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# (guile.info.gz) Vector Accessors Info Catalog (guile.info.gz) Vector Creation (guile.info.gz) Vectors
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22.3.3 Accessing and Modifying Vector Contents
----------------------------------------------

`vector-length' and `vector-ref' return information about a given
vector, respectively its size and the elements that are contained in
the vector.

-- Scheme Procedure: vector-length vector
-- C Function: scm_vector_length vector
Return the number of elements in VECTOR as an exact integer.

-- Scheme Procedure: vector-ref vector k
-- C Function: scm_vector_ref vector k
Return the contents of position K of VECTOR.  K must be a valid
index of VECTOR.
(vector-ref '#(1 1 2 3 5 8 13 21) 5) => 8
(vector-ref '#(1 1 2 3 5 8 13 21)
(let ((i (round (* 2 (acos -1)))))
(if (inexact? i)
(inexact->exact i)
i))) => 13

A vector created by one of the dynamic vector constructor procedures
( Vector Creation) can be modified using the following
procedures.

_NOTE:_ According to R5RS, it is an error to use any of these
procedures on a literally read vector, because such vectors should be
considered as constants.  Currently, however, Guile does not detect this
error.

-- Scheme Procedure: vector-set! vector k obj
-- C Function: scm_vector_set_x vector k obj
Store OBJ in position K of VECTOR.  K must be a valid index of
VECTOR.  The value returned by `vector-set!' is unspecified.
(let ((vec (vector 0 '(2 2 2 2) "Anna")))
(vector-set! vec 1 '("Sue" "Sue"))
vec) =>  #(0 ("Sue" "Sue") "Anna")

-- Scheme Procedure: vector-fill! v fill
-- C Function: scm_vector_fill_x (v, fill)
Store FILL in every position of VECTOR.  The value returned by
`vector-fill!' is unspecified.

-- Scheme Procedure: vector-move-left! vec1 start1 end1 vec2 start2
-- C Function: scm_vector_move_left_x (vec1, start1, end1, vec2,
start2)
Copy elements from VEC1, positions START1 to END1, to VEC2
starting at position START2.  START1 and START2 are inclusive
indices; END1 is exclusive.

`vector-move-left!' copies elements in leftmost order.  Therefore,
in the case where VEC1 and VEC2 refer to the same vector,
`vector-move-left!' is usually appropriate when START1 is greater
than START2.

-- Scheme Procedure: vector-move-right! vec1 start1 end1 vec2 start2
-- C Function: scm_vector_move_right_x (vec1, start1, end1, vec2,
start2)
Copy elements from VEC1, positions START1 to END1, to VEC2
starting at position START2.  START1 and START2 are inclusive
indices; END1 is exclusive.

`vector-move-right!' copies elements in rightmost order.
Therefore, in the case where VEC1 and VEC2 refer to the same
vector, `vector-move-right!' is usually appropriate when START1 is
less than START2.

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