Circular Series of Values

Author: Patrick Philipot
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Here is a simple trick to obtain a repeated set of values from a series, from the first to the last, then wrapping back to the first again.

For example, if you have the days of the week stored as words in a block:

    days: [sunday monday tuesday wednesday thursday friday saturday]

The trick is quite simple. The first value is copied to the end of the block:

    day: first days
    append days day

Now you can call SELECT to get each of the next day values in order (without end):

    day: 'sunday
    repeat i 31 [
        print day: select days day
    ]

Why it Works

The SELECT function searches for a value, then returns the value that follows it. Putting the first value also at the end lets the SELECT function work for the saturday value, by finding sunday after it.