Merge pull request #2452 from Hixie/unsimulatable

Remove Simulatable and restyle simulation_group.dart

packages/newton/lib/src/simulation.dart

@@ -4,20 +4,18 @@
 
 import 'tolerance.dart';
 
-abstract class Simulatable {
-  /// The current position of the object in the simulation
-  double x(double time);
-
-  /// The current velocity of the object in the simulation
-  double dx(double time);
-}
-
 /// The base class for all simulations. The user is meant to instantiate an
 /// instance of a simulation and query the same for the position and velocity
 /// of the body at a given interval.
-abstract class Simulation implements Simulatable {
+abstract class Simulation {
   Tolerance tolerance = toleranceDefault;
 
+  /// The current position of the object in the simulation
+  double x(double time);
+
+  /// The current velocity of the object in the simulation
+  double dx(double time); // TODO(ianh): remove this; see https://github.com/flutter/flutter/issues/2092
+
   /// Returns if the simulation is done at a given time
   bool isDone(double time);
 }

packages/newton/lib/src/simulation_group.dart

@@ -10,7 +10,8 @@ import 'utils.dart';
 /// must implement the appropriate methods to select the appropriate simulation
 /// at a given time interval. The simulation group takes care to call the `step`
 /// method at appropriate intervals. If more fine grained control over the the
-/// step is necessary, subclasses may override `Simulatable` methods.
+/// step is necessary, subclasses may override the [x], [dx], and [isDone]
+/// methods.
 abstract class SimulationGroup extends Simulation {
 
   /// The currently active simulation

packages/newton/lib/src/spring_simulation.dart

@@ -7,120 +7,154 @@ import 'dart:math' as math;
 import 'simulation.dart';
 import 'utils.dart';
 
-abstract class _SpringSolution implements Simulatable {
-  factory _SpringSolution(
-      SpringDescription desc, double initialPosition, double initialVelocity) {
-    double cmk =
-        desc.damping * desc.damping - 4 * desc.mass * desc.springConstant;
+enum SpringType { unknown, criticallyDamped, underDamped, overDamped }
 
-    if (cmk == 0.0) {
+abstract class _SpringSolution {
+  factory _SpringSolution(
+    SpringDescription desc,
+    double initialPosition,
+    double initialVelocity
+  ) {
+    double cmk = desc.damping * desc.damping - 4 * desc.mass * desc.springConstant;
+    if (cmk == 0.0)
       return new _CriticalSolution(desc, initialPosition, initialVelocity);
-    } else if (cmk > 0.0) {
+    if (cmk > 0.0)
       return new _OverdampedSolution(desc, initialPosition, initialVelocity);
-    } else {
-      return new _UnderdampedSolution(desc, initialPosition, initialVelocity);
-    }
-
-    return null;
+    return new _UnderdampedSolution(desc, initialPosition, initialVelocity);
   }
 
+  double x(double time);
+  double dx(double time);
   SpringType get type;
 }
 
 class _CriticalSolution implements _SpringSolution {
-  final double _r, _c1, _c2;
-
   factory _CriticalSolution(
-      SpringDescription desc, double distance, double velocity) {
+    SpringDescription desc,
+    double distance,
+    double velocity
+  ) {
     final double r = -desc.damping / (2.0 * desc.mass);
     final double c1 = distance;
     final double c2 = velocity / (r * distance);
     return new _CriticalSolution.withArgs(r, c1, c2);
   }
 
-  SpringType get type => SpringType.criticallyDamped;
-
   _CriticalSolution.withArgs(double r, double c1, double c2)
-      : _r = r,
-        _c1 = c1,
-        _c2 = c2;
+    : _r = r,
+      _c1 = c1,
+      _c2 = c2;
 
-  double x(double time) => (_c1 + _c2 * time) * math.pow(math.E, _r * time);
+  final double _r, _c1, _c2;
+
+  double x(double time) {
+    return (_c1 + _c2 * time) * math.pow(math.E, _r * time);
+  }
 
   double dx(double time) {
     final double power = math.pow(math.E, _r * time);
     return _r * (_c1 + _c2 * time) * power + _c2 * power;
   }
+
+  SpringType get type => SpringType.criticallyDamped;
 }
 
 class _OverdampedSolution implements _SpringSolution {
-  final double _r1, _r2, _c1, _c2;
-
   factory _OverdampedSolution(
-      SpringDescription desc, double distance, double velocity) {
-    final double cmk =
-        desc.damping * desc.damping - 4 * desc.mass * desc.springConstant;
-
+    SpringDescription desc,
+    double distance,
+    double velocity
+  ) {
+    final double cmk = desc.damping * desc.damping - 4 * desc.mass * desc.springConstant;
     final double r1 = (-desc.damping - math.sqrt(cmk)) / (2.0 * desc.mass);
     final double r2 = (-desc.damping + math.sqrt(cmk)) / (2.0 * desc.mass);
     final double c2 = (velocity - r1 * distance) / (r2 - r1);
     final double c1 = distance - c2;
-
     return new _OverdampedSolution.withArgs(r1, r2, c1, c2);
   }
 
   _OverdampedSolution.withArgs(double r1, double r2, double c1, double c2)
-      : _r1 = r1,
-        _r2 = r2,
-        _c1 = c1,
-        _c2 = c2;
+    : _r1 = r1,
+      _r2 = r2,
+      _c1 = c1,
+      _c2 = c2;
 
-  SpringType get type => SpringType.overDamped;
+  final double _r1, _r2, _c1, _c2;
 
