Add 'xo-expression/' from commit '5ac3c03a0c'

git-subtree-dir: xo-expression
git-subtree-mainline: d0f5ccc1ce
git-subtree-split: 5ac3c03a0c

xo-expression/src/expression/GeneralizedExpression.cpp

@@ -0,0 +1,14 @@
+/* @file GeneralizedExpression.cpp */
+
+#include "GeneralizedExpression.hpp"
+
+namespace xo {
+    namespace ast {
+        std::string
+        GeneralizedExpression::display_string() const {
+            return tostr(*this);
+        }
+    } /*namespace ast*/
+} /*namespace xo*/
+
+/* end GeneralizedExpression.cpp */