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Difference between revisions of "cpp/algorithm/remove copy"

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< cpp‎ | algorithm
m (seealso par)
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{{dcl begin}}
 
{{dcl begin}}
 
{{dcl header | algorithm}}
 
{{dcl header | algorithm}}
−
{{dcl | num=1 |
+
{{dcl | since= | num= 1 |1=
 
template< class InputIt, class OutputIt, class T >
 
template< class InputIt, class OutputIt, class T >
 
OutputIt remove_copy( InputIt first, InputIt last, OutputIt d_first,
 
OutputIt remove_copy( InputIt first, InputIt last, OutputIt d_first,
 
                       const T& value );
 
                       const T& value );
 
}}
 
}}
−
{{dcl | num=2 |
+
{{dcl | since=c++17 | num= 2 |1=
 +
template< class ExecutionPolicy, class InputIt, class OutputIt, class T >
 +
OutputIt remove_copy( ExecutionPolicy&& policy, InputIt first, InputIt last, OutputIt d_first,
 +
                      const T& value );}}
 +
{{dcl | since= | num= 3 |1=
 
template< class InputIt, class OutputIt, class UnaryPredicate >
 
template< class InputIt, class OutputIt, class UnaryPredicate >
 
OutputIt remove_copy_if( InputIt first, InputIt last, OutputIt d_first,
 
OutputIt remove_copy_if( InputIt first, InputIt last, OutputIt d_first,
 
                         UnaryPredicate p );
 
                         UnaryPredicate p );
 
}}
 
}}
 +
{{dcl | since=c++17 | num= 4 |1=
 +
template< class ExecutionPolicy, class InputIt, class OutputIt, class UnaryPredicate >
 +
OutputIt remove_copy_if( ExecutionPolicy&& policy, InputIt first, InputIt last, OutputIt d_first,
 +
                        UnaryPredicate p );}}
 
{{dcl end}}
 
{{dcl end}}
  
−
Copies elements from the range {{tt|[first, last)}}, to another range beginning at {{tt|d_first}}, omitting the elements which satisfy specific criteria. The first version ignores the elements that are equal to {{tt|value}}, the second version ignores the elements for which predicate {{tt|p}} returns {{c|true}}. Source and destination ranges cannot overlap.
+
Copies elements from the range {{tt|[first, last)}}, to another range beginning at {{tt|d_first}}, omitting the elements which satisfy specific criteria. Source and destination ranges cannot overlap.
 +
 
 +
@1@ Ignores all elements that are equal to {{tt|value}}.
 +
@3@ Ignores all elements for which predicate {{tt|p}} returns {{c|true}}.
 +
@2,4@ Same as {{v|1,3}}, but executed according to {{tt|policy}}. These overloads do not participate in overload resolution unless {{c|std::is_execution_policy_v<std::decay_t<ExecutionPolicy>>}} is true
  
 
===Parameters===
 
===Parameters===
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{{par | d_first | the beginning of the destination range. }}
 
{{par | d_first | the beginning of the destination range. }}
 
{{par | value | the value of the elements not to copy}}
 
{{par | value | the value of the elements not to copy}}
 +
{{par exec pol}}
 
{{par hreq}}
 
{{par hreq}}
 
{{par req concept | InputIt | InputIterator}}
 
{{par req concept | InputIt | InputIterator}}
Line 33: Line 46:
 
===Complexity===
 
===Complexity===
 
Exactly {{tt|last - first}} applications of the predicate.
 
Exactly {{tt|last - first}} applications of the predicate.
 +
 +
===Exceptions===
 +
{{cpp/algorithm/parallel_exceptions_reporting_behavior|singular=no}}
  
 
===Possible implementation===
 
===Possible implementation===

Revision as of 09:58, 21 March 2016

 
C++
 
Algorithm library
Constrained algorithms and algorithms on ranges (C++20)
Constrained algorithms, e.g. ranges::copy, ranges::sort, ...
Execution policies (C++17)
Non-modifying sequence operations
Batch operations
(C++17)
Search operations
(C++11)                (C++11)(C++11)

Modifying sequence operations
Copy operations
(C++11)
(C++11)
(C++11)
Swap operations
Transformation operations
Generation operations
Removing operations
remove_copyremove_copy_if
Order-changing operations
(until C++17)(C++11)
(C++20)(C++20)
Sampling operations
(C++17)

Sorting and related operations
Partitioning operations
Sorting operations
Binary search operations
(on partitioned ranges)
Set operations (on sorted ranges)
Merge operations (on sorted ranges)
Heap operations
Minimum/maximum operations
(C++11)
(C++17)
Lexicographical comparison operations
(C++20)
Permutation operations
C library
Numeric operations
Operations on uninitialized memory
 
Defined in header <algorithm>
template< class InputIt, class OutputIt, class T >

OutputIt remove_copy( InputIt first, InputIt last, OutputIt d_first,

                      const T& value );
 (1)
template< class ExecutionPolicy, class InputIt, class OutputIt, class T >

OutputIt remove_copy( ExecutionPolicy&& policy, InputIt first, InputIt last, OutputIt d_first,

                      const T& value );
 (2) (since C++17)
template< class InputIt, class OutputIt, class UnaryPredicate >

OutputIt remove_copy_if( InputIt first, InputIt last, OutputIt d_first,

                         UnaryPredicate p );
 (3)
template< class ExecutionPolicy, class InputIt, class OutputIt, class UnaryPredicate >

OutputIt remove_copy_if( ExecutionPolicy&& policy, InputIt first, InputIt last, OutputIt 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. These overloads do not participate in overload resolution unless std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> is true

Contents

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

Template:par req concept Template:par req concept Template:par req concept

Return value

Iterator to the element past the last element copied.

Complexity

Exactly last - first applications of the predicate.

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

 removes elements satisfying specific criteria
(function template) [edit]
(C++11)
 copies a range of elements to a new location
(function template) [edit]
(parallelism TS)
 parallelized version of std::remove_copy
(function template) [edit]
(parallelism TS)
 parallelized version of std::remove_copy_if
(function template) [edit]
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