diff --git a/example/ex1/ex1.cpp b/example/ex1/ex1.cpp
index f5eb1d1d..cc642dcb 100644
--- a/example/ex1/ex1.cpp
+++ b/example/ex1/ex1.cpp
@@ -56,18 +56,18 @@ int
 main() {
     using xo::scope;
     using xo::jit::MachPipeline;
-    using xo::ast::make_constant;
-    using xo::ast::make_primitive;
-    using xo::ast::llvmintrinsic;
-    using xo::ast::make_apply;
-    using xo::ast::make_var;
-    using xo::ast::make_lambda;
+    using xo::scm::make_constant;
+    using xo::scm::make_primitive;
+    using xo::scm::llvmintrinsic;
+    using xo::scm::make_apply;
+    using xo::scm::make_var;
+    using xo::scm::make_lambda;
     using xo::reflect::Reflect;
     using xo::xtag;
     using std::cerr;
     using std::endl;
 
-    //using xo::ast::make_constant;
+    //using xo::scm::make_constant;
 
     static llvm::ExitOnError llvm_exit_on_err;
 
diff --git a/example/ex2_jit/ex2_jit.cpp b/example/ex2_jit/ex2_jit.cpp
index dc948afb..b0f32643 100644
--- a/example/ex2_jit/ex2_jit.cpp
+++ b/example/ex2_jit/ex2_jit.cpp
@@ -47,18 +47,18 @@ main() {
     using xo::scope;
     using xo::jit::MachPipeline;
     using xo::jit::activation_record;
-    using xo::ast::make_constant;
-    using xo::ast::make_primitive;
-    using xo::ast::llvmintrinsic;
-    using xo::ast::make_apply;
-    using xo::ast::make_var;
-    using xo::ast::make_lambda;
+    using xo::scm::make_constant;
+    using xo::scm::make_primitive;
+    using xo::scm::llvmintrinsic;
+    using xo::scm::make_apply;
+    using xo::scm::make_var;
+    using xo::scm::make_lambda;
     using xo::reflect::Reflect;
     using xo::xtag;
     using std::cerr;
     using std::endl;
 
-    //using xo::ast::make_constant;
+    //using xo::scm::make_constant;
 
     static llvm::ExitOnError llvm_exit_on_err;
 
diff --git a/include/xo/jit/MachPipeline.hpp b/include/xo/jit/MachPipeline.hpp
index 9839ebe3..829bd646 100644
--- a/include/xo/jit/MachPipeline.hpp
+++ b/include/xo/jit/MachPipeline.hpp
@@ -56,13 +56,13 @@ namespace xo {
         **/
         class MachPipeline : public ref::Refcount {
         public:
-            using Expression = xo::ast::Expression;
-            using Lambda = xo::ast::Lambda;
-            using GlobalEnv = xo::ast::GlobalEnv;
+            using Expression = xo::scm::Expression;
+            using Lambda = xo::scm::Lambda;
+            using GlobalEnv = xo::scm::GlobalEnv;
             using TypeDescr = xo::reflect::TypeDescr;
             using ExecutionSession = llvm::orc::ExecutionSession;
             using DataLayout = llvm::DataLayout;
-            //using ConstantInterface = xo::ast::ConstantInterface;
+            //using ConstantInterface = xo::scm::ConstantInterface;
 
         public:
             /* tracking KaleidoscopeJIT::Create() here.. */
@@ -109,8 +109,8 @@ namespace xo {
              *  @c llvm::Type instances are *immortal* (llvm interns them into opaque global lookup tables)
              **/
             llvm::Type * codegen_type(TypeDescr td);
-            llvm::Value * codegen_constant(bp<xo::ast::ConstantInterface> expr);
-            llvm::Function * codegen_primitive(bp<xo::ast::PrimitiveInterface> expr);
+            llvm::Value * codegen_constant(bp<xo::scm::ConstantInterface> expr);
+            llvm::Function * codegen_primitive(bp<xo::scm::PrimitiveInterface> expr);
 
