xo-reader2 stack: top-level lambda w/ apply parses

CMakeLists.txt

@@ -146,6 +146,44 @@ xo_add_genfacetimpl(
 
 # ----------------------------------------------------------------
 
+# note: manual target; generated code committed to git
+xo_add_genfacetimpl(
+    TARGET xo-expression2-facetimpl-expression-varref
+    FACET_PKG xo_expression2
+    FACET Expression
+    REPR VarRef
+    INPUT idl/IExpression_DVarRef.json5
+    OUTPUT_HPP_DIR include/xo/expression2
+    OUTPUT_IMPL_SUBDIR detail
+    OUTPUT_CPP_DIR src/expression2
+)
+
+# note: manual target; generated code committed to git
+xo_add_genfacetimpl(
+    TARGET xo-expression2-facetimpl-gcobject-varref
+    FACET_PKG xo_gc
+    FACET GCObject
+    REPR VarRef
+    INPUT idl/IGCObject_DVarRef.json5
+    OUTPUT_HPP_DIR include/xo/expression2
+    OUTPUT_IMPL_SUBDIR detail
+    OUTPUT_CPP_DIR src/expression2
+)
+
+# note: manual target; generated code committed to git
+xo_add_genfacetimpl(
+    TARGET xo-expression2-facetimpl-printable-varref
+    FACET_PKG xo_printable2
+    FACET Printable
+    REPR VarRef
+    INPUT idl/IPrintable_DVarRef.json5
+    OUTPUT_HPP_DIR include/xo/expression2
+    OUTPUT_IMPL_SUBDIR detail
+    OUTPUT_CPP_DIR src/expression2
+)
+
+# ----------------------------------------------------------------
+
 # note: manual target; generated code committed to git
 xo_add_genfacetimpl(
     TARGET xo-expression2-facetimpl-expression-defineexpr
@@ -184,6 +222,18 @@ xo_add_genfacetimpl(
     OUTPUT_CPP_DIR src/expression2
 )
 
+# note: manual target; generated code committed to git
+xo_add_genfacetimpl(
+    TARGET xo-expression2-facetimpl-gcobject-applyexpr
+    FACET_PKG xo_gc
+    FACET GCObject
+    REPR ApplyExpr
+    INPUT idl/IGCObject_DApplyExpr.json5
+    OUTPUT_HPP_DIR include/xo/expression2
+    OUTPUT_IMPL_SUBDIR detail
+    OUTPUT_CPP_DIR src/expression2
+)
+
 # note: manual target; generated code committed to git
 xo_add_genfacetimpl(
     TARGET xo-expression2-facetimpl-printable-applyexpr

idl/Expression.json5

@@ -67,4 +67,5 @@
             attributes: [],
         }
     ],
+    router_facet_explicit_content: [ ],
 }

idl/IExpression_DVarRef.json5

@@ -0,0 +1,12 @@
+{
+    mode: "implementation",
+    includes: [ "\"Expression.hpp\"" ],
+    local_types: [ ],
+    namespace1: "xo",
+    namespace2: "scm",
+    facet_idl: "idl/Expression.json5",
+    brief: "provide AExpression interface for DVarRef state",
+    using_doxygen: true,
+    repr: "DVarRef",
+    doc: ["doc for IExpression+DVarRef" ],
+}

idl/IGCObject_DApplyExpr.json5

@@ -0,0 +1,15 @@
+{
+    mode: "implementation",
+    includes: [
+        "<xo/gc/GCObject.hpp>",
+        "<xo/alloc2/Allocator.hpp>"
+    ],
+    local_types: [ ],
+    namespace1: "xo",
+    namespace2: "scm",
+    facet_idl: "idl/GCObject.json5",
+    brief: "provide AGCObject interface for DApplyExpr",
+    using_doxygen: true,
+    repr: "DApplyExpr",
+    doc: [ "implement AGCObject for DApplyExpr" ],
+}

idl/IGCObject_DVarRef.json5

@@ -0,0 +1,15 @@
+{
+    mode: "implementation",
+    includes: [
+        "<xo/gc/GCObject.hpp>",
+        "<xo/alloc2/Allocator.hpp>"
+    ],
+    local_types: [ ],
+    namespace1: "xo",
+    namespace2: "scm",
+    facet_idl: "idl/GCObject.json5",
+    brief: "provide AGCObject interface for DVarRef",
+    using_doxygen: true,
+    repr: "DVarRef",
+    doc: [ "implement AGCObject for DVarRef" ],
+}

idl/IPrintable_DVarRef.json5

@@ -0,0 +1,13 @@
+{
+    mode: "implementation",
+    includes: [ "<xo/printable2/Printable.hpp>",
+                "<xo/printable2/detail/IPrintable_Xfer.hpp>" ],
+    local_types: [ ],
+    namespace1: "xo",
+    namespace2: "scm",
+    facet_idl: "idl/Printable.json5",
+    brief: "provide APrintable interface for DVarRef",
+    using_doxygen: true,
+    repr: "DVarRef",
+    doc: [ "implement APrintable for DVarRef" ],
+}

include/xo/expression2/ApplyExpr.hpp

@@ -7,7 +7,7 @@
 
 #include "DApplyExpr.hpp"
 #include "detail/IExpression_DApplyExpr.hpp"
-//#include "detail/IGCObject_DApplyExpr.hpp"
+#include "detail/IGCObject_DApplyExpr.hpp"
 #include "detail/IPrintable_DApplyExpr.hpp"
 
