random

(random limit &optional random-state)

Returns a random number in the half-open interval [0, limit). The result type follows the limit: an integer limit yields an integer, a float limit yields a float (so (random 1) is always 0). Every backend draws from a pseudo-random generator inside the program — ThreadLocalRandom on the interpreter and JVM, a built-in generator on WASM — rather than from the host once per draw, which is what makes a draw cost a few nanoseconds. Where there is a host, that generator is seeded from its entropy once per run (WASI random_get in Preview 1, wasi:random under --component), so the sequence still differs on every run; a --no-wasi module has no host to ask and repeats one sequence unless it is seeded — see the clock and randomness guide. For unpredictable bytes use rontolisp:random-bytes, which is the entropy API. The optional random-state argument is accepted and ignored (evaluated for effect): no random-state objects exist here — make-random-state answers nil.