             /** like @ref codegen_primitive , but create wrapper function that accepts (and discards)
              *  environment pointer as first argument.
@@ -118,7 +118,7 @@ namespace xo {
              *  Implementation consists of tail call to natural primitive, that skips the unused
              *  environment pointer
              **/
-            llvm::Function * codegen_primitive_wrapper(bp<xo::ast::PrimitiveInterface> expr,
+            llvm::Function * codegen_primitive_wrapper(bp<xo::scm::PrimitiveInterface> expr,
                                                        llvm::IRBuilder<> & ir_builder);
 
             /** Generate closure for invoking a primitive function.
@@ -126,17 +126,17 @@ namespace xo {
              *  to support function-pointer-like behavior for a target function
              *  that may resolve to primitive-or-lambda at runtime
              **/
-            llvm::Value * codegen_primitive_closure(bp<xo::ast::PrimitiveInterface> expr,
+            llvm::Value * codegen_primitive_closure(bp<xo::scm::PrimitiveInterface> expr,
                                                     llvm::IRBuilder<> & ir_builder);
 
-            llvm::Value * codegen_apply(bp<xo::ast::Apply> expr,
+            llvm::Value * codegen_apply(bp<xo::scm::Apply> expr,
                                         llvm::Value * envptr,
                                         llvm::IRBuilder<> & ir_builder);
             /* NOTE: codegen_lambda() needs to be reentrant too.
              *       for example can have a lambda in apply position.
              */
-            llvm::Function * codegen_lambda_decl(bp<xo::ast::Lambda> expr);
-            llvm::Function * codegen_lambda_defn(bp<xo::ast::Lambda> expr, llvm::IRBuilder<> & ir_builder);
+            llvm::Function * codegen_lambda_decl(bp<xo::scm::Lambda> expr);
+            llvm::Function * codegen_lambda_defn(bp<xo::scm::Lambda> expr, llvm::IRBuilder<> & ir_builder);
             /** Generate closure for invoking a lambda (user-defined function).
              *  See @ref MachPipeline::codegen_apply for invocation
              *  Same ABI as @ref MachPipeline::codegen_primitive_closure
@@ -147,13 +147,13 @@ namespace xo {
              *                  @ref MachPipeline::codegen_toplevel and friends are responsible for
              *                  assembling and propagating this.
              **/
-            llvm::Value * codegen_lambda_closure(bp<xo::ast::Lambda> lambda,
+            llvm::Value * codegen_lambda_closure(bp<xo::scm::Lambda> lambda,
                                                  llvm::Value * envptr,
                                                  llvm::IRBuilder<> & ir_builder);
-            llvm::Value * codegen_variable(bp<xo::ast::Variable> var,
+            llvm::Value * codegen_variable(bp<xo::scm::Variable> var,
                                            llvm::Value * envptr,
                                            llvm::IRBuilder<> & ir_builder);
-           llvm::Value * codegen_ifexpr(bp<xo::ast::IfExpr> ifexpr,
+           llvm::Value * codegen_ifexpr(bp<xo::scm::IfExpr> ifexpr,
                                          llvm::Value * envptr,
                                          llvm::IRBuilder<> & ir_builder);
 
diff --git a/include/xo/jit/activation_record.hpp b/include/xo/jit/activation_record.hpp
index ff59e9bf..ae834986 100644
--- a/include/xo/jit/activation_record.hpp
+++ b/include/xo/jit/activation_record.hpp
@@ -17,7 +17,7 @@
 
 namespace xo {
     namespace jit {
-        /** analagous to xo::ast::binding_path,
+        /** analagous to xo::scm::binding_path,
          *  but with locations renumbered to include only vars that belong to an explict runtime
          *  environment object;  in other words we exclude vars with stack-only storage
          **/
@@ -119,7 +119,7 @@ namespace xo {
          **/
         class activation_record {
         public:
-            using Lambda = xo::ast::Lambda;
+            using Lambda = xo::scm::Lambda;
             using TypeDescr = xo::reflect::TypeDescr;
 
