#### 5.6.3 Vectors

Vectors are sequences of Scheme objects. Unlike lists, the length of a
vector, once the vector is created, cannot be changed. The advantage of
vectors over lists is that the time required to access one element of a vector
given its position (synonymous with index), a zero-origin number,
is constant, whereas lists have an access time linear to the position of the
accessed element in the list.

Vectors can contain any kind of Scheme object; it is even possible to
have different types of objects in the same vector. For vectors
containing vectors, you may wish to use arrays, instead. Note, too,
that vectors are the special case of one dimensional non-uniform arrays
and that most array procedures operate happily on vectors
(see Arrays).