Use a feature array id to refer to a specific instance of a feature or to a range of feature instances. For example, if the feature "Circle1" were located in a while loop that looped five times, then five instances of the circle would exist upon exiting the loop. To refer to an individual instance of the five instances of "Circle1", use feature array syntax as described under "Feature Arrays:" where "Circle1[1]" would refer to the first instance, "Circle1[2]" would refer to the second instance, etc.
To refer to a range of instances use the .. notation. "Circle1[1..3]" refers to the 1st through 3rd instances of Circle1. "Circle1[3..5] refers to the 3rd through 5th instances of Circle1. "Circle1[1..5]" would refer to the 1st through 5th instances of Circle1. When a range of feature is referred to, the set is treated and behaves as a constructed set.