         public:
diff --git a/include/xo/jit/type2llvm.hpp b/include/xo/jit/type2llvm.hpp
index f0efc87f..7801309f 100644
--- a/include/xo/jit/type2llvm.hpp
+++ b/include/xo/jit/type2llvm.hpp
@@ -20,8 +20,8 @@ namespace xo {
          **/
         struct type2llvm {
         public:
-            using FunctionInterface = xo::ast::FunctionInterface;
-            using Lambda = xo::ast::Lambda;
+            using FunctionInterface = xo::scm::FunctionInterface;
+            using Lambda = xo::scm::Lambda;
             using TypeDescr = xo::reflect::TypeDescr;
 
         public:
diff --git a/src/jit/MachPipeline.cpp b/src/jit/MachPipeline.cpp
index 85fcc7e6..462ed4a4 100644
--- a/src/jit/MachPipeline.cpp
+++ b/src/jit/MachPipeline.cpp
@@ -7,17 +7,17 @@
 #include <string>
 
 namespace xo {
-    using xo::ast::exprtype;
-    using xo::ast::Expression;
-    using xo::ast::ConstantInterface;
-    //using xo::ast::FunctionInterface;
-    using xo::ast::PrimitiveInterface;
-    using xo::ast::Lambda;
-    using xo::ast::Variable;
-    using xo::ast::Apply;
-    using xo::ast::IfExpr;
-    using xo::ast::GlobalEnv;
-    using xo::ast::llvmintrinsic;
+    using xo::scm::exprtype;
+    using xo::scm::Expression;
+    using xo::scm::ConstantInterface;
+    //using xo::scm::FunctionInterface;
+    using xo::scm::PrimitiveInterface;
+    using xo::scm::Lambda;
+    using xo::scm::Variable;
+    using xo::scm::Apply;
+    using xo::scm::IfExpr;
+    using xo::scm::GlobalEnv;
+    using xo::scm::llvmintrinsic;
     using xo::reflect::Reflect;
     using xo::reflect::StructMember;
     using xo::reflect::TypeDescr;
@@ -369,7 +369,7 @@ namespace xo {
         } /*codegen_primitive_wrapper*/
 
         llvm::Value *
-        MachPipeline::codegen_primitive_closure(bp<xo::ast::PrimitiveInterface> expr,
+        MachPipeline::codegen_primitive_closure(bp<xo::scm::PrimitiveInterface> expr,
                                                 llvm::IRBuilder<> & ir_builder)
         {
             constexpr bool c_debug_flag = true;
@@ -435,7 +435,7 @@ namespace xo {
                     /* we don't need any special checking here.
                      * already know (from xo-level checking) that pointer has the right type.
                      *
-                     * Specifically, xo::ast::Apply::make() requires the expression in function position
+                     * Specifically, xo::scm::Apply::make() requires the expression in function position
                      * have suitable function type.
                      *
                      * Now: we have an llvm::Value (fn_value) representing the pointer.
@@ -1026,7 +1026,7 @@ namespace xo {
              */
 
             /* WIP.  STRATEGY:
-             * - xo::ast::ClosureExpr (an expression that generates a closure)
+             * - xo::scm::ClosureExpr (an expression that generates a closure)
              *   closure = {lambda, env}
              *
              * - pass 1:
diff --git a/src/jit/MachPipeline.new.cpp b/src/jit/MachPipeline.new.cpp
index c4faff4a..7a03e4a0 100644
--- a/src/jit/MachPipeline.new.cpp
+++ b/src/jit/MachPipeline.new.cpp
@@ -4,16 +4,16 @@
 #include <string>
 
