xo-expression: + Variable + apply/lambda fixes

src/expression/CMakeLists.txt

@@ -5,6 +5,7 @@ set(SELF_SRCS
     Expression.cpp
     Apply.cpp
     Lambda.cpp
+    Variable.cpp
     #init_reflect.cpp
 )
 

src/expression/Lambda.cpp

@@ -8,6 +8,7 @@ namespace xo {
         void
         Lambda::display(std::ostream & os) const {
             os << "<Lambda"
+               << xtag("name", name_)
                << xtag("argv", argv_)
                << xtag("body", body_)
                << ">";

src/expression/Variable.cpp

@@ -0,0 +1,17 @@
+/* @file Variable.cpp */
+
+#include "Variable.hpp"
+
+namespace xo {
+    namespace ast {
+        void
+        Variable::display(std::ostream & os) const {
+            os << "<Variable"
+               << xtag("name", name_)
+               << ">";
+        } /*display*/
+    } /*namespace ast*/
+} /*namespace xo*/
+
+
+/* end Variable.cpp */