 /* end ApplyExpr.hpp */

include/xo/expression2/Binding.hpp

@@ -5,14 +5,15 @@
 
 #pragma once
 
+#include <iostream>
 #include <cstdint>
 
 namespace xo {
     namespace scm {
         class Binding {
         public:
-            static constexpr int32_t s_link_sentinel = -2;
-            static constexpr int32_t s_link_global = -1;
+            static constexpr int32_t c_link_sentinel = -2;
+            static constexpr int32_t c_link_global = -1;
 
         public:
             Binding() : i_link_{-2}, j_slot_{-1} {}
@@ -21,18 +22,22 @@ namespace xo {
 
             static Binding null() { return Binding(); }
             /** global bindings are located by symbol name **/
-            static Binding global() { return Binding(s_link_global, 0); }
+            static Binding global() { return Binding(c_link_global, 0); }
             static Binding local(int32_t j_slot) { return Binding(0, j_slot); }
+            static Binding relative(int32_t i_link, Binding def);
 
             bool is_null() const {
-                return (i_link_ == s_link_sentinel) && (j_slot_ == -1);
+                return (i_link_ == c_link_sentinel) && (j_slot_ == -1);
             }
-            bool is_global() const { return i_link_ == s_link_global; }
+            bool is_global() const { return i_link_ == c_link_global; }
             bool is_local() const { return (i_link_ == 0) && (j_slot_ >= 0); }
 
             int32_t i_link() const noexcept { return i_link_; }
             int32_t j_slot() const noexcept { return j_slot_; }
 
+            /** print human-readable repr to stream @p os **/
+            void print(std::ostream & os) const;
+
         private:
             /**
              *  >= 0: number of parent links to traverse
@@ -40,13 +45,18 @@ namespace xo {
              *    -1: resolve globally
              *    -2: sentinel (binding info not computed)
              **/
-            int32_t i_link_ = s_link_sentinel;
+            int32_t i_link_ = c_link_sentinel;
             /** if @ref i_link_ >= 0, frame offset
              *  (in 'variables' not bytes).
              *  ignored if @ref i_link_ is global
              **/
             int32_t j_slot_ = -1;
         };
+
+        inline std::ostream & operator<< (std::ostream & os, Binding x) {
+            x.print(os);
+            return os;
+        }
     } /*namespace scm*/
 } /*namespace xo*/
 

include/xo/expression2/DApplyExpr.hpp

@@ -20,6 +20,7 @@ namespace xo {
          **/
         class DApplyExpr {
         public:
+            using ACollector = xo::mm::ACollector;
             using AAllocator = xo::mm::AAllocator;
             using TypeDescr = xo::reflect::TypeDescr;
             using ppindentinfo = xo::print::ppindentinfo;
@@ -81,7 +82,9 @@ namespace xo {
             /** @defgroup scm-applyexpr-gcobject-facet **/
             ///@{
 
-            // shallow_copy() etc.
+            std::size_t shallow_size() const noexcept;
+            DApplyExpr * shallow_copy(obj<AAllocator> mm) const noexcept;
+            std::size_t forward_children(obj<ACollector> gc) noexcept;
 
             ///@}
             /** @defgroup scm-applyexpr-printable-facet **/

include/xo/expression2/DLocalSymtab.hpp

@@ -31,14 +31,14 @@ namespace xo {
 
             struct Slot {
                 Slot() = default;
-                explicit Slot(const DVariable * var) : var_{var} {}
+                explicit Slot(DVariable * var) : var_{var} {}
 
                 /** variable representing a formal argument.
                  *  binding will be correct only within the same layer
                  *  as top-level lambda body
                  *  (i.e. up to the doorstep of each and every nested lambda)
                  **/
-                const DVariable * var_ = nullptr;
+                DVariable * var_ = nullptr;
             };
 
         public:
@@ -65,7 +65,7 @@ namespace xo {
             size_type capacity() const noexcept { return capacity_; }
             size_type size() const noexcept { return size_; }
 
