xo-expression: + binding_path + assoc w/ each Variable

src/expression/Variable.cpp

@@ -1,9 +1,16 @@
 /* @file Variable.cpp */
 
 #include "Variable.hpp"
+#include "Environment.hpp"
 
 namespace xo {
     namespace ast {
+        void
+        Variable::attach_envs(ref::brw<Environment> e) {
+            /** e makes accessible all enclosing lexical scopes **/
+            this->path_ = e->lookup_binding(this->name_);
+        } /*attach_envs*/
+
         void
         Variable::display(std::ostream & os) const {
             os << "<Variable"