State machine where each state is represented by a function.

state_machine.c++

#include "state_machine.h"

#include <iostream>

using namespace std;

struct StateFn {
	State f;
	StateFn(State p) : f(p) {}
	operator State(void) { return f; }
};
using State = StateFn (*)(void);

StateFn EOF_state(void) {
	cout << "EOF State" << endl;
	return nullptr;
}
StateFn other_state(void) {
	cout << "Other State" << endl;
	return EOF_state;
}
StateFn normal_state(void) {
	cout << "Normal State" << endl;
	return other_state;
}

int main(void) {
	State state;
	state = normal_state();
	while (state != nullptr) {
		state = state();
	}
	cout << "FIN" << endl;
	return 0;
}

state_machine.h

#ifndef _STATE_MACHINE_H_
#define _STATE_MACHINE_H_
#pragma once

struct StateFn;
using State = StateFn (*)(void);

StateFn EOF_state(void);
StateFn other_state(void);
StateFn normal_state(void);

#endif // ! _STATE_MACHINE_H_