std::replace, std::replace_if
From Cppreference
| Defined in header <algorithm>
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| template< class ForwardIterator, class T >
void replace( ForwardIterator first, ForwardIterator last, |
(1) | |
| template< class ForwardIterator, class UnaryPredicate, class T >
void replace_if( ForwardIterator first, ForwardIterator last, |
(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.
Contents |
[edit] 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:
The signature does not need to have const &, but the function must not modify the objects passed to it. |
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| new_value | - | the value to use as replacement | |||||||||
[edit] Return value
(none)
[edit] Complexity
Exactly last - first applications of the predicate.
[edit] Equivalent function
| First version |
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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; } } } |
[edit] 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
[edit] See also
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copies a range, replacing elements satisfying specific criteria with another value (function template) |
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