xo-interpreter2: + VsmApplyClosureFrame [WIP, not used]

include/xo/interpreter2/DVsmApplyClosureFrame.hpp

@@ -0,0 +1,52 @@
+/** @file DVsmApplyClosureFrame.hpp
+ *
+ *  @author Roland Conybeare, Feb 2026
+ **/
+
+#pragma once
+
+#include "VsmInstr.hpp"
+#include "DLocalEnv.hpp"
+#include <xo/expression2/DApplyExpr.hpp>
+
+namespace xo {
+    namespace scm {
+
+        /** Frame to preserve VSM registers:
+         *   (stack_, parent_, cont_)
+         *  while applying a closure.
+         **/
+        class DVsmApplyClosureFrame {
+        public:
+            using ACollector = xo::mm::ACollector;
+            using AAllocator = xo::mm::AAllocator;
+            using AGCObject = xo::mm::AGCObject;
+            using ppindentinfo = xo::print::ppindentinfo;
+
+        public:
+            DVsmApplyClosureFrame(obj<AGCObject> stack,
+                                  VsmInstr cont,
+                                  DLocalEnv * env);
+
+            /** gcobject facet **/
+            std::size_t shallow_size() const noexcept;
+            DVsmApplyClosureFrame * shallow_copy(obj<AAllocator> mm) const noexcept;
+            std::size_t forward_children(obj<ACollector> gc) noexcept;
+
+            /** pretty-printing support **/
+            bool pretty(const ppindentinfo & ppii) const;
+
+        protected:
+            /** saved VSM stack_ register **/
+            obj<AGCObject> stack_;
+            /** saved VSM cont_ register **/
+            VsmInstr cont_;
+            /** saved VSM local_env_ register **/
+            DLocalEnv * local_env_ = nullptr;
+        };
+
+
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end DVsmApplyClosureFrame.hpp */