11.6. A more complicated example

Although the process of transforming functions into member functions is mechanical, there are some oddities. For example, after operates on two Time structures, not just one, and we can’t make both of them implicit. Instead, we have to invoke the function on one of them and pass the other as an argument.

Inside the function, we can refer to one of the them implicitly, but to access the instance variables of the other we continue to use dot notation.

bool Time::after (const Time& time2) const {
  if (hour > time2.hour) return true;
  if (hour < time2.hour) return false;

  if (minute > time2.minute) return true;
  if (minute < time2.minute) return false;

  if (second > time2.second) return true;
  return false;

To invoke this function:

if (doneTime.after (currentTime)) {
  cout << "The bread will be done after it starts." << endl;

You can almost read the invocation like English: “If the done-time is after the current-time, then…”

The active code below is another practical example using the after function. Feel free to modify the time that school gets out, and the time that the track meet starts, if you wish!

Create the Dog::is_older() function as it would be defined INSIDE of the Dog structure definition. This function checks if the current Dog is older than another Dog. The function is invoked on the current Dog.

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