- Add a math library. Currently it mostly matches the Math class in dart:core.

lib/math/random.dart

+// Copyright (c) 2012, 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.
+
+// A part of the dart:math library.
+
+/**
+ * A random number generator. The default implementation supplies a stream of
+ * pseudo-random bits which is not suitable for cryptographic purposes.
+ */
+interface Random default _Random {
+  /** 
+   * Creates a random-number generator. The optional parameter [seed] is used
+   * to initialize the internal state of the generator. The implementation of
+   * the random stream can change between releases of the library.
+   *
+   * Implementation note: The default implementation uses up to 64-bits of seed.
+   */
+  Random([int seed]);
+
+  /** 
+   * Generates a positive random integer uniformly distributed on the range
+   * from 0, inclusive, to [max], exclusive.
+   *
+   * Implementation note: The default implementation supports [max] values
+   * between 1 and ((1<<32) - 1) inclusive.
+   */
+  int nextInt(int max);
+
+  /** 
+   * Generates a positive random floating point value uniformly distributed on
+   * the range from 0.0, inclusive, to 1.0, exclusive.
+   */
+  double nextDouble();
+
+  /** 
+   * Generates a random boolean value.
+   */
+  bool nextBool();
+}
+
+class _Random implements Random {
+
+  _Random([int seed = null]) {
+    if (seed == null) {
+      seed = _nextSeed();
+    }
+    do {
+      seed = (seed + 0x5A17) & _MASK_64;
+    } while (seed == 0);
+    _state = seed;
+  }
+
+  // The algorithm used here is Multiply with Carry (MWC) with a Base b = 2^32.
+  // http://en.wikipedia.org/wiki/Multiply-with-carry
+  // The constant A is selected from "Numerical Recipes 3rd Edition" p.348 B1.
+  int _nextInt32() {
+    _state = ((_A * (_state & _MASK_32)) + (_state >> 32)) & _MASK_64;
+    return _state & _MASK_32;
+  }
+
+  int nextInt(int max) {
+    if (max <= 0 || max > _POW2_32) {
+      throw new IllegalArgumentException("max must be positive and < 2^32:"
+                                         " $max");
+    }
+    if ((max & -max) == max) {
+      // Fast case for powers of two.
+      return _nextInt32() & (max - 1);
+    }
+    
+    var rnd32;
+    var result;
+    do {
+      rnd32 = _nextInt32();
+      result = rnd32 % max;
+    } while (rnd32 - result + max >= _POW2_32);
+    return result;
+  }
+
+  double nextDouble() {
+    return ((nextInt(1 << (26)) << 27) + nextInt(1 << 27)) / _POW2_53_D;
+  }
+
+  bool nextBool() {
+    return nextInt(1) == 0;
+  }
+
+  static final _MASK_32 = (1 << 32) - 1;
+  static final _MASK_64 = (1 << 64) - 1;
+  static final _POW2_32 = 1 << 32;
+  static final _POW2_53_D = 1.0 * (1 << 53);
+
+  static final _A = 0xffffda61;
+
+  var _state;
+
+  int _nextSeed() {
+    if (_prng == null) {
+      // TODO(iposva): Use system to get a random seed.
+      _prng = new _Random(new Date.now().value);
+    }
+    // Trigger the PRNG once to change the internal state.
+    _prng._nextInt32();
+    return _prng._state;
+  }
+
+  static var _prng = null;
+}