Constrained algorithms and algorithms on ranges(C++20) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Constrained algorithms, e.g.ranges::copy,ranges::sort, ... | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Execution policies(C++17) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Numeric operations | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Operations on uninitialized memory | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Defined in header <algorithm> | ||
(1) | ||
template<class InputIt,class OutputIt,class T> OutputIt remove_copy( InputIt first, InputIt last, | (constexpr since C++20) (until C++26) | |
template<class InputIt,class OutputIt, class T=typenamestd::iterator_traits | (since C++26) | |
(2) | ||
template<class ExecutionPolicy, class ForwardIt1,class ForwardIt2,class T> | (since C++17) (until C++26) | |
template<class ExecutionPolicy, class ForwardIt1,class ForwardIt2, | (since C++26) | |
template<class InputIt,class OutputIt,class UnaryPred> OutputIt remove_copy_if( InputIt first, InputIt last, | (3) | (constexpr since C++20) |
template<class ExecutionPolicy, class ForwardIt1,class ForwardIt2,class UnaryPred> | (4) | (since C++17) |
Copies elements from the range[
first,
last)
, to another range beginning atd_first, omitting the elements which satisfy specific criteria.
std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> istrue. | (until C++20) |
std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>> istrue. | (since C++20) |
If*d_first=*first is invalid(until C++20)*first is notwritable tod_first(since C++20), the program is ill-formed.
If source and destination ranges overlap, the behavior is undefined.
Contents |
first, last | - | the pair of iterators defining the sourcerange of elements to copy |
d_first | - | the beginning of the destination range |
value | - | the value of the elements not to copy |
policy | - | theexecution policy to use |
Type requirements | ||
-InputIt must meet the requirements ofLegacyInputIterator. | ||
-OutputIt must meet the requirements ofLegacyOutputIterator. | ||
-ForwardIt1, ForwardIt2 must meet the requirements ofLegacyForwardIterator. | ||
-UnaryPred must meet the requirements ofPredicate. |
Iterator to the element past the last element copied.
Given\(\scriptsize N\)N asstd::distance(first, last):
For the overloads with an ExecutionPolicy, there may be a performance cost ifForwardIt1
'svalue_type
is notMoveConstructible.
The overloads with a template parameter namedExecutionPolicy
report errors as follows:
ExecutionPolicy
is one of thestandard policies,std::terminate is called. For any otherExecutionPolicy
, the behavior is implementation-defined.remove_copy (1) |
---|
template<class InputIt,class OutputIt,class T=typenamestd::iterator_traits<InputIt>::value_type>constexpr 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 (3) |
template<class InputIt,class OutputIt,class UnaryPred>constexpr OutputIt remove_copy_if(InputIt first, InputIt last, OutputIt d_first, UnaryPred p){for(; first!= last;++first)if(!p(*first))*d_first++=*first;return d_first;} |
Feature-test macro | Value | Std | Feature |
---|---|---|---|
__cpp_lib_algorithm_default_value_type | 202403 | (C++26) | List-initialization for algorithms(1,2) |
#include <algorithm>#include <complex>#include <iomanip>#include <iostream>#include <iterator>#include <string>#include <vector> int main(){// Erase the hash characters '#' on the fly.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"; // Erase {1, 3} value on the fly.std::vector<std::complex<double>> nums{{2,2},{1,3},{4,8},{1,3}}; std::remove_copy(nums.begin(), nums.end(),std::ostream_iterator<std::complex<double>>(std::cout),#ifdef __cpp_lib_algorithm_default_value_type{1,3});// T gets deduced#elsestd::complex<double>{1,3});#endif}
Output:
before: "#Return #Value #Optimization"after: "Return Value Optimization"(2,2)(4,8)
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 beEqualityComparable, butthe value type of ForwardIt is not alwaysT | required*d_first=*first to be valid instead |
removes elements satisfying specific criteria (function template)[edit] | |
(C++11) | copies a range of elements to a new location (function template)[edit] |
(C++11) | copies a range dividing the elements into two groups (function template)[edit] |
(C++20)(C++20) | copies a range of elements omitting those that satisfy specific criteria (algorithm function object)[edit] |