g++ play

build.sh

clear && g++-10 a.cpp 

watch.sh

clear && fswatch -0 --latency 0.2 --recursive --format "%f##%p" --event Updated -e ".*" -i ".*cpp$" ./ | xargs -0 -n 2 ./build.sh 2>&1

run.sh

sudo clear && ./a.out && echo "" && echo "Program exit"

a.cpp

#include <iostream>
#include <map>
using namespace std;

class A {
public:
    A(int i):num(i){}

    operator bool() const {
        return false;
    }

    bool operator <(const A& b) const {
        return this->num < b.num;
    };

    int num=0;
};

int main() {
    map<A,string> conta;

    conta.emplace(2,"foo");
    conta.emplace(1,"one");
    cout << conta.size()<<endl;
    for(auto i : conta) {
        cout<<i.first.num
            <<","<<i.second <<endl;
    }

    return 0;
}