"}; print("Non-overlapping case; before move_backward:", src, dst); std::move_backward(src.begin(), src.end(), dst.end()); print("After:", src, dst);   src ={"snap", "crackle", "pop", "lock", "drop"}; print("Overlapping case; before move_backward:", src); std::move_backward(src.begin(), std::next(src.begin(), 3), src.end()); print("After:", src);}

Output:

Non-overlapping case; before move_backward: src: foo bar baz dst: qux quux quuz corge After: src: ∙ ∙ ∙ dst: qux foo bar baz Overlapping case; before move_backward: src: snap crackle pop lock drop After: src: ∙ ∙ snap crackle pop

See also

move (C++11)	moves a range of elements to a new location (function template)
ranges::move_backward (C++20)	moves a range of elements to a new location in backwards order (algorithm function object)