Template Function thrust::copy_if(InputIterator, InputIterator, OutputIterator, Predicate)¶
Function Documentation¶
-
template<typename
InputIterator
, typenameOutputIterator
, typenamePredicate
>
OutputIteratorthrust
::
copy_if
(InputIterator first, InputIterator last, OutputIterator result, Predicate pred) This version of
copy_if
copies elements from the range[first,last)
to a range beginning atresult
, except that any element which causespred
tofalse
is not copied.copy_if
is stable, meaning that the relative order of elements that are copied is unchanged.More precisely, for every integer
n
such that0 <= n < last-first
,copy_if
performs the assignment*result = *(first+n)
andresult
is advanced one position ifpred(*(first+n))
. Otherwise, no assignment occurs andresult
is not advanced.The following code snippet demonstrates how to use
copy_if
to perform stream compaction to copy even numbers to an output range.- Return
result + n
, wheren
is equal to the number of timespred
evaluated totrue
in the range[first, last)
.- Pre
The ranges
[first, last)
and[result, result + (last - first))
shall not overlap.- Parameters
first
: The beginning of the sequence from which to copy.last
: The end of the sequence from which to copy.result
: The beginning of the sequence into which to copy.pred
: The predicate to test on every value of the range[first, last)
.
- Template Parameters
InputIterator
: is a model of Input Iterator, andInputIterator's
value_type
is convertible toPredicate's
argument_type
.OutputIterator
: is a model of Output Iterator.Predicate
: is a model of Predicate.
#include <thrust/copy.h> ... struct is_even { __host__ __device__ bool operator()(const int x) { return (x % 2) == 0; } }; ... const int N = 6; int V[N] = {-2, 0, -1, 0, 1, 2}; int result[4]; thrust::copy_if(V, V + N, result, is_even()); // V remains {-2, 0, -1, 0, 1, 2} // result is now {-2, 0, 0, 2}
- See
remove_copy_if