14.37 replace_if equal

#include <iostream>
#include <vector>
#include <algorithm>

class equ{
public:
    equ(int val) : value(val) {}
    bool operator()(int newval) {
        return newval == value;
    }
private:
    int value;
};

int main() {
    std::vector<int> v{1,2,3,4,5};
    equ a(3);
    std::replace_if(v.begin(), v.end(), a, 100);
    // or std::replace_if(v.begin(), v.end(), equ(3), 100);
    for (const auto &i:v) {
        std::cout << i << std::endl;
    }
}