Template Function thrust::replace_if(ForwardIterator, ForwardIterator, InputIterator, Predicate, const T&)¶

Function Documentation¶

template<typename ForwardIterator, typename InputIterator, typename Predicate, typename T> void thrust::replace_if(ForwardIterator first, ForwardIterator last, InputIterator stencil, Predicate pred, const T &new_value)

replace_if replaces every element in the range [first, last) for which pred(*s) returns true with new_value. That is: for every iterator i in the range [first, last), and s in the range [stencil, stencil + (last - first)), if pred(*s) is true then it performs the assignment *i = new_value.

The following code snippet demonstrates how to use

replace_if to replace a device_vector's element with 0 when its corresponding stencil element is less than zero.

Parameters

first: The beginning of the sequence of interest.
last: The end of the sequence of interest.
stencil: The beginning of the stencil sequence.
pred: The predicate to test on every value of the range [first,last).
new_value: The new value to replace elements which pred(*i) evaluates to true.

Template Parameters

ForwardIterator: is a model of Forward Iterator, and ForwardIterator is mutable.
InputIterator: is a model of Input Iterator, and InputIterator's value_type is convertible to Predicate's argument_type.
Predicate: is a model of Predicate.
T: is a model of Assignable, and T is convertible to ForwardIterator's value_type.

#include <thrust/replace.h>
#include <thrust/device_vector.h>

struct is_less_than_zero
{
  __host__ __device__
  bool operator()(int x)
  {
    return x < 0;
  }
};

...

thrust::device_vector<int> A(4);
A[0] =  10;
A[1] =  20;
A[2] =  30;
A[3] =  40;

thrust::device_vector<int> S(4);
S[0] = -1;
S[1] =  0;
S[2] = -1;
S[3] =  0;

is_less_than_zero pred;
thrust::replace_if(A.begin(), A.end(), S.begin(), pred, 0);

// A contains [0, 20, 0, 40]

See: http://www.sgi.com/tech/stl/replace_if.html
See: replace
See: replace_copy
See: replace_copy_if