std::string::replace_copy(), std::string::replace_copy_if in C++
replace_copy
replace_copy() is a combination of copy() and replace().
- It copies the elements in the range [first, last) to the range beginning at result, replacing the appearances of old_value by new_value.
- The range copied is [first, last), which contains all the elements between first and last, including the element pointed by first but not the element pointed by last.
- The ranges shall not overlap in such a way that result points to an element in the range [first, last).
- The function uses operator== to compare the individual elements to old_value.
template <class InputIterator, class OutputIterator, class T> OutputIterator replace_copy (InputIterator first, InputIterator last, OutputIterator result, const T& old_value, const T& new_value); first, last : Input iterators to the initial and final positions in a sequence. old_value : Value to be replaced. new_value : Replacement value. Returns the position after the last copied element in the destination range (the first element that is not overwritten).
CPP
// CPP to illustrate // replace_copy #include <iostream> #include <vector> #include <algorithm> using namespace std; // Function to replace 'A' at v.begin() with Z and copy it // to v.begin() position void replace_copyDemo(vector< char >& v) { replace_copy(v.begin(), v.begin()+1, v.begin(), 'A' , 'Z' ); } // Function to print content of vector void print(vector< char >& v) { int len = v.size(); for ( int i = 0; i < len; i++) cout << v[i] << " " ; cout << endl; } // Driver code int main() { vector< char > v; for ( int i = 0; i <= 6; i++) v.push_back( 'A' + i); cout << "Before replace_copy " << ": " ; print(v); replace_copyDemo(v); cout << "After replace_copy " << ": " ; print(v); return 0; } |
Output:
Before replace_copy : A B C D E F G After replace_copy : Z B C D E F G
replace_copy_if
replace_copy_if() is a combination of copy() and replace_if().
- Copies the elements in the range [first, last) to the range beginning at result, replacing those for which pred returns true by new_value.
- In simpler terms, it Copies the elements of a sequence to another same-size sequence replacing any elements that satisfies a predicate, with another value.
- Returns the position after the last copied element in the destination range (the first element that is not overwritten).
Template <class InputIterator, class OutputIterator, class UnaryPredicate, class T> OutputIterator replace_copy_if (InputIterator first, InputIterator last, OutputIterator result, UnaryPredicate pred, const T& new_value); first, last : Input iterators to the initial and final positions in a sequence. old_value : Value to be replaced. new_value : Replacement value. pred : Unary function that accepts an element in the range as argument, and returns a value convertible to bool. The value returned indicates whether the element is to be replaced in the copy (if true, it is replaced).
CPP
// CPP code to illustrate // replace_copy_if #include <iostream> #include <algorithm> #include <vector> using namespace std; // Function to check if number is even int IsEven( int i) { return ((i % 2) == 0); } // Function to print content of vector void print(vector< int >& v) { int len = v.size(); for ( int i = 0; i < len; i++) cout << v[i] << " " ; cout << endl; } // Function to replace all // even numbers from vector v1 and // copying them to v2 void replace_copy_ifDemo(vector< int >& v1, vector< int >& v2) { replace_copy_if(v1.begin(), v1.end(), v2.begin(), IsEven, 0); } // Driver Code int main() { vector< int > v1, v2; for ( int i = 1; i <= 10; i++) v1.push_back(i); cout << "Before replace_copy_if : " ; print(v1); v2.resize(v1.size()); // allocate space replace_copy_ifDemo(v1, v2); cout << "After replace_copy_if : " ; print(v2); return 0; } |
Output:
Before replace_copy_if : 1 2 3 4 5 6 7 8 9 10 After replace_copy_if : 1 0 3 0 5 0 7 0 9 0
NOTE: Both algorithms i.e. replace_copy and replace_copy_if, returns the position after the last copied element in the destination range (the first element that is not overwritten).
Related Article : std::string::replace, std::string::replace_if
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