Issue #5: properly validate 001 number

validate.go

@@ -249,15 +249,15 @@ func validateNumber(s string) (string, error) {
 		}
 		i++
 	}
-	if i == 0 {
+	if i <= 0 {
 		return s, fmt.Errorf("expecting 0..9 digit, got %c", s[0])
 	}
-	if i >= len(s) {
-		return "", nil
-	}
 	if s[0] == '0' && i != 1 {
 		return s, fmt.Errorf("unexpected number starting from 0")
 	}
+	if i >= len(s) {
+		return "", nil
+	}
 	if s[i] == '.' {
 		// Validate fractional part
 		s = s[i+1:]

validate_test.go

@@ -99,6 +99,7 @@ func TestValidate(t *testing.T) {
 		"123.",
 		"123.345",
 		"001 ",
+		"001",
 
 		// object
 		"{}",