Added a "null" value for value expressions

src/report.cc

@@ -305,6 +305,10 @@ value_t report_t::fn_ansify_if(call_scope_t& scope)
 }
 
 namespace {
+  value_t fn_null(call_scope_t&) {
+    return NULL_VALUE;
+  }
+
   template <class Type        = post_t,
 	    class handler_ptr = post_handler_ptr,
 	    void (report_t::*report_method)(handler_ptr) =
@@ -716,6 +720,11 @@ expr_t::ptr_op_t report_t::lookup(const string& name)
       return MAKE_FUNCTOR(report_t::fn_market);
     break;
 
+  case 'n':
+    if (is_eq(p, "null"))
+      return WRAP_FUNCTOR(fn_null);
+    break;
+
   case 'o':
     if (WANT_OPT()) { const char * q = p + OPT_PREFIX_LEN;
       if (option_t<report_t> * handler = lookup_option(q))

src/value.cc

@@ -1515,7 +1515,7 @@ void value_t::dump(std::ostream& out, const bool relaxed) const
 {
   switch (type()) {
   case VOID:
-    out << "<null>";
+    out << "null";
     break;
 
   case BOOLEAN: