thrust::placeholders Namespace Reference

Facilities for constructing simple functions inline. More...

Variables
static const thrust::detail::functional::placeholder< 0 >::type	_1
static const thrust::detail::functional::placeholder< 1 >::type	_2
static const thrust::detail::functional::placeholder< 2 >::type	_3
static const thrust::detail::functional::placeholder< 3 >::type	_4
static const thrust::detail::functional::placeholder< 4 >::type	_5
static const thrust::detail::functional::placeholder< 5 >::type	_6
static const thrust::detail::functional::placeholder< 6 >::type	_7
static const thrust::detail::functional::placeholder< 7 >::type	_8
static const thrust::detail::functional::placeholder< 8 >::type	_9
static const thrust::detail::functional::placeholder< 9 >::type	_10

Detailed Description

Facilities for constructing simple functions inline.

Objects in the thrust::placeholders namespace may be used to create simple arithmetic functions inline in an algorithm invocation. Combining placeholders such as _1 and _2 with arithmetic operations such as + creates an unnamed function object which applies the operation to their arguments.

The type of placeholder objects is implementation-defined.

The following code snippet demonstrates how to use the placeholders _1 and _2 with thrust::transform to implement the SAXPY computation:

#include <thrust/device_vector.h>
#include <thrust/transform.h>
#include <thrust/functional.h>

int main()
{
  thrust::device_vector<float> x(4), y(4);
  x[0] = 1;
  x[1] = 2;
  x[2] = 3;
  x[3] = 4;

  y[0] = 1;
  y[1] = 1;
  y[2] = 1;
  y[3] = 1;

  float a = 2.0f;

  using namespace thrust::placeholders;

  thrust::transform(x.begin(), x.end(), y.begin(), y.begin(),
    a * _1 + _2
  );

  // y is now {3, 5, 7, 9}
}