Fraction class prototype and test (not to be committed).

runtime/lib/double.dart

Index: runtime/lib/double.dart
diff --git a/runtime/lib/double.dart b/runtime/lib/double.dart
index ade4b9317bcd75c3c5150c78372a803f8630516d..fd13bc42f1f4fca008a5269f3e2b57c7b6deb50a 100644
--- a/runtime/lib/double.dart
+++ b/runtime/lib/double.dart
@@ -6,6 +6,12 @@ class _Double implements double {
   factory _Double.fromInteger(int value)
       native "Double_doubleFromInteger";
 
+  factory _Double.fromFraction(fraction value) {
+    return _DoubleFromFraction(value._numerator, value._denominator);
+  }
+  static _Double _DoubleFromFraction(int numerator, int denominator)
+      native "Double_doubleFromFraction";
+
   Type get runtimeType => double;
 
   // TODO: Make a stared static method for hashCode and _identityHashCode
@@ -57,6 +63,7 @@ class _Double implements double {
   }
   bool _equal(double other) native "Double_equal";
   bool _equalToInteger(int other) native "Double_equalToInteger";
+  bool _equalToFraction(fraction other) => _equal(other.toDouble());
   bool operator <(num other) {
     return other > this;
   }
@@ -91,6 +98,31 @@ class _Double implements double {
   bool _greaterThanFromInteger(int other)
       native "Double_greaterThanFromInteger";
 
+  double _addFromFraction(fraction other) {
+    return new _Double.fromFraction(other)._add(this);
+  }
+  double _subFromFraction(fraction other) {
+    return new _Double.fromFraction(other)._sub(this);
+  }
+  double _mulFromFraction(fraction other) {
+    return new _Double.fromFraction(other)._mul(this);
+  }
+  double _divFromFraction(fraction other) {
+    return new _Double.fromFraction(other)._div(this);
+  }
+  int _truncDivFromFraction(fraction other) {
+    return new _Double.fromFraction(other)._trunc_div(this);
+  }
+  double _moduloFromFraction(fraction other) {
+    return new _Double.fromFraction(other)._modulo(this);
+  }
+  double _remainderFromFraction(fraction other) {
+    return new _Double.fromFraction(other)._remainder(this);
+  }
+  bool _greaterThanFromFraction(fraction other) {
+    return new _Double.fromFraction(other)._greaterThan(this);
+  }
+
   bool get isNegative native "Double_getIsNegative";
   bool get isInfinite native "Double_getIsInfinite";
   bool get isNaN native "Double_getIsNaN";
@@ -136,9 +168,21 @@ class _Double implements double {
   }
 
   int toInt() native "Double_toInt";
-  num _toBigintOrDouble() { return this; }
+  num _toBigintIfInteger() { return this; }
+  num _toDoubleOrFraction() { return this; }
   double toDouble() { return this; }
 
+  fraction toFraction() {
+    var fract = new List(2);
+    _DoubleToFraction(fract);
+    return new _Fraction(fract[0], fract[1]);
+  }
+  void _DoubleToFraction(List fract) native "Double_toFraction";
+
+  fraction toPercent() {
+    return new _Fraction((this*100).toInt(), 100);
+  }
+
   static const int CACHE_SIZE_LOG2 = 3;
   static const int CACHE_LENGTH = 1 << (CACHE_SIZE_LOG2 + 1);
   static const int CACHE_MASK = CACHE_LENGTH - 1;