vector-set! - modify an element of a vector
(import (rnrs)) ;R6RS
(import (rnrs base)) ;R6RS
(import (scheme r5rs)) ;R7RS
(import (scheme base)) ;R7RS
(vector-set! vector k obj)
Constants in the source code are not supposed to be modified by the
program, but programs may still be able to do so. A compiler that
creates executable files can place the constants in read-only pages,
where the processor will automatically report attempts to mutate them.
Interpreters and online compilers normally skip this step and tend to
not detect mutation of constants. Implementations can also mark a
vector as immutable using various strategies like special memory
ranges, a special immutable vector tag or an immutable bit next to the
Implementations may also do different things in different modes, so
just testing at the REPL is not a reliable method to check if
constants are always mutable or not in a particular implementation.
Returns unspecified values.
Returns an unspecified value.
(let ((vec (vector 0 '(2 2 2 2) "Anna")))
(vector-set! vec 1 '("Sue" "Sue"))
=> #(0 ("Sue" "Sue") "Anna")
;; This example shows mutation of a constant vector. Constants are
;; allowed to be immutable, but implementations do not always check
;; this. It should raise an &assertion exception.
(vector-set! '#(0 1 2) 1 "doe")
; should raise &assertion exception
The specification of vectors does not actually require constant access
time, but in practice they are always implemented as flat arrays.
Therefore this procedure is used in algorithms that perform
random-access operations on arrays. Such algorithms would not have the
same time complexity if lists were used instead.
This procedure works the same everywhere.
This procedure can raise exceptions with the following condition types:
- &assertion (R6RS)
The wrong number of arguments was passed or an argument was outside its domain.
should be a mutable vector, and
must be an exact nonnegative integer less than the length of
The assertions described above are errors.
Implementations may signal an error, extend the procedure's
domain of definition to include such arguments,
or fail catastrophically.
This procedure first appeared in R2RS, where the vector notation was
This page is part of the
It includes materials from the RnRS documents.
More information can be found at
Programs should not modify constants.
Markup created by unroff 1.0sc, March 04, 2023.