Move Rectangle and Point into dart:math.

sdk/lib/math/point.dart

+// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+part of dart.math;
+
+/**
+ * A utility class for representing two-dimensional positions.
+ */
+class Point<T extends num> {
+  final T x;
+  final T y;
+
+  const Point([T x = 0, T y = 0]): this.x = x, this.y = y;
+
+  String toString() => '($x, $y)';

[Lasse Reichstein Nielsen, 2013/10/03 06:24:03]

I wouldn't mind it saying "Point($x, $y)".
Just the "pretty" point syntax is indistinguishable from a two-element iterable.

[Emily Fortuna, 2013/10/03 21:29:12]

Done.

+
+  bool operator ==(other) {
+    if (other is !Point) return false;
+    return x == other.x && y == other.y;
+  }
+
+  int get hashCode => _JenkinsSmiHash.hash2(x.hashCode, y.hashCode);
+
+  Point<T> operator +(Point<T> other) {

[Lasse Reichstein Nielsen, 2013/10/03 06:24:03]

These are really Vector operations, not Point operations (it's not just
multiplication).
Needs documentation.

[Emily Fortuna, 2013/10/03 21:29:12]

Done.

+    return new Point<T>(x + other.x, y + other.y);
+  }
+
+  Point<T> operator -(Point<T> other) {
+    return new Point<T>(x - other.x, y - other.y);
+  }
+
+  /**
+   * Scale this point by [factor] as if it were a vector.

[floitsch, 2013/10/03 09:33:50]

if it was a vector

[Emily Fortuna, 2013/10/03 21:29:12]

Done.

+   *
+   * *Important* *Note*: This function accepts a `num` as its argument only so
+   * that you can scale Point<double> objects by an `int` factor. Because the

[Lasse Reichstein Nielsen, 2013/10/03 06:24:03]

I don't particularly like this, but I guess it is inevitable.
The alternative is to do:
  if (factor is int && T == int) return new Point<int>(x*factor,y*factor)) 
  return new Point<double>(x * factor, y * factor);

Then we would have to do it everywhere, so operator+ would be
Point<num> operator+(Point<num> other) {
  num newX = x + other.x;
  num newY = y + other.y;
  if (T == int && newX is int && newY is int) {
    return new Point<int>(newX, newY);
  }
  return new Point<double>(newX, newY)
}

That is - the num double-is-contagious behavior extended to Point.

[Emily Fortuna, 2013/10/03 21:29:12]

No Florian and I don't weren't thrilled with it either. :-( 

Why would we want to do that with +, too? I thought the point of distinguishing
Point<int> and Point<double> was so that you *couldn't* add a Point<double> to a
Point<int>?
(I can address whatever we decide in a follow up CL)

+   * star operator always returns the same type of Point that originally called
+   * it, passing in a double [factor] on a Point<int> _will_ _cause_ _a_

[Lasse Reichstein Nielsen, 2013/10/03 06:24:03]

`Point<int>`

[floitsch, 2013/10/03 09:33:50]

No use for future: _causes a runtime error_ in checked mode.

[Emily Fortuna, 2013/10/03 21:29:12]

Done.

[Emily Fortuna, 2013/10/03 21:29:12]

Done.

+   * _runtime_ _error_ in checked mode.
+   */
+  Point<T> operator *(num factor) {
+    return new Point<T>(x * factor, y * factor);
+  }
+
+  /**
+   * Get the straight line (Euclidean) distance between the origin (0, 0) and
+   * this point.
+   */
+  double get magnitude => sqrt(x * x + y * y);
+
+  /**
+   * Returns the distance between `this` and [other].
+   */
+  double distanceTo(Point<T> other) {
+    var dx = x - other.x;
+    var dy = y - other.y;
+    return sqrt(dx * dx + dy * dy);
+  }
+
+  /**
+   * Returns the squared distance between `this` and [other].
+   *
+   * Squared distances can be used for comparisons when the actual value is not
+   * required.
+   */
+  T squaredDistanceTo(Point<T> other) {
+    var dx = x - other.x;
+    var dy = y - other.y;
+    return dx * dx + dy * dy;
+  }
+

[Lasse Reichstein Nielsen, 2013/10/03 06:24:03]

Needs documentation.

[Emily Fortuna, 2013/10/03 21:29:12]

Done.

+  Point<int> ceil() => new Point<int>(x.ceil(), y.ceil());
+  Point<int> floor() => new Point<int>(x.floor(), y.floor());
+  Point<int> round() => new Point<int>(x.round(), y.round());
+
+  /**
+   * Truncates x and y to integers and returns the result as a new point.
+   */
+  Point<int> truncate() => new Point<int>(x.toInt(), y.toInt());
+}