std::remove_copy, std::remove_copy_if

 

C++

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Feature test macros (C++20)

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Ranges library (C++20)

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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
all_ofany_ofnone_of (C++11)(C++11)(C++11) for_each for_each_n (C++17)	countcount_if mismatch equal adjacent_find	search search_n lexicographical_compare lexicographical_compare_three_way (C++20)	findfind_iffind_if_not (C++11) find_end find_first_of
Modifying sequence operations
copycopy_if (C++11) copy_n (C++11) copy_backward move (C++11) move_backward (C++11) shift_leftshift_right (C++20)(C++20) transform	fill fill_n generate generate_n swap iter_swap swap_ranges sample (C++17)	removeremove_if replacereplace_if reverse rotate unique random_shuffle (until C++17)	remove_copyremove_copy_if replace_copyreplace_copy_if reverse_copy rotate_copy unique_copy shuffle (C++11)
Partitioning operations
is_partitioned (C++11) partition_point (C++11)	partition partition_copy (C++11)	stable_partition
Sorting operations
is_sorted (C++11) is_sorted_until (C++11)	sort stable_sort	partial_sort partial_sort_copy	nth_element
Binary search operations
lower_bound	upper_bound	binary_search	equal_range
Set operations (on sorted ranges)
merge inplace_merge	set_difference set_intersection	set_symmetric_difference set_union	includes
Heap operations
is_heap (C++11) is_heap_until (C++11)	make_heap sort_heap	push_heap pop_heap
Minimum/maximum operations
max max_element	min min_element	minmax (C++11) minmax_element (C++11)	clamp (C++17)
Permutations
is_permutation (C++11)	next_permutation	prev_permutation
Numeric operations
iota (C++11) inner_product adjacent_difference	accumulate reduce (C++17) transform_reduce (C++17)	transform_inclusive_scan (C++17) transform_exclusive_scan (C++17)	partial_sum inclusive_scan (C++17) exclusive_scan (C++17)
Operations on uninitialized storage
uninitialized_copy uninitialized_move (C++17) uninitialized_fill	uninitialized_copy_n (C++11) uninitialized_move_n (C++17) uninitialized_fill_n	uninitialized_default_construct (C++17) uninitialized_value_construct (C++17) uninitialized_default_construct_n (C++17) uninitialized_value_construct_n (C++17)	destroy (C++17) destroy_n (C++17) destroy_at (C++17) construct_at (C++20)
C library
qsort	bsearch

 

Defined in header <algorithm>
	(1)
template< class InputIt, class OutputIt, class T > OutputIt remove_copy( InputIt first, InputIt last,                       OutputIt d_first, const T& value );			(until C++20)
template< class InputIt, class OutputIt, class T > constexpr OutputIt remove_copy( InputIt first, InputIt last,                                 OutputIt d_first, const T& value );			(since C++20)
template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2, class T > ForwardIt2 remove_copy( ExecutionPolicy&& policy,                         ForwardIt1 first, ForwardIt1 last,                         ForwardIt2 d_first, const T& value );		(2)	(since C++17)
		(3)
template< class InputIt, class OutputIt, class UnaryPredicate > OutputIt remove_copy_if( InputIt first, InputIt last,                          OutputIt d_first, UnaryPredicate p );				(until C++20)
template< class InputIt, class OutputIt, class UnaryPredicate > constexpr OutputIt remove_copy_if( InputIt first, InputIt last,                                    OutputIt d_first, UnaryPredicate p );				(since C++20)
template< class ExecutionPolicy, class ForwardIt1,           class ForwardIt2, class UnaryPredicate > ForwardIt2 remove_copy_if( ExecutionPolicy&& policy,                            ForwardIt1 first, ForwardIt1 last,                            ForwardIt2 d_first, UnaryPredicate p );			(4)	(since C++17)

Copies elements from the range [first, last), to another range beginning at d_first, omitting the elements which satisfy specific criteria.

1) Ignores all elements that are equal to value.

3) Ignores all elements for which predicate p returns true.

2,4) Same as (1,3), but executed according to policy. These overloads do not participate in overload resolution unless

std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> is true.	(until C++20)
std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>> is true.	(since C++20)

If source and destination ranges overlap, the behavior is undefined.

Parameters

first, last	-	the range of elements to copy
d_first	-	the beginning of the destination range.
value	-	the value of the elements not to copy
policy	-	the execution policy to use. See execution policy for details.
Type requirements
- InputIt must meet the requirements of LegacyInputIterator.
- OutputIt must meet the requirements of LegacyOutputIterator.
- ForwardIt1, ForwardIt2 must meet the requirements of LegacyForwardIterator.
- UnaryPredicate must meet the requirements of Predicate.

The expression *d_first = *first must be valid.	(until C++20)
*first must be writable to d_first.	(since C++20)

Return value

Iterator to the element past the last element copied.

Complexity

Given N as std::distance(first, last):

1,2) exactly N comparisons with value using operator==

3,4) exactly N applications of the predicate p

For the overloads with an ExecutionPolicy, there may be a performance cost if ForwardIt1's value_type is not MoveConstructible.

Exceptions

The overloads with a template parameter named ExecutionPolicy report errors as follows:

• If execution of a function invoked as part of the algorithm throws an exception and ExecutionPolicy is one of the standard policies, std::terminate is called. For any other ExecutionPolicy, the behavior is implementation-defined.
• If the algorithm fails to allocate memory, std::bad_alloc is thrown.

Possible implementation

remove_copy
template<class InputIt, class OutputIt, class T> OutputIt remove_copy(InputIt first, InputIt last, OutputIt d_first, const T& value) { for (; first != last; ++first) if (!(*first == value)) *d_first++ = *first; return d_first; }
remove_copy_if
template<class InputIt, class OutputIt, class UnaryPredicate> OutputIt remove_copy_if(InputIt first, InputIt last, OutputIt d_first, UnaryPredicate p) { for (; first != last; ++first) if (!p(*first)) *d_first++ = *first; return d_first; }

Example

The following code outputs a string while erasing the hash characters '#' on the fly.

Run this code

#include <algorithm>
#include <iterator>
#include <string>
#include <iostream>
#include <iomanip>
 
int main()
{
    std::string str = "#Return #Value #Optimization";
    std::cout << "before: " << std::quoted(str) << "\n";
 
    std::cout << "after:  \"";
    std::remove_copy(str.begin(), str.end(),
                     std::ostream_iterator<char>(std::cout), '#');
    std::cout << "\"\n";
}

Output:

before: "#Return #Value #Optimization"
after:  "Return Value Optimization"

Defect reports

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

DR	Applied to	Behavior as published	Correct behavior
LWG 779	C++98	T was required to be EqualityComparable, but the value type of ForwardIt is not always T	required *d_first= *first to be valid instead

See also

removeremove_if	removes elements satisfying specific criteria (function template)
copycopy_if (C++11)	copies a range of elements to a new location (function template)
partition_copy (C++11)	copies a range dividing the elements into two groups (function template)
ranges::remove_copyranges::remove_copy_if (C++20)(C++20)	copies a range of elements omitting those that satisfy specific criteria (niebloid)