Random-Sample is a Lisp library for something which is not nearly as simple as it sounds: reliably taking a random sample of a sequence.
Most of the time you will just use
(random-sample:random-sample (iota 100) 5) => (57 32 28 45 4)
The algorithm used for sampling without replacement is basically Vitter’s Algorithm D.
Sometimes you may want to use the algorithm at a lower level. You
don’t want the sample itself; you only want the indices. In this case,
you can directly use
map-random-below, which simply calls a provided
function on each index.
(map-random-below my-function 5 length)