Merge pull request #5 from ordo-one/uniform-distribution

uniform distribution

Author: tayloraswift

Sources/Random/Uniform.swift

@@ -0,0 +1,27 @@
+import RealModule
+
+/// Uniform distribution implementation with stochastic rounding.
+@frozen public struct Uniform {
+    public let n: Int64
+    public let p: Double
+
+    @inlinable init(n: Int64, p: Double) {
+        self.n = n
+        self.p = p
+    }
+}
+extension Uniform {
+    /// Create a uniform distribution with the given parameters. Using values of ``p`` greater
+    /// than 0.5 is not recommended, as it could distort the mean of the distribution.
+    @inlinable public static subscript(n: Int64, p: Double) -> Self { .init(n: n, p: p) }
+}
+extension Uniform {
+    @inlinable public func sample(using generator: inout some RandomNumberGenerator) -> Int64 {
+        let n: Double = .init(self.n)
+        let x: Double = .random(in: 0 ... 2 * n * self.p, using: &generator)
+        let i: Int64 = .init(x)
+        let f: Double = x - Double.init(i)
+        let r: Int64 = Double.random(in: 0 ..< 1, using: &generator) < f ? 1 : 0
+        return min(self.n, i + r)
+    }
+}