replace

     Algorithm

Substitutes elements stored in a collection with new values.

Contents

• Synopsis
• Description
• Complexity
• Example
• Warning
• See Also

#include <algorithm>

template <class ForwardIterator, class T>
void replace (ForwardIterator first,
              ForwardIterator last,
              const T& old_value,
              const T& new_value);

The replace algorithm replaces elements referred to by iterator i in the range [first, last) with new_value when the following condition holds: *i == old_value

Exactly last - first comparisons or applications of the corresponding predicate are done.

//
// replace.cpp
//
 #include <algorithm>
 #include <vector>
 #include <iterator>
 #include <iostream.h>
 template<class Arg>
 struct all_true : public unary_function<Arg, bool>
 {
   bool operator()(const Arg&){ return 1; }
 };
 int main()
 {
   //Initialize a vector with an array of integers
   int arr[10] = {1,2,3,4,5,6,7,8,9,10};
   vector<int> v(arr, arr+10);
   //Print out original vector
   cout << "The original list: " << endl << "     ";
   copy(v.begin(),v.end(),ostream_iterator<int>(cout," "));
   cout << endl << endl;
   //Replace the number 7 with 11
   replace(v.begin(), v.end(), 7, 11);
   // Print out vector with 7 replaced, 
   // s.b. 1 2 3 4 5 6 11 8 9 10
   cout << "List after replace " << endl << "     ";
   copy(v.begin(),v.end(),ostream_iterator<int>(cout," "));
   cout << endl << endl;
   //Replace 1 2 3 with 13 13 13
   replace_if(v.begin(), v.begin()+3, all_true<int>(), 13);
   // Print out the remaining vector, 
   // s.b. 13 13 13 4 5 6 11 8 9 10
   cout << "List after replace_if " << endl << "     ";
   copy(v.begin(),v.end(),ostream_iterator<int>(cout," "));
   cout << endl << endl;
   return 0;
 }
Output :
The original list:
     1 2 3 4 5 6 7 8 9 10
List after replace:
     1 2 3 4 5 6 11 8 9 10
List after replace_if:
     13 13 13 4 5 6 11 8 9 10
List using replace_copy to cout:
     17 17 17 4 5 6 11 8 9 10
List with all elements output as 19s:
     19 19 19 19 19 19 19 19 19 19

If your compiler does not support default template parameters, then you need to always supply the Allocator template argument. For instance, you will need to write :

vector<int, allocator>

instead of :

vector<int>

replace_if, replace_copy, replace_copy_if