One Good Turn
Now, try FORWARD 80 TURN 2 / 5. This makes another five-sided figure. But it's not a pentagon; it's a five-sided "star polygon." The turtle crosses its path before returning to its starting position. The turtle makes two full turns while drawing the star polygon. In general, Numbers that can be represented as T / N are called rational numbers. So if the input to TURN is any rational number, then the turtle will eventually get back to its starting position, having drawn a figure with N points. Some numbers (such as the number of radians in a circle) can not be represented as T / N. If the turtle turns "irrationally," it will never return its starting position. Go to the next page or the previous page or the contents page. Mitchel Resnick and Brian Silverman Epistemology and Learning Group MIT Media Laboratory Last modified: 2/4/96
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