// chronistic.h
struct Chronistic
{
Chronistic(int _seconds) : seconds(_seconds) {next(time(0));}
virtual bool operator()() = 0; // pure virtural, never call from c'tor or d'tor
private: int seconds;
protected:
bool trigger()
{
time_t now = time(0);
if (now > trigger_target) return next(now); // always true
else return false;
}
private:
time_t trigger_target;
bool next(time_t now) // must not be virtual, must not call anything virtual (it's used in the c'tor). Always returns true.
{
trigger_target=now+seconds;
return true;
}
};


// chronistic.cpp
#include <iostream>
#include <cstdlib>

#include <string>
#include "chronistic.h"


using namespace std;


struct MyChronFunction : Chronistic
{
MyChronFunction(int seconds) : Chronistic(seconds) {}
virtual bool operator()()
{
if (!trigger()) return false;
cout<<"Time to do something"<<endl;
return true;
}
};


int main(int argc, char *argv[])
{
MyChronFunction cronologic(90); // setup to execute every 90 seconds
while (true)
{
cronologic();
usleep(10); // prevents race condition
}

return EXIT_SUCCESS;
}