De Casteljau's algorithm implementation in Swift 5

Casteljau.swift

import CoreGraphics

class Casteljau {
    let count: Int
    let x: [CGFloat]
    let y: [CGFloat]
    var b: [[CGFloat]]

    init(p0: CGPoint, p1: CGPoint, p2: CGPoint, p3: CGPoint) {
        let points = [p0, p1, p2, p3]
        x = points.map(\.x)
        y = points.map(\.y)
        count = points.count

        let nanArray = Array(repeating: CGFloat.nan, count: count)
        b = Array(repeating: nanArray, count: count)
    }

    func point(at t: CGFloat) -> CGPoint {
        return .init(x: evaluate(t: t, initialValues: x),
                     y: evaluate(t: t, initialValues: y))
    }
}

private extension Casteljau {
    func initialize(_ initialValues: [CGFloat]) {
        for i in 0..<count {
            b[0][i] = initialValues[i]
        }
    }

    func evaluate(t: CGFloat, initialValues: [CGFloat]) -> CGFloat {
        initialize(initialValues)
        for j in 1..<count {
            for i in 0..<count-j {
                b[j][i] = b[j-1][i] * (1-t) + b[j-1][i+1] * t
            }
        }
        return b[count-1][0]
    }
}