SWI-Prolog -- randset/3

Availability::- use_module(library(random)).(can be autoloaded)

[det]randset(+K:int, +N:int, -S:list(int))

S is a sorted list of K unique random integers in the range 1..N. Implemented by enumerating 1..N and deciding whether or not the number should be part of the set. For example:

?- randset(5, 5, S).
S = [1, 2, 3, 4, 5].          (always)
?- randset(5, 20, S).
S = [2, 7, 10, 19, 20].

See also: randseq/3.
bug: Slow if N is large and K is small.