Manual page for vector-ref(3scm)

vector-ref - access an element of a vector

LIBRARY

(import (rnrs))                     ;R6RS
(import (rnrs base))                ;R6RS
(import (scheme r5rs))              ;R7RS
(import (scheme base))              ;R7RS

SYNOPSIS

(vector-ref vector k)

DESCRIPTION

Returns the contents of element k of vector.

RETURN VALUES

Returns a single value; an object from the vector.

EXAMPLES

(vector-ref '#(1 1 2 3 5 8 13 21) 5)
        => 8

(vector-ref '#(1 1 2 3 5 8 13 21)
            (exact
             (round (* 2 (acos -1)))))
        => 13

APPLICATION USAGE

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.

COMPATIBILITY

This procedure works the same everywhere.

ERRORS

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. In particular, k must be an exact nonnegative integer less than the length of vector.
R7RS: 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.

STANDARDS

R4RS, IEEE Scheme, R5RS, R6RS, R7RS

HISTORY

This procedure first appeared in R2RS, where the vector notation was optional.

AUTHORS

This page is part of the scheme-manpages project. It includes materials from the RnRS documents. More information can be found at https://github.com/schemedoc/manpages/.

Markup created by unroff 1.0sc, March 04, 2023.