Added JsonTextReader support for NaN, PositiveInfinity and NegativeInfinity constants.

Src/Newtonsoft.Json.Tests/JsonTextReaderTest.cs

@@ -215,5 +215,38 @@ namespace Newtonsoft.Json.Tests
 
       Assert.AreEqual(json, sb.ToString());
     }
+
+    [Test]
+    public void FloatingPointNonFiniteNumbers()
+    {
+      string input = @"[
+  NaN,
+  Infinity,
+  -Infinity
+]";
+
+      StringReader sr = new StringReader(input);
+
+      using (JsonReader jsonReader = new JsonTextReader(sr))
+      {
+        jsonReader.Read();
+        Assert.AreEqual(jsonReader.TokenType, JsonToken.StartArray);
+
+        jsonReader.Read();
+        Assert.AreEqual(jsonReader.TokenType, JsonToken.Float);
+        Assert.AreEqual(jsonReader.Value, double.NaN);
+
+        jsonReader.Read();
+        Assert.AreEqual(jsonReader.TokenType, JsonToken.Float);
+        Assert.AreEqual(jsonReader.Value, double.PositiveInfinity);
+
+        jsonReader.Read();
+        Assert.AreEqual(jsonReader.TokenType, JsonToken.Float);
+        Assert.AreEqual(jsonReader.Value, double.NegativeInfinity);
+
+        jsonReader.Read();
+        Assert.AreEqual(jsonReader.TokenType, JsonToken.EndArray);
+      }
+    }
   }
 }

Src/Newtonsoft.Json.Tests/JsonTextWriterTest.cs

@@ -172,5 +172,38 @@ namespace Newtonsoft.Json.Tests
         Assert.AreEqual(WriteState.Start, jsonWriter.WriteState);
       }
     }
+
+    [Test]
+    public void FloatingPointNonFiniteNumbers()
+    {
+      StringBuilder sb = new StringBuilder();
+      StringWriter sw = new StringWriter(sb);
+
+      using (JsonWriter jsonWriter = new JsonTextWriter(sw))
+      {
+        jsonWriter.Formatting = Formatting.Indented;
+
+        jsonWriter.WriteStartArray();
+        jsonWriter.WriteValue(double.NaN);
+        jsonWriter.WriteValue(double.PositiveInfinity);
+        jsonWriter.WriteValue(double.NegativeInfinity);
+        jsonWriter.WriteValue(float.NaN);
+        jsonWriter.WriteValue(float.PositiveInfinity);
+        jsonWriter.WriteValue(float.NegativeInfinity);
+        jsonWriter.WriteEndArray();
+      }
+
+      string expected = @"[
+  NaN,
+  Infinity,
+  -Infinity,
+  NaN,
+  Infinity,
+  -Infinity
+]";
+      string result = sb.ToString();
+
+      Assert.AreEqual(expected, result);
+    }
   }
 }

Src/Newtonsoft.Json/JavaScriptConvert.cs

@@ -65,6 +65,21 @@ namespace Newtonsoft.Json
     /// </summary>
     public static readonly string Undefined;
 
+    /// <summary>
+    /// Represents JavaScript's positive infinity as a string. This field is read-only.
+    /// </summary>
+    public static readonly string PositiveInfinity;
+
+    /// <summary>
+    /// Represents JavaScript's negative infinity as a string. This field is read-only.
+    /// </summary>
+    public static readonly string NegativeInfinity;
+
+    /// <summary>
+    /// Represents JavaScript's NaN as a string. This field is read-only.
+    /// </summary>
+    public static readonly string NaN;
+
     internal static long InitialJavaScriptDateTicks;
     internal static DateTime MinimumJavaScriptDate;
 
@@ -74,6 +89,9 @@ namespace Newtonsoft.Json
       False = "false";
       Null = "null";
       Undefined = "undefined";
+      PositiveInfinity = "Infinity";
+      NegativeInfinity = "-Infinity";
+      NaN = "NaN";
 
       InitialJavaScriptDateTicks = (new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc)).Ticks;
       MinimumJavaScriptDate = new DateTime(100, 1, 1);

Src/Newtonsoft.Json/JsonTextReader.cs

@@ -477,6 +477,18 @@ namespace Newtonsoft.Json
               throw new JsonReaderException("Unexpected end");
             }
             return true;
+          case 'N':
+            ParseNumberNaN();
+            return true;
+          case 'I':
+            ParseNumberPositiveInfinity();
+            return true;
+          case '-':
+            if (PeekNext() == 'I')
+              ParseNumberNegativeInfinity();
+            else
+              ParseNumber();
+            return true;
           case '/':
             ParseComment();
             return true;
@@ -738,6 +750,42 @@ namespace Newtonsoft.Json
       }
     }
 
+    private void ParseNumberNegativeInfinity()
+    {
+      if (MatchValue(JavaScriptConvert.NegativeInfinity, true))
+      {
+        SetToken(JsonToken.Float, double.NegativeInfinity);
+      }
+      else
+      {
+        throw new JsonReaderException("Error parsing negative infinity value.");
+      }
+    }
+
+    private void ParseNumberPositiveInfinity()
+    {
+      if (MatchValue(JavaScriptConvert.PositiveInfinity, true))
+      {
+        SetToken(JsonToken.Float, double.PositiveInfinity);
+      }
+      else
+      {
+        throw new JsonReaderException("Error parsing positive infinity value.");
+      }
+    }
+
+    private void ParseNumberNaN()
+    {
+      if (MatchValue(JavaScriptConvert.NaN, true))
+      {
+        SetToken(JsonToken.Float, double.NaN);
+      }
+      else
+      {
+        throw new JsonReaderException("Error parsing NaN value.");
+      }
+    }
+
     /// <summary>
     /// Changes the <see cref="State"/> to Closed. 
     /// </summary>