@frozen
public struct NormalDistribution<T: BinaryFloatingPoint>: RandomDistribution
where T.RawSignificand: FixedWidthInteger선언
public let mean: T선언
public let standardDeviation: T선언
public init(mean: T = 0, standardDeviation: T = 1)선언
public func next<G>(using rng: inout G) -> T where G : RandomNumberGenerator