-  double x(double time) =>
-      (_c1 * math.pow(math.E, _r1 * time) + _c2 * math.pow(math.E, _r2 * time));
+  double x(double time) {
+    return _c1 * math.pow(math.E, _r1 * time) +
+           _c2 * math.pow(math.E, _r2 * time);
+  }
+
+  double dx(double time) {
+    return _c1 * _r1 * math.pow(math.E, _r1 * time) +
+           _c2 * _r2 * math.pow(math.E, _r2 * time);
+  }
 
-  double dx(double time) => (_c1 * _r1 * math.pow(math.E, _r1 * time) +
-      _c2 * _r2 * math.pow(math.E, _r2 * time));
+  SpringType get type => SpringType.overDamped;
 }
 
 class _UnderdampedSolution implements _SpringSolution {
-  final double _w, _r, _c1, _c2;
-
   factory _UnderdampedSolution(
-      SpringDescription desc, double distance, double velocity) {
+    SpringDescription desc,
+    double distance,
+    double velocity
+  ) {
     final double w = math.sqrt(4.0 * desc.mass * desc.springConstant -
-            desc.damping * desc.damping) /
-        (2.0 * desc.mass);
+                     desc.damping * desc.damping) / (2.0 * desc.mass);
     final double r = -(desc.damping / 2.0 * desc.mass);
     final double c1 = distance;
     final double c2 = (velocity - r * distance) / w;
-
     return new _UnderdampedSolution.withArgs(w, r, c1, c2);
   }
 
   _UnderdampedSolution.withArgs(double w, double r, double c1, double c2)
-      : _w = w,
-        _r = r,
-        _c1 = c1,
-        _c2 = c2;
+    : _w = w,
+      _r = r,
+      _c1 = c1,
+      _c2 = c2;
 
-  SpringType get type => SpringType.underDamped;
+  final double _w, _r, _c1, _c2;
 
-  double x(double time) => math.pow(math.E, _r * time) *
-      (_c1 * math.cos(_w * time) + _c2 * math.sin(_w * time));
+  double x(double time) {
+    return math.pow(math.E, _r * time) *
+           (_c1 * math.cos(_w * time) + _c2 * math.sin(_w * time));
+  }
 
   double dx(double time) {
     final double power = math.pow(math.E, _r * time);
     final double cosine = math.cos(_w * time);
     final double sine = math.sin(_w * time);
-
-    return power * (_c2 * _w * cosine - _c1 * _w * sine) +
-        _r * power * (_c2 * sine + _c1 * cosine);
+    return      power * (_c2 * _w * cosine - _c1 * _w * sine) +
+           _r * power * (_c2 *      sine   + _c1 *      cosine);
   }
+
+  SpringType get type => SpringType.underDamped;
 }
 
 class SpringDescription {
+  SpringDescription({
+    this.mass,
+    this.springConstant,
+    this.damping
+  }) {
+    assert(mass != null);
+    assert(springConstant != null);
+    assert(damping != null);
+  }
+
+  /// Create a spring given the mass, spring constant and the damping ratio. The
+  /// damping ratio is especially useful trying to determing the type of spring
+  /// to create. A ratio of 1.0 creates a critically damped spring, > 1.0
+  /// creates an overdamped spring and < 1.0 an underdamped one.
+  SpringDescription.withDampingRatio({
+    double mass,
+    double springConstant,
+    double ratio: 1.0
+  }) : mass = mass,
+       springConstant = springConstant,
+       damping = ratio * 2.0 * math.sqrt(mass * springConstant);
+
   /// The mass of the spring (m)
   final double mass;
 
@@ -131,41 +165,23 @@ class SpringDescription {
   /// Not to be confused with the damping ratio. Use the separate
   /// constructor provided for this purpose
   final double damping;
-
-  SpringDescription(
-      { this.mass, this.springConstant, this.damping }
-  ) {
-    assert(mass != null);
-    assert(springConstant != null);
-    assert(damping != null);
-  }
-
-  /// Create a spring given the mass, spring constant and the damping ratio. The
-  /// damping ratio is especially useful trying to determing the type of spring
-  /// to create. A ratio of 1.0 creates a critically damped spring, > 1.0
-  /// creates an overdamped spring and < 1.0 an underdamped one.
-  SpringDescription.withDampingRatio(
-      {double mass, double springConstant, double ratio: 1.0})
-      : mass = mass,
-        springConstant = springConstant,
-        damping = ratio * 2.0 * math.sqrt(mass * springConstant);
 }
 
-enum SpringType { unknown, criticallyDamped, underDamped, overDamped, }
-
 /// Creates a spring simulation. Depending on the spring description, a
 /// critically, under or overdamped spring will be created.
 class SpringSimulation extends Simulation {
-  final double _endPosition;
-
-  final _SpringSolution _solution;
-
   /// A spring description with the provided spring description, start distance,
   /// end distance and velocity.
   SpringSimulation(
-      SpringDescription desc, double start, double end, double velocity)
-      : this._endPosition = end,
-        _solution = new _SpringSolution(desc, start - end, velocity);
+    SpringDescription desc,
+    double start,
+    double end,
+    double velocity
+  ) : _endPosition = end,
+      _solution = new _SpringSolution(desc, start - end, velocity);
+
+  final double _endPosition;
+  final _SpringSolution _solution;
 
   SpringType get type => _solution.type;
 
@@ -182,8 +198,12 @@ class SpringSimulation extends Simulation {
 /// A SpringSimulation where the value of x() is guaranteed to have exactly the
 /// end value when the simulation isDone().
 class ScrollSpringSimulation extends SpringSimulation {
-  ScrollSpringSimulation(SpringDescription desc, double start, double end, double velocity)
-    : super(desc, start, end, velocity);
+  ScrollSpringSimulation(
+    SpringDescription desc,
+    double start,
+    double end,
+    double velocity
+  ) : super(desc, start, end, velocity);
 
   double x(double time) => isDone(time) ? _endPosition : super.x(time);
 }