Add a number to itself in C++ - c++

Question

Which is the simplest way to add a number to itself incrementally until some condition is reached? In the code bellow, we can calculate when an event will occur by simply adding event_occurence to itself until we reach max_events. I know it can be done with std::IOTA and vectors, but I want it to keep it to the simplest math possible.
My idea was to use: i=1, i * number to be multiplied, for i<=some value, i++. But only the first value gets incremented correctly.
int main()
{
int curent_year = 2021;
int input_year;
int event_occurence = 4;
std::cout << "When did you watch your first World Cup?" << std::endl;
std::cin >> input_year;
int max_events = (curent_year - input_year) / event_occurence;
int last_event = input_year + (max_events * event_occurence);
int next_first_event = input_year + event_occurence;
std::cout << "Next world cup was held in " << next_first_event << "... Meanwhile, another " << max_events << " world cups took place. The last world cup took place in " << last_event <<"." << std::endl;
int i=1;
int inbetween_events = input_year + i * event_occurence;
for (int i = 1; i <= max_events; i++)
std::cout << "The were also these worlds cups held in the following years: " <<inbetween_events <<std::endl;
}
code above compiled

Answer 1

int i=1;
int inbetween_events = input_year + i * event_occurence;
for (int i = 1; i <= max_events; i++)
std::cout << "The were also these worlds cups held in the following years: " <<inbetween_events <<std::endl;
}
Problem 1:
You're using a local variable (counted in CPU registers) with the same name function variable that is the parent of function for (...). You declare it in there by saying "int i = 1", what means "make new temp variable name i, value = 1)
Move the "calc"
int inbetween_events = input_year + i * event_occurence;
inside the function if you want to print out series of numbers (print inbetween_events = input_year + i * event_occurence;) , or make it
for (; i <= max_events; i++)
or
for (i = 1; i <= max_events; i++)
That could work, but I can't test it :P
You could change variables' names, but then it's still pretty ineffective, because you would increment one variable inside a loop, making 2 operations instead of one.
Problem 2:
You also don't increment the "inbetween_events" in the "for" loop.
You ask it to print out that variable "i" times. You initialized that variable as output of arithmetic operation, it wont change its value unless you order it to change it.

Answer 2

C++ doesn't store instructions and run them later when needed. It runs them right away. So, if you want to compute the in-between events at multiple dates, you need to code it this way:
for (int i = 1; i <= max_events; i++)
// compute inbetween_events for each value of i
int inbetween_events = input_year + i * event_occurence;
std::cout << "The were also these worlds cups held in the following years: " <<inbetween_events <<std::endl;
}
You'll probably want to fix the output with something like:
// output header first
std::cout << "The were also these worlds cups held in the following years: ";
for (int i = 1; i <= max_events; i++)
// compute inbetween_events for each value of i
int inbetween_events = input_year + i * event_occurence;
// output each year with a comma and space
std::cout << inbetween_events << ", ";
}
// end the line
std::cout << std::endl;