diff --git a/xo-interpreter2/include/xo/interpreter2/interpreter2_register_primitives.hpp b/xo-interpreter2/include/xo/interpreter2/interpreter2_register_primitives.hpp
index 1946969a..5d3f0fb1 100644
--- a/xo-interpreter2/include/xo/interpreter2/interpreter2_register_primitives.hpp
+++ b/xo-interpreter2/include/xo/interpreter2/interpreter2_register_primitives.hpp
@@ -12,6 +12,7 @@ namespace xo {
     namespace scm {
         /** Register primitive-factories **/
         bool interpreter2_register_primitives(obj<xo::mm::AAllocator> gc,
+                                              StringTable * stbl,
                                               InstallSink sink,
                                               InstallFlags flags);
     }
diff --git a/xo-interpreter2/src/interpreter2/interpreter2_register_primitives.cpp b/xo-interpreter2/src/interpreter2/interpreter2_register_primitives.cpp
index 17512f4b..9b165b17 100644
--- a/xo-interpreter2/src/interpreter2/interpreter2_register_primitives.cpp
+++ b/xo-interpreter2/src/interpreter2/interpreter2_register_primitives.cpp
@@ -52,12 +52,11 @@ namespace xo {
 
         bool
         interpreter2_register_primitives(obj<xo::mm::AAllocator> mm,
+                                         StringTable * stbl,
                                          InstallSink sink,
                                          InstallFlags flags)
         {
-            (void)mm;
-            (void)sink;
-            (void)flags;
+            (void)stbl;
 
             scope log(XO_DEBUG(true));
 
diff --git a/xo-numeric/include/xo/numeric/numeric_register_primitives.hpp b/xo-numeric/include/xo/numeric/numeric_register_primitives.hpp
index 18a594be..c4b0bd7b 100644
--- a/xo-numeric/include/xo/numeric/numeric_register_primitives.hpp
+++ b/xo-numeric/include/xo/numeric/numeric_register_primitives.hpp
@@ -12,6 +12,7 @@ namespace xo {
     namespace scm {
         /** Register primitive factories with primitive registry **/
         bool numeric_register_primitives(obj<xo::mm::AAllocator> mm,
+                                         StringTable * stbl,
                                          InstallSink sink,
                                          InstallFlags flags);
     }
diff --git a/xo-numeric/src/numeric/numeric_register_primitives.cpp b/xo-numeric/src/numeric/numeric_register_primitives.cpp
index b2da4d9e..aa4a24d0 100644
--- a/xo-numeric/src/numeric/numeric_register_primitives.cpp
+++ b/xo-numeric/src/numeric/numeric_register_primitives.cpp
@@ -49,8 +49,11 @@ namespace xo {
         }
 
         bool
-        numeric_register_primitives(obj<AAllocator> mm, InstallSink sink, InstallFlags flags)
+        numeric_register_primitives(obj<AAllocator> mm, StringTable * stbl,
+                                    InstallSink sink, InstallFlags flags)
         {
+            (void)stbl;
+
             scope log(XO_DEBUG(true));
 
             bool ok = true;
diff --git a/xo-object2/include/xo/object2/DArray.hpp b/xo-object2/include/xo/object2/DArray.hpp
index 55d5e068..332d126a 100644
--- a/xo-object2/include/xo/object2/DArray.hpp
+++ b/xo-object2/include/xo/object2/DArray.hpp
@@ -72,7 +72,7 @@ namespace xo {
              *    Darray * v = DArray::array(mm, e1, e2, e3);
              **/
             template <typename... Args>
-                requires (std::same_as<Args, obj<AGCObject>> && ...)
+                requires (std::convertible_to<Args, obj<AGCObject>> && ...)
             static DArray * array(obj<AAllocator> mm, Args... args);
 