-            const DVariable * lookup_var(Binding ix) const noexcept {
+             DVariable * lookup_var(Binding ix) noexcept {
                 assert(ix.i_link() == 0);
                 assert(ix.j_slot() < static_cast<int32_t>(size_));
 

include/xo/expression2/DVarRef.hpp

@@ -0,0 +1,84 @@
+/** @file DVarRef.hpp
+ *
+ *  @author Roland Conybeare, Feb 2026
+ **/
+
+#pragma once
+
+#include "Variable.hpp"
+
+namespace xo {
+    namespace scm {
+
+        /** @class DVarRef
+         *  @brief syntax for a variable reference
+         *
+         *  Reference to a known variable possibly
+         *  defined in another scope.
+         *  For non-local non-global variables,
+         **/
+        class DVarRef {
+        public:
+            using ppindentinfo = xo::print::ppindentinfo;
+            using ACollector = xo::mm::ACollector;
+            using AAllocator = xo::mm::AAllocator;
+            using TypeDescr = xo::reflect::TypeDescr;
+
+        public:
+            DVarRef(DVariable * vardef,
+                    Binding path);
+
+            /** create instance
+             *  @p mm      memory allocator
+             *  @p vardef  variable definition (name, typeref, binding)
+             *  @p link    number of lexical scope boundaries we must cross
+             *             to reach scope containing @p vardef.
+             *             Only relevant for non-global vardef
+             **/
+            static DVarRef * make(obj<AAllocator> mm,
+                                  DVariable * vardef,
+                                  int32_t link);
+
+            const DUniqueString * name() const;
+            Binding path() const { return path_; }
+
+            /** @defgroup scm-variable-expression-facet **/
+            ///@{
+
+            exprtype extype() const noexcept { return exprtype::varref; }
+            TypeRef typeref() const noexcept;
+            TypeDescr valuetype() const noexcept;
+            void assign_valuetype(TypeDescr td) noexcept;
+
+            ///@}
+            /** @defgroup scm-variable-gcobject-facet **/
+            ///@{
+
+            size_t shallow_size() const noexcept;
+            DVarRef * shallow_copy(obj<AAllocator> mm) const noexcept;
+            size_t forward_children(obj<ACollector> gc) noexcept;
+
+            ///@}
+            /** @defgroup scm-variable-printable-facet **/
+            ///@{
+
+            bool pretty(const ppindentinfo & ppii) const;
+
+            ///@}
+
+        private:
+            /** variable definition. Created in the sccope where variable introduced.
+             *  Has an associated @ref Binding, but that binding is only correct
+             *  around any nested scopes.
+             **/
+            DVariable * vardef_ = nullptr;
+
+            /** at runtime: navigate environemnt via this path to get
+             *  runtime memory location for this variable
+             **/
+            Binding path_;
+        };
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end DVarRef.hpp */

include/xo/expression2/VarRef.hpp

@@ -0,0 +1,13 @@
+/** @file VarRef.hpp
+ *
+ *  @author Roland Conybeare, Feb 2026
+ **/
+
+#pragma once
+
+#include "DVarRef.hpp"
+#include "detail/IExpression_DVarRef.hpp"
+#include "detail/IGCObject_DVarRef.hpp"
+#include "detail/IPrintable_DVarRef.hpp"
+
+/* end VarRef.hpp */

include/xo/expression2/detail/IExpression_DVarRef.hpp

@@ -0,0 +1,66 @@
+/** @file IExpression_DVarRef.hpp
+ *
+ *  Generated automagically from ingredients:
+ *  1. code generator:
+ *       [xo-facet/codegen/genfacet]
+ *     arguments:
+ *       --input [idl/IExpression_DVarRef.json5]
+ *  2. jinja2 template for abstract facet .hpp file:
+ *       [iface_facet_repr.hpp.j2]
+ *  3. idl for facet methods
+ *       [idl/IExpression_DVarRef.json5]
+ **/
+
+#pragma once
+
+#include "Expression.hpp"
+#include "Expression.hpp"
+#include "DVarRef.hpp"
+
+namespace xo { namespace scm { class IExpression_DVarRef; } }
+
+namespace xo {
+    namespace facet {
+        template <>
+        struct FacetImplementation<xo::scm::AExpression,
+                                   xo::scm::DVarRef>
+        {
+            using ImplType = xo::scm::IExpression_Xfer
+              <xo::scm::DVarRef,
+               xo::scm::IExpression_DVarRef>;
+        };
+    }
+}
+
+namespace xo {
+    namespace scm {
+        /** @class IExpression_DVarRef
+         **/
+        class IExpression_DVarRef {
+        public:
+            /** @defgroup scm-expression-dvarref-type-traits **/
+            ///@{
+            using TypeDescr = xo::scm::AExpression::TypeDescr;
+            using Copaque = xo::scm::AExpression::Copaque;
+            using Opaque = xo::scm::AExpression::Opaque;
+            ///@}
+            /** @defgroup scm-expression-dvarref-methods **/
+            ///@{
+            // const methods
+            /** expression type (constant | apply | ..) **/
+            static exprtype extype(const DVarRef & self) noexcept;
+            /** placeholder for type giving possible values for this expression **/
+            static TypeRef typeref(const DVarRef & self) noexcept;
+            /** type giving possible values for this expression. Maybe null before typecheck **/
+            static TypeDescr valuetype(const DVarRef & self) noexcept;
+
+            // non-const methods
+            /** assing to valuetype member. Useful when scaffolding expressions **/
+            static void assign_valuetype(DVarRef & self, TypeDescr td) noexcept;
+            ///@}
+        };
+
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end */

