# 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 InputIterator.
• `OutputIterator` is a model of OutputIterator.
• `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

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