             ///@}
@@ -170,7 +170,7 @@ namespace xo {
         };
 
         template <typename... Args>
-            requires (std::same_as<Args, obj<DArray::AGCObject>> && ...)
+            requires (std::convertible_to<Args, obj<DArray::AGCObject>> && ...)
         DArray *
         DArray::array(obj<AAllocator> mm, Args... args)
         {
diff --git a/xo-procedure2/include/xo/procedure2/ObjectPrimitives.hpp b/xo-procedure2/include/xo/procedure2/ObjectPrimitives.hpp
index 2fc31766..696fc295 100644
--- a/xo-procedure2/include/xo/procedure2/ObjectPrimitives.hpp
+++ b/xo-procedure2/include/xo/procedure2/ObjectPrimitives.hpp
@@ -24,16 +24,20 @@ namespace xo {
 
         public:
             /** create primitive: report current working directory **/
-            static DPrimitive_gco_0 * make_cwd_pm(obj<AAllocator> mm);
+            static DPrimitive_gco_0 * make_cwd_pm(obj<AAllocator> mm,
+                                                  StringTable * stbl);
 
             /** create primitive: fetch nth element of a sequence **/
-            static DPrimitive_gco_2_gco_gco * make_nth_pm(obj<AAllocator> mm);
+            static DPrimitive_gco_2_gco_gco * make_nth_pm(obj<AAllocator> mm,
+                                                          StringTable * stbl);
 
             /** create primitive: create cons cell **/
-            static DPrimitive_gco_2_gco_gco * make_cons_pm(obj<AAllocator> mm);
+            static DPrimitive_gco_2_gco_gco * make_cons_pm(obj<AAllocator> mm,
+                                                           StringTable * stbl);
 
             /** create primitive for creating a dictionary instance **/
-            static DPrimitive_gco_0 * make_dict_make_pm(obj<AAllocator> mm);
+            static DPrimitive_gco_0 * make_dict_make_pm(obj<AAllocator> mm,
+                                                        StringTable * stbl);
 
             /** create primitive for creating a dictionary instance **/
             static DPrimitive_gco_2_dict_string * make_dict_lookup_pm(obj<AAllocator> mm);
diff --git a/xo-procedure2/include/xo/procedure2/PrimitiveRegistry.hpp b/xo-procedure2/include/xo/procedure2/PrimitiveRegistry.hpp
index 6f1f67ea..a4e24e2a 100644
--- a/xo-procedure2/include/xo/procedure2/PrimitiveRegistry.hpp
+++ b/xo-procedure2/include/xo/procedure2/PrimitiveRegistry.hpp
@@ -61,6 +61,7 @@ namespace xo {
              *  to InstallSink sink.
              **/
             using InstallSource = std::function<bool (obj<AAllocator> mm,
+                                                      StringTable * stbl,
                                                       InstallSink sink,
                                                       InstallFlags flags)>;
 
@@ -72,9 +73,11 @@ namespace xo {
             void register_primitives(InstallSource source_fn);
 
             /** create primitives using memory from @p mm,
+             *  with global strings in @p stbl.
              *  delivering each primitive to @p sink.
              **/
             bool install_primitives(obj<AAllocator> mm,
+                                    StringTable * stbl,
                                     InstallSink sink,
                                     InstallFlags flags);
 
diff --git a/xo-procedure2/include/xo/procedure2/procedure2_register_primitives.hpp b/xo-procedure2/include/xo/procedure2/procedure2_register_primitives.hpp
index 69237697..396f645f 100644
--- a/xo-procedure2/include/xo/procedure2/procedure2_register_primitives.hpp
+++ b/xo-procedure2/include/xo/procedure2/procedure2_register_primitives.hpp
@@ -12,6 +12,7 @@ namespace xo {
     namespace scm {
         /** Register primitive-factories **/
         bool procedure2_register_primitives(obj<xo::mm::AAllocator> gc,
+                                            StringTable * stbl,
                                             InstallSink sink,
                                             InstallFlags flags);
     }
diff --git a/xo-procedure2/src/procedure2/ObjectPrimitives.cpp b/xo-procedure2/src/procedure2/ObjectPrimitives.cpp
index c247ab8c..d52c5304 100644
--- a/xo-procedure2/src/procedure2/ObjectPrimitives.cpp
+++ b/xo-procedure2/src/procedure2/ObjectPrimitives.cpp
@@ -9,6 +9,10 @@
 #include <xo/object2/Sequence.hpp>
 #include <xo/object2/List.hpp>
 #include <xo/object2/Integer.hpp>
+#include <xo/type/FunctionType.hpp>
+#include <xo/type/ListType.hpp>
+#include <xo/type/TypeVarRef.hpp>
+#include <xo/type/AtomicType.hpp>
 #include <xo/printable2/Printable.hpp>
 #include <xo/stringtable2/String.hpp>
 #include <unistd.h> // for getcwd()
@@ -35,9 +39,15 @@ namespace xo {
         }
 