include/xo/expression2/detail/IGCObject_DApplyExpr.hpp

@@ -0,0 +1,67 @@
+/** @file IGCObject_DApplyExpr.hpp
+ *
+ *  Generated automagically from ingredients:
+ *  1. code generator:
+ *       [xo-facet/codegen/genfacet]
+ *     arguments:
+ *       --input [idl/IGCObject_DApplyExpr.json5]
+ *  2. jinja2 template for abstract facet .hpp file:
+ *       [iface_facet_repr.hpp.j2]
+ *  3. idl for facet methods
+ *       [idl/IGCObject_DApplyExpr.json5]
+ **/
+
+#pragma once
+
+#include "GCObject.hpp"
+#include <xo/gc/GCObject.hpp>
+#include <xo/alloc2/Allocator.hpp>
+#include "DApplyExpr.hpp"
+
+namespace xo { namespace scm { class IGCObject_DApplyExpr; } }
+
+namespace xo {
+    namespace facet {
+        template <>
+        struct FacetImplementation<xo::mm::AGCObject,
+                                   xo::scm::DApplyExpr>
+        {
+            using ImplType = xo::mm::IGCObject_Xfer
+              <xo::scm::DApplyExpr,
+               xo::scm::IGCObject_DApplyExpr>;
+        };
+    }
+}
+
+namespace xo {
+    namespace scm {
+        /** @class IGCObject_DApplyExpr
+         **/
+        class IGCObject_DApplyExpr {
+        public:
+            /** @defgroup scm-gcobject-dapplyexpr-type-traits **/
+            ///@{
+            using size_type = xo::mm::AGCObject::size_type;
+            using AAllocator = xo::mm::AGCObject::AAllocator;
+            using ACollector = xo::mm::AGCObject::ACollector;
+            using Copaque = xo::mm::AGCObject::Copaque;
+            using Opaque = xo::mm::AGCObject::Opaque;
+            ///@}
+            /** @defgroup scm-gcobject-dapplyexpr-methods **/
+            ///@{
+            // const methods
+            /** memory consumption for this instance **/
+            static size_type shallow_size(const DApplyExpr & self) noexcept;
+            /** copy instance using allocator **/
+            static Opaque shallow_copy(const DApplyExpr & self, obj<AAllocator> mm) noexcept;
+
+            // non-const methods
+            /** during GC: forward immdiate children **/
+            static size_type forward_children(DApplyExpr & self, obj<ACollector> gc) noexcept;
+            ///@}
+        };
+
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end */

include/xo/expression2/detail/IGCObject_DVarRef.hpp

@@ -0,0 +1,67 @@
+/** @file IGCObject_DVarRef.hpp
+ *
+ *  Generated automagically from ingredients:
+ *  1. code generator:
+ *       [xo-facet/codegen/genfacet]
+ *     arguments:
+ *       --input [idl/IGCObject_DVarRef.json5]
+ *  2. jinja2 template for abstract facet .hpp file:
+ *       [iface_facet_repr.hpp.j2]
+ *  3. idl for facet methods
+ *       [idl/IGCObject_DVarRef.json5]
+ **/
+
+#pragma once
+
+#include "GCObject.hpp"
+#include <xo/gc/GCObject.hpp>
+#include <xo/alloc2/Allocator.hpp>
+#include "DVarRef.hpp"
+
+namespace xo { namespace scm { class IGCObject_DVarRef; } }
+
+namespace xo {
+    namespace facet {
+        template <>
+        struct FacetImplementation<xo::mm::AGCObject,
+                                   xo::scm::DVarRef>
+        {
+            using ImplType = xo::mm::IGCObject_Xfer
+              <xo::scm::DVarRef,
+               xo::scm::IGCObject_DVarRef>;
+        };
+    }
+}
+
+namespace xo {
+    namespace scm {
+        /** @class IGCObject_DVarRef
+         **/
+        class IGCObject_DVarRef {
+        public:
+            /** @defgroup scm-gcobject-dvarref-type-traits **/
+            ///@{
+            using size_type = xo::mm::AGCObject::size_type;
+            using AAllocator = xo::mm::AGCObject::AAllocator;
+            using ACollector = xo::mm::AGCObject::ACollector;
+            using Copaque = xo::mm::AGCObject::Copaque;
+            using Opaque = xo::mm::AGCObject::Opaque;
+            ///@}
+            /** @defgroup scm-gcobject-dvarref-methods **/
+            ///@{
+            // const methods
+            /** memory consumption for this instance **/
+            static size_type shallow_size(const DVarRef & self) noexcept;
+            /** copy instance using allocator **/
+            static Opaque shallow_copy(const DVarRef & self, obj<AAllocator> mm) noexcept;
+
+            // non-const methods
+            /** during GC: forward immdiate children **/
+            static size_type forward_children(DVarRef & self, obj<ACollector> gc) noexcept;
+            ///@}
+        };
+
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end */

