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

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

xo-expression/src/expression/LocalEnv.cpp

@@ -0,0 +1,44 @@
+/* file LocalEnv.cpp
+ *
+ * author: Roland Conybeare
+ */
+
+#include "LocalEnv.hpp"
+
+namespace xo {
+    namespace ast {
+        binding_path
+        LocalEnv::lookup_local_binding(const std::string & vname) const
+        {
+            int j_slot = 0;
+            for (const auto & arg : argv_) {
+                if (arg->name() == vname)
+                    return { 0 /*i_link*/, j_slot };
+                ++j_slot;
+            }
+
+            return { -2 /*i_link: sentinel*/, 0 };
+        } /*lookup_local_binding*/
+
+        binding_path
+        LocalEnv::lookup_binding(const std::string & vname) const
+        {
+            {
+                auto local = this->lookup_local_binding(vname);
+
+                if (local.i_link_ == 0)
+                    return local;
+            }
+
+            auto free = parent_env_->lookup_binding(vname);
+
+            if (free.i_link_ == -1)
+                return free;
+            else
+                return { free.i_link_ + 1, free.j_slot_ };
+        } /*lookup_binding*/
+    } /*namespace ast*/
+} /*namespace xo*/
+
+
+/* end LocalEnv.cpp */