Assignment of data-member in read-only structure, class in STL set

Question

The minimal example of the problem I\'m having is reproduced below:

#include 
using namespace std;

class foo {
public:
  int value, x;
  foo(const in         


        

Answer 1

Objects in a set are immutable; if you want to modify an object, you need to:

1. make a copy of the object from the set,
2. modify the copy,
3. remove the original object from the set, and
4. insert the copy into the set

It will look something like this:

std::set s;
s.insert(1);

int x = *s.begin(); // (1)
x+= 1;              // (2)
s.erase(s.begin()); // (3)
s.insert(x);        // (4)