include/xo/expression2/detail/IPrintable_DVarRef.hpp

@@ -0,0 +1,62 @@
+/** @file IPrintable_DVarRef.hpp
+ *
+ *  Generated automagically from ingredients:
+ *  1. code generator:
+ *       [xo-facet/codegen/genfacet]
+ *     arguments:
+ *       --input [idl/IPrintable_DVarRef.json5]
+ *  2. jinja2 template for abstract facet .hpp file:
+ *       [iface_facet_repr.hpp.j2]
+ *  3. idl for facet methods
+ *       [idl/IPrintable_DVarRef.json5]
+ **/
+
+#pragma once
+
+#include "Printable.hpp"
+#include <xo/printable2/Printable.hpp>
+#include <xo/printable2/detail/IPrintable_Xfer.hpp>
+#include "DVarRef.hpp"
+
+namespace xo { namespace scm { class IPrintable_DVarRef; } }
+
+namespace xo {
+    namespace facet {
+        template <>
+        struct FacetImplementation<xo::print::APrintable,
+                                   xo::scm::DVarRef>
+        {
+            using ImplType = xo::print::IPrintable_Xfer
+              <xo::scm::DVarRef,
+               xo::scm::IPrintable_DVarRef>;
+        };
+    }
+}
+
+namespace xo {
+    namespace scm {
+        /** @class IPrintable_DVarRef
+         **/
+        class IPrintable_DVarRef {
+        public:
+            /** @defgroup scm-printable-dvarref-type-traits **/
+            ///@{
+            using ppindentinfo = xo::print::APrintable::ppindentinfo;
+            using Copaque = xo::print::APrintable::Copaque;
+            using Opaque = xo::print::APrintable::Opaque;
+            ///@}
+            /** @defgroup scm-printable-dvarref-methods **/
+            ///@{
+            // const methods
+            /** Pretty-printing support for this object.
+See [xo-indentlog/xo/indentlog/pretty.hpp] **/
+            static bool pretty(const DVarRef & self, const ppindentinfo & ppii);
+
+            // non-const methods
+            ///@}
+        };
+
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end */

include/xo/expression2/exprtype.hpp

@@ -36,8 +36,10 @@ namespace xo {
             /** function definition **/
             lambda,
 
-            /** variable reference **/
+            /** variable definition **/
             variable,
+            /** variabele reference (possibly non-local) **/
+            varref,
             /** if-then-else **/
             ifexpr,
             /** sequence **/
@@ -65,14 +67,16 @@ namespace xo {
             case exprtype::assign: return "assign";
 #endif
             case exprtype::apply: return "apply";
-#ifdef NOT_YET
             case exprtype::lambda: return "lambda";
             case exprtype::variable: return "variable";
+            case exprtype::varref: return "varref";
             case exprtype::ifexpr: return "if_expr";
             case exprtype::sequence: return "sequence";
+#ifdef NOT_YET
             case exprtype::convert: return "convert";
 #endif
-            default: break;
+            case exprtype::N: break;
+            //default: break;
             }
 
             return "???exprtype???";

src/expression2/Binding.cpp

@@ -0,0 +1,41 @@
+/** @file Binding.cpp
+ *
+ *  @author Roland Conybeare, Feb 2026
+ **/
+
+#include "Binding.hpp"
+#include <cassert>
+
+namespace xo {
+    namespace scm {
+
+        Binding
+        Binding::relative(int32_t i_link, Binding def)
+        {
+            if (def.i_link_ == Binding::c_link_global) {
+                // for globally defined vars, i_link always -1
+                return def;
+            } else if (def.i_link_ >= 0) {
+                return Binding(i_link + def.i_link_, def.j_slot_);
+            } else {
+                assert(false);
+                return Binding();
+            }
+        }
+
+        void
+        Binding::print(std::ostream & os) const
+        {
+            if (i_link_ == c_link_global) {
+                os << "{path:global}";
+            } else if (i_link_ == c_link_sentinel) {
+                os << "{path}";
+            } else {
+                os << "{path:" << i_link_ << ":" << j_slot_ << "}";
+            }
+        }
+
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end Binding.cpp */

src/expression2/CMakeLists.txt

@@ -3,9 +3,12 @@
 set(SELF_LIB xo_expression2)
 set(SELF_SRCS
     init_expression2.cpp
+    expression2_register_facets.cpp
+    expression2_register_types.cpp
 