         DPrimitive_gco_0 *
-        ObjectPrimitives::make_cwd_pm(obj<AAllocator> mm)
+        ObjectPrimitives::make_cwd_pm(obj<AAllocator> mm, StringTable * stbl)
         {
-            return DPrimitive_gco_0::_make(mm, "cwd", &xfer_cwd);
+            (void)stbl;
+
+            auto str_ty = DAtomicType::make(mm, Metatype::t_str());
+            auto cwd_ty
+                = obj<AType,DFunctionType>(DFunctionType::_make(mm, str_ty));
+
+            return DPrimitive_gco_0::_make(mm, "cwd", cwd_ty, &xfer_cwd);
         }
 
         // ----- nth -----
@@ -59,9 +69,20 @@ namespace xo {
         }
 
         DPrimitive_gco_2_gco_gco *
-        ObjectPrimitives::make_nth_pm(obj<AAllocator> mm)
+        ObjectPrimitives::make_nth_pm(obj<AAllocator> mm, StringTable * stbl)
         {
-            return DPrimitive_gco_2_gco_gco::_make(mm, "nth", &xfer_nth);
+            auto T_ty = DTypeVarRef::make(mm, stbl->intern("T"));
+            auto list_T_ty = DListType::make(mm, T_ty);
+            auto int_ty = DAtomicType::make(mm, Metatype::t_integer());
+            /** nth_ty: list<T> x int -> T **/
+            auto nth_ty
+                = obj<AType,DFunctionType>
+                (DFunctionType::_make(mm,
+                                      T_ty,
+                                      list_T_ty,
+                                      int_ty));
+
+            return DPrimitive_gco_2_gco_gco::_make(mm, "nth", nth_ty, &xfer_nth);
         }
 
         // ----- cons -----
@@ -75,17 +96,24 @@ namespace xo {
 
             auto cdr_list = obj<AGCObject,DList>::from(cdr);
 
-            //auto T = DTypeVarRef::_make(rcx.allocator(), "T");
-
             return DList::cons(rcx.allocator(),
                                car,
                                cdr_list.data());
         }
 
         DPrimitive_gco_2_gco_gco *
-        ObjectPrimitives::make_cons_pm(obj<AAllocator> mm)
+        ObjectPrimitives::make_cons_pm(obj<AAllocator> mm, StringTable * stbl)
         {
-            return DPrimitive_gco_2_gco_gco::_make(mm, "cons", &xfer_cons);
+            auto T_ty = DTypeVarRef::make(mm, stbl->intern("T"));
+            auto list_T_ty = DListType::make(mm, T_ty);
+            /** cons_ty: T x list<T> -> list<T> **/
+            auto cons_ty
+                = obj<AType,DFunctionType>(DFunctionType::_make(mm,
+                                                                list_T_ty,
+                                                                T_ty,
+                                                                list_T_ty));
+
+            return DPrimitive_gco_2_gco_gco::_make(mm, "cons", cons_ty, &xfer_cons);
         }
 
         // ----- dict_make -----
@@ -98,9 +126,17 @@ namespace xo {
         }
 
         DPrimitive_gco_0 *
-        ObjectPrimitives::make_dict_make_pm(obj<AAllocator> mm)
+        ObjectPrimitives::make_dict_make_pm(obj<AAllocator> mm,
+                                            StringTable * stbl)
         {
-            return DPrimitive_gco_0::_make(mm, "dict_make", &xfer_dict_make);
+            (void)stbl;
+
+            // nit: technically better to use empty struct type here
+            auto dict_ty = DAtomicType::make(mm, Metatype::t_dict());
+            auto pm_ty = obj<AType,DFunctionType>(DFunctionType::_make(mm,
+                                                                       dict_ty));
+
+            return DPrimitive_gco_0::_make(mm, "dict_make", pm_ty, &xfer_dict_make);
         }
 
