std::replace_copy

Defined in header <algorithm>

template< class InputIt, class OutputIt, class T >
OutputIt replace_copy( InputIt first, InputIt last, OutputIt d_first,
                       const T& old_value, const T& new_value );

(1)

template< class InputIt, class OutputIt, class UnaryPredicate, class T >
OutputIt replace_copy_if( InputIt first, InputIt last, OutputIt d_first,
                          UnaryPredicate p, const T& new_value );

(2)

Copies the all elements from the range [first, last) to another range beginning at d_first replacing all elements satisfying specific criteria with new_value. The first version replaces the elements that are equal to old_value, the second version replaces elements for which predicate p returns true. The source and destination ranges cannot overlap.

Parameters

first, last	-	the range of elements to copy
d_first	-	the beginning of the destination range
old_value	-	the value of elements to replace
p	-	unary predicate which returns `true` if the element value should be replaced. The signature of the predicate function should be equivalent to the following: `bool pred(const Type &a);` The signature does not need to have `const &`, but the function must not modify the objects passed to it. The type `Type` must be such that an object of type `InputIt` can be dereferenced and then implicitly converted to `Type`.
new_value	-	the value to use as replacement
Type requirements
- `InputIt` must meet the requirements of `InputIterator`.
- `OutputIt` must meet the requirements of `OutputIterator`.

Return value

Iterator to the element past the last element copied.

Complexity

Exactly last - first applications of the predicate.

Possible implementation

First version

template<class InputIt, class OutputIt, class T>
OutputIt replace_copy(InputIt first, InputIt last, OutputIt d_first,
                      const T& old_value, const T& new_value)
{
    for (; first != last; ++first) {
        *d_first++ = (*first == old_value) ? new_value : *first;
    }
    return d_first;
}

Second version

template<class InputIt, class OutputIt, 
         class UnaryPredicate, class T>
OutputIt replace_copy_if(InputIt first, InputIt last, OutputIt d_first,
                         UnaryPredicate p, const T& new_value)
{
    for (; first != last; ++first) {
        *d_first++ = p( *first ) ? new_value : *first;
    }
    return d_first;
}

Example

The following copy prints a vector, replacing all values over 5 with 99 on the fly.

#include <algorithm>
#include <vector>
#include <iostream>
#include <iterator>
#include <functional>
  
int main()
{
    std::vector<int> v{5, 7, 4, 2, 8, 6, 1, 9, 0, 3};
    std::replace_copy_if(v.begin(), v.end(),
                         std::ostream_iterator<int>(std::cout, " "),
                         [](int n){return n > 5;}, 99);
    std::cout << '\n';
}

Output:

1	`5 99 4 2 99 99 1 99 0 3`

removeremove_if	removes elements satisfying specific criteria (function template)
std::experimental::parallel::replace_copy (parallelism TS)	parallelized version of `std::replace_copy` (function template)
std::experimental::parallel::replace_copy_if (parallelism TS)	parallelized version of `std::replace_copy_if` (function template)

Links:

http://en.cppreference.com/w/cpp/algorithm/replace_copy

doc_CPP

2025-01-10 15:47:30

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