blob: 8817176408904fca45bcee39fb820dc4c1055f1e (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
|
(define-module (combinations)
#:export (combinations))
(define (combinations lst n)
"Return N length subsequences of elements from
LST."
(if (or (null? lst) (zero? n))
(if (zero? n)'(()) '())
(let loop ((lst lst) (result '()))
(if (null? lst)
result
(let ((next-lst (cdr lst)))
(loop next-lst
(append result
(map (lambda (combo)
(cons (car lst) combo))
(combinations next-lst
(1- n))))))))))
|
