AnimatableVectorTest.swift

import SwiftUI
import enum Accelerate.vDSP

struct RootView: View {
    @State private var vector: AnimatableVector = .zero
    @State private var index: Int = 0

    let vectorArray: [AnimatableVector] = [
        .zero,
        AnimatableVector(values: [50, 100, 75, 100]),
        AnimatableVector(values: [100, 200, 100, 0])
    ]

    var body: some View {
        VStack {
            LineChart(vector: vector)
                .stroke(Color.red)
                .animation(Animation.default, value: vector)
//                .animation(Animation.spring(), value: vector) // Only first element of vector will animate
        }
        .contentShape(Rectangle())
        .onTapGesture(count: 1) {
            if index + 1 < vectorArray.count { index += 1 }
            else { index = 0 }
            vector = vectorArray[index]
        }
    }
}

struct LineChart: Shape {
    var vector: AnimatableVector

    var animatableData: AnimatableVector {
        get { vector }
        set { vector = newValue }
    }

    func path(in rect: CGRect) -> Path {
        Path { path in
            let xStep = rect.width / CGFloat(vector.values.count)
            var currentX: CGFloat = xStep
            path.move(to: .zero)

            vector.values.forEach {
                path.addLine(to: CGPoint(x: currentX, y: CGFloat($0)))
                currentX += xStep
            }
        }
    }
}

struct AnimatableVector: VectorArithmetic {
    static var zero = AnimatableVector(values: [0.0])

    static func + (lhs: AnimatableVector, rhs: AnimatableVector) -> AnimatableVector {
        let count = min(lhs.values.count, rhs.values.count)
        return AnimatableVector(values: vDSP.add(lhs.values[0..<count], rhs.values[0..<count]))
    }

    static func += (lhs: inout AnimatableVector, rhs: AnimatableVector) {
        let count = min(lhs.values.count, rhs.values.count)
        vDSP.add(lhs.values[0..<count], rhs.values[0..<count], result: &lhs.values[0..<count])
    }

    static func - (lhs: AnimatableVector, rhs: AnimatableVector) -> AnimatableVector {
        let count = min(lhs.values.count, rhs.values.count)
        return AnimatableVector(values: vDSP.subtract(lhs.values[0..<count], rhs.values[0..<count]))
    }

    static func -= (lhs: inout AnimatableVector, rhs: AnimatableVector) {
        let count = min(lhs.values.count, rhs.values.count)
        vDSP.subtract(lhs.values[0..<count], rhs.values[0..<count], result: &lhs.values[0..<count])
    }

    var values: [Double]

    mutating func scale(by rhs: Double) {
        values = vDSP.multiply(rhs, values)
    }

    var magnitudeSquared: Double {
        vDSP.sum(vDSP.multiply(values, values))
    }
}