std::unique_copy() algorithm
- od C++20
- od C++17
- do C++17
// (1)
template< class InputIt, class OutputIt >
constexpr OutputIt unique_copy( InputIt first, InputIt last, OutputIt d_first );
// (2)
template< class InputIt, class OutputIt, class BinaryPredicate >
constexpr OutputIt unique_copy( InputIt first, InputIt last,
OutputIt d_first, BinaryPredicate p );
// (3)
template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2 >
ForwardIt2 unique_copy( ExecutionPolicy&& policy, ForwardIt1 first,
ForwardIt1 last, ForwardIt2 d_first );
// (4)
template< class ExecutionPolicy, class ForwardIt1,
class ForwardIt2, class BinaryPredicate >
ForwardIt2 unique_copy( ExecutionPolicy&& policy,
ForwardIt1 first, ForwardIt1 last,
ForwardIt2 d_first, BinaryPredicate p );
// (1)
template< class InputIt, class OutputIt >
OutputIt unique_copy( InputIt first, InputIt last, OutputIt d_first );
// (2)
template< class InputIt, class OutputIt, class BinaryPredicate >
OutputIt unique_copy( InputIt first, InputIt last,
OutputIt d_first, BinaryPredicate p );
// (3)
template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2 >
ForwardIt2 unique_copy( ExecutionPolicy&& policy, ForwardIt1 first,
ForwardIt1 last, ForwardIt2 d_first );
// (4)
template< class ExecutionPolicy, class ForwardIt1,
class ForwardIt2, class BinaryPredicate >
ForwardIt2 unique_copy( ExecutionPolicy&& policy,
ForwardIt1 first, ForwardIt1 last,
ForwardIt2 d_first, BinaryPredicate p );
// (1)
template< class InputIt, class OutputIt >
OutputIt unique_copy( InputIt first, InputIt last, OutputIt d_first );
// (2)
template< class InputIt, class OutputIt, class BinaryPredicate >
OutputIt unique_copy( InputIt first, InputIt last,
OutputIt d_first, BinaryPredicate p );
Copies the elements from the range [first
; last
), to another range beginning at d_first
in such a way that there are no consecutive equal elements.
Only the first element of each group of equal elements is copied.
-
(1) Elements are compared using
operator==
. -
(2) Elements are compared using the given binary predicate
p
. -
(3 - 4) Same as (1 - 2), but executed according to
policy
.Overload ResolutionThese overloads participate in overload resolution only if
std::is_execution_policy_v<std::decay_t<ExecutionPolicy>>
(do C++20)std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>>
(od C++20) istrue
.
The behavior is undefined
if it is not an equivalence relation.Parameters
first last | The range of elements to process. |
d_first | The beginning of the destination range. |
policy | The execution policy to use. See execution policy for details. |
p | Binary predicate which returns The signature of the function should be equivalent to the following:
|
Type requirements
InputIt | LegacyInputIterator |
OutputIt | LegacyOutputIterator |
ForwardIt1 ForwardIt2 | LegacyForwardIterator |
The type of dereferenced InputIt
must meet the requirements of CopyConstructible, if:
- neither
InputIt
, norOutputIt
satisfies LegacyForwardIterator, or InputIt
doesn't satisfy LegacyForwardIterator and the value type ofInputIt
differs from that ofOutputIt
Return value
Output iterator to the element past the last written element.
Complexity
For nonempty ranges, exactly std::distance(first, last) - 1
applications of the corresponding 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 otherExecutionPolicy
, the behavior is implementation-defined. - If the algorithm fails to allocate memory,
std::bad_alloc
is thrown.
Notes
If InputIt
satisfies LegacyForwardIterator, this function rereads the input in order to detect duplicates.
Otherwise, if OutputIt
satisfies LegacyForwardIterator, and the value type of InputIt
is the same as that of OutputIt
, this function compare *d_first
to *first
.
Otherwise, this function compares *first
to a local element copy.
For the overloads with an ExecutionPolicy
, there may be a performance cost if the value type of ForwardIt1
is not both CopyConstructible and CopyAssignable.
Examples
The following copy-prints a vector, replacing all values over 5
with 99
on the fly.
#include <algorithm>
#include <iostream>
#include <iterator>
#include <string>
int main()
{
std::string s1 {"The string with many spaces!"};
std::cout << "before: " << s1 << '\n';
std::string s2;
std::unique_copy(s1.begin(), s1.end(), std::back_inserter(s2),
[](char c1, char c2) { return c1 == ' ' && c2 == ' '; });
std::cout << "after: " << s2 << '\n';
}
before: The string with many spaces!
after: The string with many spaces!
Hover to see the original license.