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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.

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

vector-ref vector k Scheme Procedure
scm_vector_ref vector k C Function
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 (see 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.

vector-set! vector k obj Scheme Procedure
scm_vector_set_x vector k obj C Function
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")

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

vector-move-left! vec1 start1 end1 vec2 start2 Scheme Procedure
scm_vector_move_left_x (vec1, start1, end1, vec2, start2) C Function
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.

vector-move-right! vec1 start1 end1 vec2 start2 Scheme Procedure
scm_vector_move_right_x (vec1, start1, end1, vec2, start2) C Function
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.