std::replace, std::replace_if

 

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all_of any_of none_of (C++11) (C++11) (C++11) for_each count count_if mismatch equal	find find_if find_if_not (C++11) find_end find_first_of adjacent_find search search_n
Modifying sequence operations
copy copy_if (C++11) copy_n (C++11) copy_backward move (C++11) move_backward (C++11) fill fill_n transform generate generate_n remove remove_if remove_copy remove_copy_if	replace replace_if replace_copy replace_copy_if swap swap_ranges iter_swap reverse reverse_copy rotate rotate_copy random_shuffle shuffle   (C++11) unique unique_copy
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is_partitioned (C++11) partition partition_copy (C++11)	stable_partition partition_point (C++11)
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is_sorted (C++11) is_sorted_until (C++11) sort	partial_sort partial_sort_copy stable_sort nth_element
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lower_bound upper_bound	binary_search equal_range
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iota (C++11) accumulate inner_product	adjacent_difference partial_sum
C library
qsort	bsearch

 

Defined in header <algorithm>
template< class ForwardIterator, class T > void replace( ForwardIterator first, ForwardIterator last,               const T& old_value, const T& new_value );	(1)
template< class ForwardIterator, class UnaryPredicate, class T > void replace_if( ForwardIterator first, ForwardIterator last,                  UnaryPredicate p, const T& new_value );	(2)

Replaces all elements satisfying specific criteria with new_value in the range [first, last). The first version replaces the elements that are equal to old_value, the second version replaces elements for which predicate p returns true.

Parameters

first, last	-	the range of elements to process
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 ForwardIterator can be dereferenced and then implicitly converted to Type. ​
new_value	-	the value to use as replacement

Return value

(none)

Complexity

Exactly last - first applications of the predicate.

Possible implementation

First version
template<class ForwardIterator, class T> void replace(ForwardIterator first, ForwardIterator last, const T& old_value, const T& new_value) { for (; first != last; ++first) { if (*first == old_value) { *first = new_value; } } }
Second version
template<class ForwardIterator, class UnaryPredicate, class T> void replace_if(ForwardIterator first, ForwardIterator last, UnaryPredicate p, const T& new_value) { for (; first != last; ++first) { if(p(*first)) { *first = new_value; } } }

Example

The following code at first replaces all occurrences of 8 with 88 in a vector of integers. Then it replaces all values less than 5 with 55.

#include <algorithm>
#include <array>
#include <iostream>
#include <functional>
 
int main()
{
    std::array<int, 10> s{5, 7, 4, 2, 8, 6, 1, 9, 0, 3};
 
    std::replace(s.begin(), s.end(), 8, 88);
 
    for (int a : s) {
        std::cout << a << " ";
    }
    std::cout << '\n';
 
    std::replace_if(s.begin(), s.end(), 
                    std::bind(std::less<int>(), std::placeholders::_1, 5), 55);
    for (int a : s) {
        std::cout << a << " ";
    }
    std::cout << '\n';
}

Output:

5 7 4 2 88 6 1 9 0 3
5 7 55 55 99 6 55 9 55 55

See also

replace_copy replace_copy_if	copies a range, replacing elements satisfying specific criteria with another value (function template)