thrust

◆ unique_copy() [2/4]

template<typename InputIterator , typename OutputIterator >
OutputIterator thrust::unique_copy ( InputIterator  first,
InputIterator  last,
OutputIterator  result 
)

unique_copy copies elements from the range [first, last) to a range beginning with result, except that in a consecutive group of duplicate elements only the first one is copied. The return value is the end of the range to which the elements are copied.

The reason there are two different versions of unique_copy is that there are two different definitions of what it means for a consecutive group of elements to be duplicates. In the first version, the test is simple equality: the elements in a range [f, l) are duplicates if, for every iterator i in the range, either i == f or else *i == *(i-1). In the second, the test is an arbitrary BinaryPredicate binary_pred: the elements in [f, l) are duplicates if, for every iterator i in the range, either i == f or else binary_pred(*i, *(i-1)) is true.

This version of unique_copy uses operator== to test for equality.

Parameters
firstThe beginning of the input range.
lastThe end of the input range.
resultThe beginning of the output range.
Returns
The end of the unique range [result, result_end).
Template Parameters
InputIteratoris a model of Input Iterator, and InputIterator's value_type is a model of Equality Comparable.
OutputIteratoris a model of Output Iterator and and InputIterator's value_type is convertible to OutputIterator's value_type.
Precondition
The range [first,last) and the range [result, result + (last - first)) shall not overlap.

The following code snippet demonstrates how to use unique_copy to compact a sequence of numbers to remove consecutive duplicates.

#include <thrust/unique.h>
...
const int N = 7;
int A[N] = {1, 3, 3, 3, 2, 2, 1};
int B[N];
int *result_end = thrust::unique_copy(A, A + N, B);
// The first four values of B are now {1, 3, 2, 1} and (result_end - B) is 4
// Values beyond result_end are unspecified
See also
unique
http://www.sgi.com/tech/stl/unique_copy.html