Multiple distinct objects: Difference between revisions

=={{header|Scheme}}==

{{libheader|Scheme/SRFIs}}

There is a standard function make-list which makes a list of size n, but repeats its given value.

<pre>

sash[r7rs]> (define-record-type <a> (make-a x) a? (x get-x))

#<unspecified>

sash[r7rs]> (define l1 (make-list 5 (make-a 3)))

#<unspecified>

sash[r7rs]> (eq? (list-ref l1 0) (list-ref l1 1))

#t

</pre>

In SRFI 1, a function list-tabulate is provided which instead calls a function to create a fresh value each time.

<pre>

sash[r7rs]> (define l2 (list-tabulate 5 (lambda (i) (make-a i))))

#<unspecified>

sash[r7rs]> (eq? (list-ref l2 0) (list-ref l2 1))

#f

sash[r7rs]> (map get-x l2)

(0 1 2 3 4)

</pre>