make-bytevector(3scm) Scheme Programmer's Manual make-bytevector(3scm)

make-bytevector - create a new bytevector 

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


(make-bytevector k)
(make-bytevector k fill)

Return a newly allocated bytevector of k bytes.

If the fill argument is missing, the initial contents of the returned bytevector are unspecified.

If the fill argument is present, it must be an exact integer object. Every byte in the returned bytevector will be set to this value.

R6RS
The fill argument must be in the range [−128, 255]. If fill is positive, it is interpreted as if passed to bytevector-u8-set!(3scm). If it is negative, it is instead used as if passed to bytevector-s8-set!(3scm).
R7RS
The fill argument must be in the range [0, 255].

Chez Scheme, Loko Scheme, (others?)
If k is zero then the empty bytevector object is returned.
GNU Guile, Loko Scheme, (others?)
If fill is missing then the bytevector is initialized to zeros.
Chibi Scheme
Even though Chibi is an R7RS implementation, the fill argument is interpreted as in R6RS. This is a valid extension of R7RS.

Returns a single object which is a bytevector object of the given length. If k is non-zero then the bytevector is fresh. If k is zero then the unique empty bytevector object may be returned. 

(make-bytevector 2 12)
    => #u8(12 12)          ;R7RS notation

This procedure is used in code that works with mutable bytevectors. For some code an alternative is to use open-bytevector-output-port(3scm) and to build the data sequentially.

Portable code should provide the second argument, and should keep it in the range [0, 255].

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.
&implementation-restriction (R6RS)
There is not enough free memory to hold the new bytevector.
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.

u8-list->bytevector(3scm)

R6RS, R7RS

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

It is often a mistake to call this procedure without the fill argument. Unusual values of k can stress the Scheme implementation's memory allocator and cause a crash.
2022-03-21