A café's till exports the number of coffees sold each day as one long list. It always holds whole weeks, and every week starts on Monday: Monday, Tuesday, and so on up to Sunday, then the next Monday.
The manager wants to compare the same day across weeks, such as every Monday.
Task: write weekday_values(daily, weekday). weekday is a number for the day: 0 is Monday, 1 is Tuesday, and so on up to 6 for Sunday. Return that day's count from every week, as a plain list, in week order.
The list always holds at least one whole week, and its length is always a multiple of 7.