xo-expression: + Variable + apply/lambda fixes

include/xo/expression/Variable.hpp

@@ -0,0 +1,42 @@
+/** @file Variable.hpp
+ *
+ *  Author: Roland Conybeare
+ **/
+
+#pragma once
+
+#include "Expression.hpp"
+
+namespace xo {
+    namespace ast {
+
+        /** @class Variable
+         *  @brief syntax for a variable reference
+         **/
+        class Variable : public Expression {
+        public:
+            Variable(const std::string & name) : Expression(exprtype::variable), name_{name} {}
+
+            /** downcast from Expression **/
+            static ref::brw<Variable> from(ref::brw<Expression> x) {
+                return ref::brw<Variable>::from(x);
+            }
+
+            const std::string & name() const { return name_; }
+
+            virtual void display(std::ostream & os) const;
+
+        private:
+            /** variable name **/
+            std::string name_;
+        }; /*Variable*/
+
+        inline ref::rp<Variable>
+        make_var(const std::string & name) {
+            return new Variable(name);
+        }
+    } /*namespace ast*/
+} /*namespace xo*/
+
+
+/** end Variable.hpp **/