# replace_copy

Category: algorithms | Component type: function

### Prototype

    template <class InputIterator, class OutputIterator, class T>
    OutputIterator replace_copy(InputIterator first, InputIterator last,
                                OutputIterator result, const T& old_value,
                                const T& new_value);

### Description

`Replace_copy` copies elements from the range `[first, last)` to the range `[result, result + (last-first))`, except that any element equal to `old_value` is not copied; `new_value` is copied instead. More precisely, for every integer `n` such that `0 <= n < last-first`, `replace_copy` performs the assignment `*(result+n) = new_value` if `*(first+n) == old_value`, and `*(result+n) = *(first+n)` otherwise.

### Definition

Defined in the standard header algorithm, and in the nonstandard backward-compatibility header algo.h.

### Requirements on types

- `InputIterator` is a model of Input Iterator.
- `OutputIterator` is a model of Output Iterator.
- `T` is EqualityComparable, and may be compared for equality with objects of `InputIterator`'s value type.
- `T` is Assignable.
- `T` is convertible to a type in `OutputIterator`'s set of value types.

### Preconditions

- `[first, last)` is a valid range.
- There is enough space in the output range to store the copied values. That is, `[result, result + (last-first))` is a valid range.
- `result` is not an iterator within the range `[first, last)`.

### Complexity

Linear. `Replace_copy` performs exactly `last - first` comparisons for equality and exactly `last - first` assignments.

### Example

    vector<int> V1;
    V1.push_back(1);
    V1.push_back(2);
    V1.push_back(3);
    V1.push_back(1);

    vector<int> V2(4);

    replace_copy(V1.begin(), V1.end(), V2.begin(), 1, 99);
    assert(V[0] == 99 && V[1] == 2 && V[2] == 3 && V[3] == 99);

### Notes

### See also

`copy`, `replace`, `replace_if`, `replace_copy_if`

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