     DConstant.cpp
     DVariable.cpp
+    DVarRef.cpp
     DDefineExpr.cpp
     DLambdaExpr.cpp
     DApplyExpr.cpp
@@ -13,6 +16,7 @@ set(SELF_SRCS
     DSequenceExpr.cpp
 
     TypeRef.cpp
+    Binding.cpp
 
     IExpression_Any.cpp
 
@@ -24,10 +28,15 @@ set(SELF_SRCS
     IGCObject_DVariable.cpp
     IPrintable_DVariable.cpp
 
+    IExpression_DVarRef.cpp
+    IGCObject_DVarRef.cpp
+    IPrintable_DVarRef.cpp
+
     IExpression_DDefineExpr.cpp
     IPrintable_DDefineExpr.cpp
 
     IExpression_DApplyExpr.cpp
+    IGCObject_DApplyExpr.cpp
     IPrintable_DApplyExpr.cpp
 
     IExpression_DLambdaExpr.cpp
@@ -55,8 +64,6 @@ set(SELF_SRCS
     IGCObject_DUniqueString.cpp
     IPrintable_DUniqueString.cpp
 
-    expression2_register_facets.cpp
-    expression2_register_types.cpp
     )
 
 xo_add_shared_library4(${SELF_LIB} ${PROJECT_NAME}Targets ${PROJECT_VERSION} 1 ${SELF_SRCS})

src/expression2/DApplyExpr.cpp

@@ -102,6 +102,48 @@ namespace xo {
             typeref_.resolve(td);
         }
 
+        // ----- gcobject facet -----
+
+        std::size_t
+        DApplyExpr::shallow_size() const noexcept {
+            return sizeof(DApplyExpr) + (n_args_ * sizeof(obj<AExpression>));
+        }
+
+        DApplyExpr *
+        DApplyExpr::shallow_copy(obj<AAllocator> mm) const noexcept {
+            DApplyExpr * copy = (DApplyExpr *)mm.alloc_copy((std::byte *)this);
+
+            if (copy) {
+                copy->typeref_ = typeref_;
+                copy->fn_ = fn_;
+                copy->n_args_ = n_args_;
+
+                constexpr auto c_obj_z = sizeof(obj<AExpression>);
+
+                ::memcpy((void*)&(copy->args_[0]), (void*)&(args_[0]), n_args_ * c_obj_z);
+            }
+
+            return copy;
+        }
+
+        std::size_t
+        DApplyExpr::forward_children(obj<ACollector> gc) noexcept
+        {
+            for (size_type i = 0; i < n_args_; ++i) {
+                obj<AExpression> & arg = args_[i];
+
+                // runtime poly here
+                obj<AGCObject> arg_gco = arg.to_facet<AGCObject>();
+
+                // need the data address within *this
+                gc.forward_inplace(arg_gco.iface(), (void **)(&arg.data_));
+            }
+
+            return shallow_size();
+        }
+
+        // ----- printable facet -----
+
         bool
         DApplyExpr::pretty(const ppindentinfo & ppii) const {
             using xo::print::ppstate;

src/expression2/DVarRef.cpp

@@ -0,0 +1,105 @@
+/** @file DVarRef.cpp
+ *
+ *  @author Roland Conybeare, Feb 2026
+ **/
+
+#include "DVarRef.hpp"
+
+namespace xo {
+    using xo::mm::AGCObject;
+    using xo::reflect::TypeDescr;
+
+    namespace scm {
+
+        DVarRef::DVarRef(DVariable * vardef,
+                         Binding path)
+                : vardef_{vardef},
+                  path_{path}
+        {}
+
+        DVarRef *
+        DVarRef::make(obj<AAllocator> mm,
+                      DVariable * vardef,
+                      int32_t link)
+        {
+            assert(vardef);
+
+            void * mem = mm.alloc_for<DVarRef>();
+
+            return new (mem) DVarRef(vardef,
+                                     Binding::relative(link,
+                                                       vardef->path()));
+        }
+
+        const DUniqueString *
+        DVarRef::name() const {
+            return vardef_->name();
+        }
+
+        TypeRef
+        DVarRef::typeref() const noexcept {
+            assert(vardef_);
+
+            return vardef_->typeref();
+        }
+
+        TypeDescr
+        DVarRef::valuetype() const noexcept
+        {
+            return this->typeref().td();
+        }
+
+        void
+        DVarRef::assign_valuetype(TypeDescr td) noexcept
+        {
+            assert(vardef_);
+            vardef_->assign_valuetype(td);
+        }
+
+        // gcobject facet
+
+        std::size_t
+        DVarRef::shallow_size() const noexcept
+        {
+            return sizeof(DVarRef);
+        }
+
+        DVarRef *
+        DVarRef::shallow_copy(obj<AAllocator> mm) const noexcept
+        {
+            DVarRef * copy = (DVarRef *)mm.alloc_copy((std::byte *)this);
+
+            if (copy)
+                *copy = *this;
+
+            return copy;
+        }
+
+        std::size_t
+        DVarRef::forward_children(obj<ACollector> gc) noexcept
+        {
+            // TODO: this can be helper in RCollector interface
+            auto iface = xo::facet::impl_for<AGCObject,DVariable>();
+            gc.forward_inplace(&iface, (void **)vardef_);
+
+            // TODO: concept to indicate that no gc pointers in Binding
+
+            return shallow_size();
+        }
+
+        // printable facet
+
+        bool
+        DVarRef::pretty(const ppindentinfo & ppii) const
+        {
+            return ppii.pps()->pretty_struct
+                       (ppii,
+                        "DVarRef",
+                        refrtag("name", std::string_view(*(this->name()))),
+                        refrtag("path", this->path_));
+        }
+
+    }
+} /*namespace xo*/
+
+/* end DVarRef.cpp */

