std::replace_copy_if

template <class InputIterator, class OutputIterator, class UnaryPredicate, class T>  OutputIterator replace_copy_if (InputIterator first, InputIterator last,                                  OutputIterator result, UnaryPredicate pred,                                  const T& new_value);

Copy range replacing value

Copies the elements in the range [first,last) to the range beginning at result, replacing those for which pred returns true by new_value.

The behavior of this function template is equivalent to:

template <class InputIterator, class OutputIterator, class UnaryPredicate, class T>
  OutputIterator replace_copy_if (InputIterator first, InputIterator last,
                                  OutputIterator result, UnaryPredicate pred,
                                  const T& new_value)
{
  while (first!=last) {
    *result = (pred(*first))? new_value: *first;
    ++first; ++result;
  }
  return result;
}

Parameters

first, last: Input iterators to the initial and final positions in a sequence. The range copied is [first,last), which contains all the elements between first and last, including the element pointed by first but not the element pointed by last.
result: Output iterator to the initial position of the range where the resulting sequence is stored. The range includes as many elements as [first,last).
The pointed type shall support being assigned a value of type T.
pred: Unary function that accepts an element in the range as argument, and returns a value convertible to bool. The value returned indicates whether the element is to be replaced in the copy (if true, it is replaced).
The function shall not modify its argument.
This can either be a function pointer or a function object.
new_value: Value to assign to replaced values.

The ranges shall not overlap.

Return value

An iterator pointing to the element that follows the last element written in the result sequence.

Example

// replace_copy_if example
#include <iostream>     // std::cout
#include <algorithm>    // std::replace_copy_if
#include <vector>       // std::vector

bool IsOdd (int i) { return ((i%2)==1); }

int main () {
  std::vector<int> foo,bar;

  // set some values:
  for (int i=1; i<10; i++) foo.push_back(i);          // 1 2 3 4 5 6 7 8 9

  bar.resize(foo.size());   // allocate space
  std::replace_copy_if (foo.begin(), foo.end(), bar.begin(), IsOdd, 0);
                                                        // 0 2 0 4 0 6 0 8 0

  std::cout << "bar contains:";
  for (std::vector<int>::iterator it=bar.begin(); it!=bar.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  return 0;
}

Output:

second contains: 0 2 0 4 0 6 0 8 0

Complexity

Linear in the distance between first and last: Applies pred and performs an assignment for each element.

Data races

The objects in the range [first,last) are accessed.
The objects in the range between result and the returned value are modified.

Exceptions

Throws if any of pred, the element assignments or the operations on iterators throws.
Note that invalid arguments cause undefined behavior.