Fix string output for large integers

This fix makes calling String() on a JSON Number return the original value
as it was represented in the JSON document for signed and unsigned integers.
This ensures that very big (plus-53bit) integers are correctly returned.
Floating points maintain their previous behavior [-+]?[0-9]*\.?[0-9]*.

closes #74

gjson.go

@@ -77,7 +77,20 @@ func (t Result) String() string {
 	case False:
 		return "false"
 	case Number:
-		return strconv.FormatFloat(t.Num, 'f', -1, 64)
+		if len(t.Raw) == 0 {
+			// calculated result
+			return strconv.FormatFloat(t.Num, 'f', -1, 64)
+		}
+		var i int
+		if t.Raw[0] == '-' {
+			i++
+		}
+		for ; i < len(t.Raw); i++ {
+			if t.Raw[i] < '0' || t.Raw[i] > '9' {
+				return strconv.FormatFloat(t.Num, 'f', -1, 64)
+			}
+		}
+		return t.Raw
 	case String:
 		return t.Str
 	case JSON:
@@ -1288,7 +1301,7 @@ func parseArray(c *parseContext, i int, path string) (int, bool) {
 					if rp.alogok {
 						break
 					}
-					c.value.Raw = val
+					c.value.Raw = ""
 					c.value.Type = Number
 					c.value.Num = float64(h - 1)
 					c.calcd = true

gjson_test.go

@@ -479,7 +479,8 @@ func TestBasic4(t *testing.T) {
 	}
 	token = get(basicJSON, "arr.#")
 	if token.String() != "6" {
-		t.Fatal("expecting '6'", "got", token.String())
+		fmt.Printf("%#v\n", token)
+		t.Fatal("expecting 6", "got", token.String())
 	}
 	token = get(basicJSON, "arr.3.hello")
 	if token.String() != "world" {
@@ -1354,3 +1355,39 @@ null
 	}
 
 }
+
+func TestNumUint64String(t *testing.T) {
+	i := 9007199254740993 //2^53 + 1
+	j := fmt.Sprintf(`{"data":  [  %d, "hello" ] }`, i)
+	res := Get(j, "data.0")
+	if res.String() != "9007199254740993" {
+		t.Fatalf("expected '%v', got '%v'", "9007199254740993", res.String())
+	}
+}
+
+func TestNumInt64String(t *testing.T) {
+	i := -9007199254740993
+	j := fmt.Sprintf(`{"data":[ "hello", %d ]}`, i)
+	res := Get(j, "data.1")
+	if res.String() != "-9007199254740993" {
+		t.Fatalf("expected '%v', got '%v'", "-9007199254740993", res.String())
+	}
+}
+
+func TestNumBigString(t *testing.T) {
+	i := "900719925474099301239109123101" // very big
+	j := fmt.Sprintf(`{"data":[ "hello", "%s" ]}`, i)
+	res := Get(j, "data.1")
+	if res.String() != "900719925474099301239109123101" {
+		t.Fatalf("expected '%v', got '%v'", "900719925474099301239109123101", res.String())
+	}
+}
+
+func TestNumFloatString(t *testing.T) {
+	i := -9007199254740993
+	j := fmt.Sprintf(`{"data":[ "hello", %d ]}`, i) //No quotes around value!!
+	res := Get(j, "data.1")
+	if res.String() != "-9007199254740993" {
+		t.Fatalf("expected '%v', got '%v'", "-9007199254740993", res.String())
+	}
+}