src/expression2/IExpression_DVarRef.cpp

@@ -0,0 +1,45 @@
+/** @file IExpression_DVarRef.cpp
+ *
+ *  Generated automagically from ingredients:
+ *  1. code generator:
+ *       [xo-facet/codegen/genfacet]
+ *     arguments:
+ *       --input [idl/IExpression_DVarRef.json5]
+ *  2. jinja2 template for abstract facet .hpp file:
+ *       [iface_facet_any.hpp.j2]
+ *  3. idl for facet methods
+ *       [idl/IExpression_DVarRef.json5]
+**/
+
+#include "detail/IExpression_DVarRef.hpp"
+
+namespace xo {
+    namespace scm {
+        auto
+        IExpression_DVarRef::extype(const DVarRef & self) noexcept -> exprtype
+        {
+            return self.extype();
+        }
+
+        auto
+        IExpression_DVarRef::typeref(const DVarRef & self) noexcept -> TypeRef
+        {
+            return self.typeref();
+        }
+
+        auto
+        IExpression_DVarRef::valuetype(const DVarRef & self) noexcept -> TypeDescr
+        {
+            return self.valuetype();
+        }
+
+        auto
+        IExpression_DVarRef::assign_valuetype(DVarRef & self, TypeDescr td) noexcept -> void
+        {
+            self.assign_valuetype(td);
+        }
+
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end IExpression_DVarRef.cpp */

src/expression2/IGCObject_DApplyExpr.cpp

@@ -0,0 +1,39 @@
+/** @file IGCObject_DApplyExpr.cpp
+ *
+ *  Generated automagically from ingredients:
+ *  1. code generator:
+ *       [xo-facet/codegen/genfacet]
+ *     arguments:
+ *       --input [idl/IGCObject_DApplyExpr.json5]
+ *  2. jinja2 template for abstract facet .hpp file:
+ *       [iface_facet_any.hpp.j2]
+ *  3. idl for facet methods
+ *       [idl/IGCObject_DApplyExpr.json5]
+**/
+
+#include "detail/IGCObject_DApplyExpr.hpp"
+
+namespace xo {
+    namespace scm {
+        auto
+        IGCObject_DApplyExpr::shallow_size(const DApplyExpr & self) noexcept -> size_type
+        {
+            return self.shallow_size();
+        }
+
+        auto
+        IGCObject_DApplyExpr::shallow_copy(const DApplyExpr & self, obj<AAllocator> mm) noexcept -> Opaque
+        {
+            return self.shallow_copy(mm);
+        }
+
+        auto
+        IGCObject_DApplyExpr::forward_children(DApplyExpr & self, obj<ACollector> gc) noexcept -> size_type
+        {
+            return self.forward_children(gc);
+        }
+
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end IGCObject_DApplyExpr.cpp */

src/expression2/IGCObject_DVarRef.cpp

@@ -0,0 +1,39 @@
+/** @file IGCObject_DVarRef.cpp
+ *
+ *  Generated automagically from ingredients:
+ *  1. code generator:
+ *       [xo-facet/codegen/genfacet]
+ *     arguments:
+ *       --input [idl/IGCObject_DVarRef.json5]
+ *  2. jinja2 template for abstract facet .hpp file:
+ *       [iface_facet_any.hpp.j2]
+ *  3. idl for facet methods
+ *       [idl/IGCObject_DVarRef.json5]
+**/
+
+#include "detail/IGCObject_DVarRef.hpp"
+
+namespace xo {
+    namespace scm {
+        auto
+        IGCObject_DVarRef::shallow_size(const DVarRef & self) noexcept -> size_type
+        {
+            return self.shallow_size();
+        }
+
+        auto
+        IGCObject_DVarRef::shallow_copy(const DVarRef & self, obj<AAllocator> mm) noexcept -> Opaque
+        {
+            return self.shallow_copy(mm);
+        }
+
+        auto
+        IGCObject_DVarRef::forward_children(DVarRef & self, obj<ACollector> gc) noexcept -> size_type
+        {
+            return self.forward_children(gc);
+        }
+
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end IGCObject_DVarRef.cpp */

