replaced_if

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##### replaced_if

Syntax | Code
--- | ---
Pipe | `rng | boost::adaptors::replaced_if(pred, new_value)`
Function | `boost::adaptors::replace_if(rng, pred, new_value)`

- Precondition:
  - The range `value_type` is convertible to the argument type of `pred`.
  - `new_value` is convertible to the `value_type` of the range.
- Postconditions: For all elements `x` in the returned range, the value `x` is equal to the value of `pred(y) ? new_value : y` where `y` is the corresponding element in the original range.
- Range Category: Single Pass Range
- Range Return Type: `boost::replaced_if_range<decltype(rng)>`
- Returned Range Category: The range category of `rng`.

###### replaced_if example

    #include <boost/range/adaptor/replaced_if.hpp>
    #include <boost/range/algorithm/copy.hpp>
    #include <boost/assign.hpp>
    #include <iterator>
    #include <iostream>
    #include <vector>

    struct is_even
    {
        bool operator()(int x) const { return x % 2 == 0; }
    };

    int main(int argc, const char* argv[])
    {
        using namespace boost::adaptors;
        using namespace boost::assign;

        std::vector<int> input;
        input += 1,2,3,4,5,6,7,8,9;

        boost::copy(
            input | replaced_if(is_even(), 10),
            std::ostream_iterator<int>(std::cout, ","));

        return 0;
    }

This would produce the output:

    1,10,3,10,5,10,7,10,9,