From 86b5abde08507a498496e90fe1ca6981006078e8 Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Fri, 13 Apr 2012 11:15:08 +1000
Subject: [PATCH] Add json::null::as_null implementation

---
 json.cpp.rl | 5 +++++
 json.hpp    | 5 ++++-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/json.cpp.rl b/json.cpp.rl
index 6cc2ae58..b9896b4e 100644
--- a/json.cpp.rl
+++ b/json.cpp.rl
@@ -305,6 +305,11 @@ json::node::as_boolean (void) const
         { throw parse_error ("node is not a boolean"); }
 
 
+const json::null&
+json::node::as_null (void) const
+        { throw parse_error ("node is not a null"); }
+
+
 bool
 json::node::operator!=(const node &rhs) const
     { return !(*this == rhs); }
diff --git a/json.hpp b/json.hpp
index 54dec959..b7c2bf7a 100644
--- a/json.hpp
+++ b/json.hpp
@@ -55,6 +55,7 @@ namespace json {
             virtual const string&  as_string  (void) const;
             virtual const number&  as_number  (void) const;
             virtual const boolean& as_boolean (void) const;
+            virtual const null&    as_null    (void) const;
 
             virtual bool is_object  (void) const { return false; }
             virtual bool is_array   (void) const { return false; }
@@ -206,11 +207,13 @@ namespace json {
     /// Represents a JSON null value.
     class null : public node {
         public:
-            virtual bool is_null (void) const { return  true; }
             virtual bool operator==(const null&) const { return true; }
             virtual bool operator==(const node   &rhs) const
                 { return rhs == *this; }
 
+            virtual bool        is_null (void) const { return  true; }
+            virtual const null& as_null (void) const { return *this; }
+
             virtual std::ostream& write (std::ostream &os) const;
     };