src/expression2/IPrintable_DVarRef.cpp

@@ -0,0 +1,28 @@
+/** @file IPrintable_DVarRef.cpp
+ *
+ *  Generated automagically from ingredients:
+ *  1. code generator:
+ *       [xo-facet/codegen/genfacet]
+ *     arguments:
+ *       --input [idl/IPrintable_DVarRef.json5]
+ *  2. jinja2 template for abstract facet .hpp file:
+ *       [iface_facet_any.hpp.j2]
+ *  3. idl for facet methods
+ *       [idl/IPrintable_DVarRef.json5]
+**/
+
+#include "detail/IPrintable_DVarRef.hpp"
+
+namespace xo {
+    namespace scm {
+        auto
+        IPrintable_DVarRef::pretty(const DVarRef & self, const ppindentinfo & ppii) -> bool
+        {
+            return self.pretty(ppii);
+        }
+
+
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end IPrintable_DVarRef.cpp */

src/expression2/expression2_register_facets.cpp

@@ -16,13 +16,13 @@
 #include <xo/expression2/detail/IGCObject_DVariable.hpp>
 #include <xo/expression2/detail/IPrintable_DVariable.hpp>
 
+#include <xo/expression2/VarRef.hpp>
+
 #include <xo/expression2/detail/IExpression_DConstant.hpp>
 #include <xo/expression2/detail/IGCObject_DConstant.hpp>
 #include <xo/expression2/detail/IPrintable_DConstant.hpp>
 
-#include <xo/expression2/detail/IExpression_DApplyExpr.hpp>
-//#include <xo/expression2/detail/IGCObject_DApplyExpr.hpp>
-#include <xo/expression2/detail/IPrintable_DApplyExpr.hpp>
+#include <xo/expression2/ApplyExpr.hpp>
 
 #include <xo/expression2/detail/IExpression_DLambdaExpr.hpp>
 //#include <xo/expression2/detail/IGCObject_DLambdaExpr.hpp>
@@ -63,6 +63,7 @@ namespace xo {
             // Expression
             // +- Constant
             // +- Variable
+            // +- VarRef
             // +- DefineExpr
             // +- ApplyExpr
             // +- LambdaExpr
@@ -77,13 +78,20 @@ namespace xo {
             FacetRegistry::register_impl<AGCObject, DVariable>();
             FacetRegistry::register_impl<APrintable, DVariable>();
 
+            FacetRegistry::register_impl<AExpression, DVarRef>();
+            FacetRegistry::register_impl<AGCObject, DVarRef>();
+            FacetRegistry::register_impl<APrintable, DVarRef>();
+
             FacetRegistry::register_impl<AExpression, DDefineExpr>();
+            //FacetRegistry::register_impl<AGCObject, DDefineExpr>();
             FacetRegistry::register_impl<APrintable, DDefineExpr>();
 
             FacetRegistry::register_impl<AExpression, DApplyExpr>();
+            FacetRegistry::register_impl<AGCObject, DApplyExpr>();
             FacetRegistry::register_impl<APrintable, DApplyExpr>();
 
             FacetRegistry::register_impl<AExpression, DLambdaExpr>();
+            //FacetRegistry::register_impl<AGCObject, DLambdaExpr>();
             FacetRegistry::register_impl<APrintable, DLambdaExpr>();
 
             FacetRegistry::register_impl<AExpression, DIfElseExpr>();
@@ -95,11 +103,13 @@ namespace xo {
             FacetRegistry::register_impl<APrintable, DSequenceExpr>();
 
             FacetRegistry::register_impl<ASymbolTable, DLocalSymtab>();
+            //FacetRegistry::register_impl<AGCObject, DLocalSymtab>();
             FacetRegistry::register_impl<APrintable, DLocalSymtab>();
 
             log && log(xtag("DUniqueString.tseq", typeseq::id<DUniqueString>()));
             log && log(xtag("DDefineExpr.tseq", typeseq::id<DDefineExpr>()));
             log && log(xtag("DVariable.tseq", typeseq::id<DVariable>()));
+            log && log(xtag("DVarRef.tseq", typeseq::id<DVarRef>()));
             log && log(xtag("DConstant.tseq", typeseq::id<DConstant>()));
             log && log(xtag("DApplyExpr.tseq", typeseq::id<DApplyExpr>()));
             log && log(xtag("DLambdaExpr.tseq", typeseq::id<DLambdaExpr>()));
@@ -108,7 +118,7 @@ namespace xo {
 
             log && log(xtag("DLocalSymtab.tseq", typeseq::id<DLocalSymtab>()));
 
-            log && log(xtag("AExpression.tqseq", typeseq::id<AExpression>()));
+            log && log(xtag("AExpression.tseq", typeseq::id<AExpression>()));
             log && log(xtag("ASymbolTable.tseq", typeseq::id<ASymbolTable>()));
 
             return true;