Ranges are most frequently used with sequence combinators as a means of iterating over integers. For example,
3 10 [a..b] [ sqrt ] map
Computing the factorial of 100 with a descending range:
100 1 [a..b] product
A range can be converted into a concrete sequence using a word such as >array. In most cases this is unnecessary since ranges implement the sequence protocol already. It is necessary if a mutable sequence is needed, for use with words such as set-nth or map!.