std::remove_copy, std::remove_copy_if

 

C++

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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)

Execution support 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>
	(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. Source and destination ranges cannot overlap.

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. This overload participates in overload resolution only if std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> is true

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.

Return value

Iterator to the element past the last element copied.

Complexity

Exactly last - first applications of the predicate.

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

First version
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; }
Second version
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 spaces on the fly.

Run this code

#include <algorithm>
#include <iterator>
#include <string>
#include <iostream>
int main()
{
    std::string str = "Text with some   spaces";
    std::cout << "before: " << str << "\n";
 
    std::cout << "after:  ";
    std::remove_copy(str.begin(), str.end(),
                     std::ostream_iterator<char>(std::cout), ' ');
    std::cout << '\n';
}

Output:

before: Text with some   spaces
after:  Textwithsomespaces

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)