randomBelow (Function)

Signature: randomBelow(n: int) -> Result<int, Error>

Description: A cryptographically-secure uniform random integer in [0, n), unbiased by rejection sampling. Returns Result<int, Error> when n is positive and Error otherwise.

Parameters

• n (int): Exclusive upper bound; must be positive

Returns: Result<int, Error>

Example

let d = randomBelow(6) ?: 0  // a fair die face 0..5

d =
    match randomBelow 6
        Success value => value  // a fair die face 0..5
        Error message => 0