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E.2.1 In General

A Sequence is an Ordered Set of Elements

A “sequence” is a Lisp object that represents an ordered set of elements and is the union of two other Lisp types:

• lists and
• arrays

The common property that all sequences have is that each is an ordered collection of elements.

Sequence types share important similarities:

• all have a length L, and
• all have elements which can be indexed from zero to L minus one