 namespace xo {
-    using xo::ast::exprtype;
-    using xo::ast::Expression;
-    using xo::ast::ConstantInterface;
-    //using xo::ast::FunctionInterface;
-    using xo::ast::PrimitiveInterface;
-    using xo::ast::Lambda;
-    using xo::ast::Variable;
-    using xo::ast::Apply;
-    using xo::ast::IfExpr;
-    using xo::ast::llvmintrinsic;
+    using xo::scm::exprtype;
+    using xo::scm::Expression;
+    using xo::scm::ConstantInterface;
+    //using xo::scm::FunctionInterface;
+    using xo::scm::PrimitiveInterface;
+    using xo::scm::Lambda;
+    using xo::scm::Variable;
+    using xo::scm::Apply;
+    using xo::scm::IfExpr;
+    using xo::scm::llvmintrinsic;
     using xo::reflect::Reflect;
     using xo::reflect::StructMember;
     using xo::reflect::TypeDescr;
@@ -465,7 +465,7 @@ namespace xo {
                     /* we don't need any special checking here.
                      * already know (from xo-level checking) that pointer has the right type.
                      *
-                     * Specifically, xo::ast::Apply::make() requires the expression in function position
+                     * Specifically, xo::scm::Apply::make() requires the expression in function position
                      * have suitable function type.
                      *
                      * Now: we have an llvm::Value (fn_value) representing the pointer.
diff --git a/src/jit/MachPipeline.orig.cpp b/src/jit/MachPipeline.orig.cpp
index 69cf0d02..786ca581 100644
--- a/src/jit/MachPipeline.orig.cpp
+++ b/src/jit/MachPipeline.orig.cpp
@@ -4,16 +4,16 @@
 #include <string>
 
 namespace xo {
-    using xo::ast::exprtype;
-    using xo::ast::Expression;
-    using xo::ast::ConstantInterface;
-    //using xo::ast::FunctionInterface;
-    using xo::ast::PrimitiveInterface;
-    using xo::ast::Lambda;
-    using xo::ast::Variable;
-    using xo::ast::Apply;
-    using xo::ast::IfExpr;
-    using xo::ast::llvmintrinsic;
+    using xo::scm::exprtype;
+    using xo::scm::Expression;
+    using xo::scm::ConstantInterface;
+    //using xo::scm::FunctionInterface;
+    using xo::scm::PrimitiveInterface;
+    using xo::scm::Lambda;
+    using xo::scm::Variable;
+    using xo::scm::Apply;
+    using xo::scm::IfExpr;
+    using xo::scm::llvmintrinsic;
     using xo::reflect::Reflect;
     using xo::reflect::StructMember;
     using xo::reflect::TypeDescr;
@@ -465,7 +465,7 @@ namespace xo {
                     /* we don't need any special checking here.
                      * already know (from xo-level checking) that pointer has the right type.
                      *
-                     * Specifically, xo::ast::Apply::make() requires the expression in function position
+                     * Specifically, xo::scm::Apply::make() requires the expression in function position
                      * have suitable function type.
                      *
                      * Now: we have an llvm::Value (fn_value) representing the pointer.
diff --git a/utest/MachPipeline.test.cpp b/utest/MachPipeline.test.cpp
index 5cf81227..f615427a 100644
--- a/utest/MachPipeline.test.cpp
+++ b/utest/MachPipeline.test.cpp
@@ -10,13 +10,13 @@
 
 namespace xo {
     using xo::jit::MachPipeline;
-    using xo::ast::make_apply;
-    using xo::ast::make_var;
-    using xo::ast::make_primitive;
-    using xo::ast::llvmintrinsic;
-    using xo::ast::Expression;
-    using xo::ast::Lambda;
-    using xo::ast::exprtype;
+    using xo::scm::make_apply;
+    using xo::scm::make_var;
+    using xo::scm::make_primitive;
+    using xo::scm::llvmintrinsic;
+    using xo::scm::Expression;
+    using xo::scm::Lambda;
+    using xo::scm::exprtype;
     using xo::reflect::Reflect;
     using xo::reflect::reflect_struct;
     using xo::ref::brw;