         // ----- dict_at -----
diff --git a/xo-procedure2/src/procedure2/PrimitiveRegistry.cpp b/xo-procedure2/src/procedure2/PrimitiveRegistry.cpp
index e62b6794..420a435e 100644
--- a/xo-procedure2/src/procedure2/PrimitiveRegistry.cpp
+++ b/xo-procedure2/src/procedure2/PrimitiveRegistry.cpp
@@ -26,6 +26,7 @@ namespace xo {
 
         bool
         PrimitiveRegistry::install_primitives(obj<AAllocator> mm,
+                                              StringTable * stbl,
                                               InstallSink sink,
                                               InstallFlags flags)
         {
@@ -40,7 +41,7 @@ namespace xo {
             for (const auto & fn : init_seq_v_) {
                 log && log("do install fn (", i+1, "/", n, ")");
 
-                ok = ok & fn(mm, sink, flags);
+                ok = ok & fn(mm, stbl, sink, flags);
                 ++i;
             }
 
diff --git a/xo-procedure2/src/procedure2/procedure2_register_primitives.cpp b/xo-procedure2/src/procedure2/procedure2_register_primitives.cpp
index fee0bd91..eed4cf55 100644
--- a/xo-procedure2/src/procedure2/procedure2_register_primitives.cpp
+++ b/xo-procedure2/src/procedure2/procedure2_register_primitives.cpp
@@ -54,6 +54,7 @@ namespace xo {
 
         bool
         procedure2_register_primitives(obj<xo::mm::AAllocator> mm,
+                                       StringTable * stbl,
                                        InstallSink sink,
                                        InstallFlags flags)
         {
@@ -61,10 +62,10 @@ namespace xo {
 
             bool ok = true;
 
-            ok = ok & install_aux(sink, ObjectPrimitives::make_cwd_pm(mm), flags);
-            ok = ok & install_aux(sink, ObjectPrimitives::make_nth_pm(mm), flags);
-            ok = ok & install_aux(sink, ObjectPrimitives::make_cons_pm(mm), flags);
-            ok = ok & install_aux(sink, ObjectPrimitives::make_dict_make_pm(mm), flags);
+            ok = ok & install_aux(sink, ObjectPrimitives::make_cwd_pm(mm, stbl), flags);
+            ok = ok & install_aux(sink, ObjectPrimitives::make_nth_pm(mm, stbl), flags);
+            ok = ok & install_aux(sink, ObjectPrimitives::make_cons_pm(mm, stbl), flags);
+            ok = ok & install_aux(sink, ObjectPrimitives::make_dict_make_pm(mm, stbl), flags);
             ok = ok & install_aux(sink, ObjectPrimitives::make_dict_lookup_pm(mm), flags);
             ok = ok & install_aux(sink, ObjectPrimitives::make_dict_upsert_pm(mm), flags);
             ok = ok & install_aux(sink, ObjectPrimitives::make_fn_n_args_pm(mm), flags);
diff --git a/xo-reader2/src/reader2/ParserStateMachine.cpp b/xo-reader2/src/reader2/ParserStateMachine.cpp
index 5e6b4164..6ab2097b 100644
--- a/xo-reader2/src/reader2/ParserStateMachine.cpp
+++ b/xo-reader2/src/reader2/ParserStateMachine.cpp
@@ -71,6 +71,7 @@ namespace xo {
 
                 PrimitiveRegistry::instance()
                     .install_primitives(mm,
+                                        &stringtable,
                                         sink,
                                         pm_install_flags);
 
diff --git a/xo-type/include/xo/type/DFunctionType.hpp b/xo-type/include/xo/type/DFunctionType.hpp
index 7090a60b..51568bf5 100644
--- a/xo-type/include/xo/type/DFunctionType.hpp
+++ b/xo-type/include/xo/type/DFunctionType.hpp
@@ -32,17 +32,27 @@ namespace xo {
              *  for a function with return type @p ret_type and arguments @p args
              **/
             template <typename... Args>
-                requires (std::same_as<Args, obj<AType>> && ...)
+                requires (std::convertible_to<Args, obj<AType>> && ...)
             explicit DFunctionType(obj<AAllocator> mm, obj<AType> ret_type, Args... args);
 
             /** create instance using memory from @p mm,
              *  for a function with return type @p ret_type and arguments @p args
              **/
             template <typename... Args>
-                requires (std::same_as<Args, obj<AType>> && ...)
+                requires (std::convertible_to<Args, obj<AType>> && ...)
             static DFunctionType * _make(obj<AAllocator> mm,
                                          obj<AType> ret_type, Args... args);
 
