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try preceding the function definition with the keyword "inline"
that will prevent those duplicate symbol errors, particularly when the function definition is in a header file.



what the...

it should go somewhere after the class definition of heltal, but before the definition of generate_numbers, and must be in the global scope in your program, not inside a class.

post your code please.

you haven't defined a way for std:: ostream to print a heltal object. you need to define a function like this:


std::ostream& operator << (std::ostream& os, const heltal& rhs)
{
// the code...