A slightly webified version of the example from the Dart homepage: www.dartlang.org
View this code in DartPad: https://dartpad.dev/fae22cffa7b184b4d27cd96dd633a5af?null_safety=true
Based on an anonymous gist created by DartPad: https://gist.github.com/anonymous/fb763a4a770b5cdd896982e10ccf4118
| <!DOCTYPE html> | |
| <html> | |
| <head> | |
| <meta charset="utf-8"> | |
| <meta name="viewport" content="width=device-width, initial-scale=1.0"> | |
| <title>pi-monte-carlo</title> | |
| <script type="application/dart" src="main.dart"></script> | |
| </head> | |
| <body> | |
| <h1>π ≅ <span id="output">?</span></h1> | |
| </body> | |
| </html> |
| import 'dart:html'; | |
| import 'dart:math' show Random; | |
| // We changed 5 lines of code to make this sample nicer on | |
| // the web (so that the execution waits for animation frame, | |
| // the number gets updated in the DOM, and the program ends | |
| // after 500 iterations). | |
| Future<void> main() async { | |
| print('Compute π using the Monte Carlo method.'); | |
| var output = querySelector("#output"); | |
| await for (var estimate in computePi().take(500)) { | |
| print('π ≅ $estimate'); | |
| output?.text = estimate.toStringAsFixed(5); | |
| await window.animationFrame; | |
| } | |
| } | |
| /// Generates a stream of increasingly accurate estimates of π. | |
| Stream<double> computePi({int batch: 100000}) async* { | |
| var total = 0; | |
| var count = 0; | |
| while (true) { | |
| var points = generateRandom().take(batch); | |
| var inside = points.where((p) => p.isInsideUnitCircle); | |
| total += batch; | |
| count += inside.length; | |
| var ratio = count / total; | |
| // Area of a circle is A = π⋅r², therefore π = A/r². | |
| // So, when given random points with x ∈ <0,1>, | |
| // y ∈ <0,1>, the ratio of those inside a unit circle | |
| // should approach π / 4. Therefore, the value of π | |
| // should be: | |
| yield ratio * 4; | |
| } | |
| } | |
| Iterable<Point> generateRandom([int? seed]) sync* { | |
| final random = Random(seed); | |
| while (true) { | |
| yield Point(random.nextDouble(), random.nextDouble()); | |
| } | |
| } | |
| class Point { | |
| final double x, y; | |
| const Point(this.x, this.y); | |
| bool get isInsideUnitCircle => x * x + y * y <= 1; | |
| } |