+#ifdef NOT_USING
+            /** create instance using memory from @p mm
+             *  for function with return type @p ret_type and arguments @p args
+             **/
+            template <typename... Args>
+            requires (std::same_as<Args, obj<AType>> && ...)
+            static obj<AType,DFunctionType> make(obj<AAllocator> mm,
+                                                 obj<AType> ret_type, Args... args);
+#endif
+
             ///@}
             /** @defgroup xo-scm-arraytype-type-facet **/
             ///@{
@@ -72,14 +82,14 @@ namespace xo {
         };
 
         template <typename... Args>
-            requires (std::same_as<Args, obj<AType>> && ...)
+            requires (std::convertible_to<Args, obj<AType>> && ...)
         DFunctionType::DFunctionType(obj<AAllocator> mm, obj<AType> return_type, Args... args)
             : return_type_{return_type},
-              arg_types_{DArray::array(mm, args...)}
+              arg_types_{DArray::array(mm, args.template to_facet<AGCObject>()...)}
         {}
 
         template <typename... Args>
-            requires (std::same_as<Args, obj<AType>> && ...)
+            requires (std::convertible_to<Args, obj<AType>> && ...)
         DFunctionType *
         DFunctionType::_make(obj<AAllocator> mm, obj<AType> ret_type, Args... args)
         {
@@ -88,6 +98,18 @@ namespace xo {
             return new (mem) DFunctionType(mm, ret_type, args...);
         }
 
+#ifdef NOT_USING
+        template <typename... Args>
+            requires (std::same_as<Args, obj<AType>> && ...)
+        obj<AType,DFunctionType>
+        DFunctionType::make(obj<AAllocator> mm, obj<AType> ret_type, Args... args)
+        {
+            void * mem = mm.alloc_for<DFunctionType>();
+
+            return obj<AType,DFunctionType>(_make(mm, ret_type, args...));
+        }
+#endif
+
     } /*namespace scm*/
 } /*namespace xo*/
 
diff --git a/xo-type/include/xo/type/Metatype.hpp b/xo-type/include/xo/type/Metatype.hpp
index 30952df8..0b0aeefe 100644
--- a/xo-type/include/xo/type/Metatype.hpp
+++ b/xo-type/include/xo/type/Metatype.hpp
@@ -39,8 +39,13 @@ namespace xo {
                 t_function,
                 /* struct<a:T,b:U,..> */
                 t_struct,
+                /* dicttionary: like struct, but w/ dynamic key/value pairs  */
+                t_dict,
 
-                /* any numeric type: i16|i32|i64|f32|f64 */
+                /** any integer type: i16|i32|i64 **/
+                t_integer,
+
+                /** any numeric type: i16|i32|i64|f32|f64 **/
                 t_numeric,
 
                 /* any type at all */
@@ -66,7 +71,9 @@ namespace xo {
             static Metatype t_array()    { return Metatype(code::t_array);    }
             static Metatype t_function() { return Metatype(code::t_function); }
             static Metatype t_struct()   { return Metatype(code::t_struct);   }
+            static Metatype t_dict()     { return Metatype(code::t_dict);     }
 
+            static Metatype t_integer()  { return Metatype(code::t_integer);  }
             static Metatype t_numeric()  { return Metatype(code::t_numeric);  }
             static Metatype t_any()      { return Metatype(code::t_any);      }
 
diff --git a/xo-type/src/type/Metatype.cpp b/xo-type/src/type/Metatype.cpp
index 9e50f11a..be42f61c 100644
--- a/xo-type/src/type/Metatype.cpp
+++ b/xo-type/src/type/Metatype.cpp
@@ -28,7 +28,9 @@ namespace xo {
             case code::t_array:    return "array";
             case code::t_function: return "function";
             case code::t_struct:   return "struct";
+            case code::t_dict:     return "dict";
 
+            case code::t_integer:  return "integer";
             case code::t_numeric:  return "numeric";
             case code::t_any:      return "any";
             }
@@ -68,7 +70,11 @@ namespace xo {
                 return false;
             case code::t_struct:
                 return false;
+            case code::t_dict:
+                return true;
 
+            case code::t_integer:
+                return true;
             case code::t_numeric:
                 return true;
             case code::t_any: