In the last lesson, you learned how to read all lines of data from a file using a while-loop.

While loops are always funny, in that depending on conditions of your code, the loop may not be executed at all. For example, consider this:

x=5
while x < 5 do
...
...
end


Here the while-loop will never be entered, since x<5 is false, because x=5 just before the while-loop is encountered.

In our data reading loop, we had to set data = true before the while-loop, to get it started. Yes, while-loops need to be "primed" or they may not run. In the last lesson, setting data=true "primed" the while loop properly.

Wouldn't it be nice if there was a looping structure that always ran at least once, with no priming required? There is! It's called the repeat-until loop. Let's try it.

Move the mouse over a dotted box for more information.

Here, let's try using a repeat-until-loop, and keep reading line after line, until file_read returns a false?