Implement Double.{toString, toStringAsExponential, toStringAsPrecision}

runtime/lib/double.cc

Index: runtime/lib/double.cc
diff --git a/runtime/lib/double.cc b/runtime/lib/double.cc
index 00c68e823af1033d676c8ada5744f8cd8eaa93b8..bd7eac50de1e52a95f2e65c38bded225530b4a42 100644
--- a/runtime/lib/double.cc
+++ b/runtime/lib/double.cc
@@ -189,10 +189,12 @@ DEFINE_NATIVE_ENTRY(Double_toStringAsFixed, 2) {
   const Double& arg = Double::CheckedHandle(arguments->At(0));
   GET_NATIVE_ARGUMENT(Smi, fraction_digits, arguments->At(1));
   double d = arg.value();
-  int fraction_digits_value = fraction_digits.Value();
   String& result = String::Handle();
-  bool succeeded = DoubleToStringAsFixed(d, fraction_digits_value, result);
-  if (!succeeded) {
+  intptr_t fraction_digits_value = fraction_digits.Value();
+  if (0 <= fraction_digits_value && fraction_digits_value <= 20) {
+    result = DoubleToStringAsFixed(d, static_cast<int>(fraction_digits_value));
+  }
+  if (result.IsNull()) {
     GrowableArray<const Object*> args;
     args.Add(&String::ZoneHandle(String::New(
         "Illegal arguments to double.toStringAsFixed")));
@@ -203,12 +205,41 @@ DEFINE_NATIVE_ENTRY(Double_toStringAsFixed, 2) {
 
 
 DEFINE_NATIVE_ENTRY(Double_toStringAsExponential, 2) {
-  UNIMPLEMENTED();
+  const Double& arg = Double::CheckedHandle(arguments->At(0));
+  GET_NATIVE_ARGUMENT(Smi, fraction_digits, arguments->At(1));
+  double d = arg.value();
+  String& result = String::Handle();
+  intptr_t fraction_digits_value = fraction_digits.Value();
+  if (-1 <= fraction_digits_value && fraction_digits_value <= 20) {
+    result =
+        DoubleToStringAsExponential(d, static_cast<int>(fraction_digits_value));
+  }
+  if (result.IsNull()) {
+    GrowableArray<const Object*> args;
+    args.Add(&String::ZoneHandle(String::New(
+        "Illegal arguments to double.toStringAsExponential")));
+    Exceptions::ThrowByType(Exceptions::kIllegalArgument, args);
+  }
+  arguments->SetReturn(result);
 }
 
 
 DEFINE_NATIVE_ENTRY(Double_toStringAsPrecision, 2) {
-  UNIMPLEMENTED();
+  const Double& arg = Double::CheckedHandle(arguments->At(0));
+  GET_NATIVE_ARGUMENT(Smi, precision, arguments->At(1));
+  double d = arg.value();
+  String& result = String::Handle();
+  intptr_t precision_value = precision.Value();
+  if (1 <= precision_value && precision_value <= 21) {
+    result = DoubleToStringAsPrecision(d, static_cast<int>(precision_value));
+  }
+  if (result.IsNull()) {
+    GrowableArray<const Object*> args;
+    args.Add(&String::ZoneHandle(String::New(
+        "Illegal arguments to double.toStringAsPrecision")));
+    Exceptions::ThrowByType(Exceptions::kIllegalArgument, args);
+  }
+  arguments->SetReturn(result);
 }