Random i64 in [start, end): start + random for a random below the range length, drawn as the u64 sampler draws.
i64
[start, end)
start + random
unless both are bigints in [-2^63, 2^63 - 1], start < end, and end - start fits i64 (the reference's arithmetic).
bigint
[-2^63, 2^63 - 1]
start < end
end - start
Random
i64in[start, end):start + randomfor a random below the range length, drawn as the u64 sampler draws.