xo-interpreter: Object->TaggedPtr conversion (prep for primitives)

include/xo/expression/ProcedureExprInterface.hpp

@@ -0,0 +1,33 @@
+/** @file FunctionExprInterface.hpp
+ *
+ *  Author: Roland Conybeare
+ **/
+
+#pragma once
+
+#include "Expression.hpp"
+//#include <cstdint>
+
+namespace xo {
+    namespace scm {
+        class ProcedureExprInterface : public Expression {
+        public:
+            ProcedureExprInterface(exprtype extype, TypeDescr fn_type)
+                : Expression(extype, fn_type) {}
+
+            /** downcast from Expression **/
+            static bp<ProcedureExprInterface> from(bp<Expression> x) {
+                return bp<ProcedureExprInterface>::from(x);
+            }
+
+            virtual const std::string & name() const = 0;
+            virtual int n_arg() const = 0; // { return this->value_td()->n_fn_arg(); }
+            virtual TypeDescr fn_retval() const = 0; // { return this->value_td()->fn_retval(); }
+            virtual TypeDescr fn_arg(uint32_t i) const = 0; // { return this->value_td()->fn_arg(i); }
+
+        private:
+        }; /*FunctionInterface*/
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/** end FunctionExprInterface.hpp **/