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An "array" is composed of an arbitrary number of other Lisp objects,
arranged in a contiguous block of memory. Any element of an array may
be accessed in constant time. In contrast, accessing an element of a
list requires time proportional to the position of the element in the
list. (Elements at the end of a list take longer to access than
elements at the beginning of a list.)
Emacs defines two types of array, strings and vectors. A string is
an array of characters and a vector is an array of arbitrary objects.
Both are one-dimensional. (Most other programming languages support
multidimensional arrays, but we don't think they are essential in Emacs
Lisp.) Each type of array has its own read syntax; see Note: String
Type, and Note: Vector Type.
An array may have any length up to the largest integer; but once
created, it has a fixed size. The first element of an array has index
zero, the second element has index 1, and so on. This is called
"zero-origin" indexing. For example, an array of four elements has
indices 0, 1, 2, and 3.
The array type is contained in the sequence type and contains both
strings and vectors.
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