diff --git a/examples/exprreplxx/exprreplxx.cpp b/examples/exprreplxx/exprreplxx.cpp
index 862a1d05..db1f3e1c 100644
--- a/examples/exprreplxx/exprreplxx.cpp
+++ b/examples/exprreplxx/exprreplxx.cpp
@@ -61,7 +61,7 @@ int
 main() {
     using namespace replxx;
     using namespace xo::scm;
-    using xo::ast::Expression;
+    using xo::scm::Expression;
     using xo::print::ppconfig;
     using xo::print::ppstate_standalone;
     using xo::rp;
diff --git a/include/xo/reader/apply_xs.hpp b/include/xo/reader/apply_xs.hpp
index cf57b9ab..9c4cf99f 100644
--- a/include/xo/reader/apply_xs.hpp
+++ b/include/xo/reader/apply_xs.hpp
@@ -57,7 +57,7 @@ namespace xo {
          */
         class apply_xs : public exprstate {
         public:
-            using Apply = xo::ast::Apply;
+            using Apply = xo::scm::Apply;
 
         public:
             explicit apply_xs();
@@ -109,7 +109,9 @@ namespace xo {
     } /*namespace scm */
 
     namespace print {
+#ifndef ppdetail_atomic
         PPDETAIL_ATOMIC(xo::scm::applyexprstatetype);
+#endif
     }
 } /*namespace xo*/
 
diff --git a/include/xo/reader/define_xs.hpp b/include/xo/reader/define_xs.hpp
index 76e1bcd8..47a4712d 100644
--- a/include/xo/reader/define_xs.hpp
+++ b/include/xo/reader/define_xs.hpp
@@ -67,8 +67,8 @@ namespace xo {
          **/
         class define_xs : public exprstate {
         public:
-            using DefineExprAccess = xo::ast::DefineExprAccess;
-            using ConvertExprAccess = xo::ast::ConvertExprAccess;
+            using DefineExprAccess = xo::scm::DefineExprAccess;
+            using ConvertExprAccess = xo::scm::ConvertExprAccess;
 
         public:
             define_xs(rp<DefineExprAccess> def_expr);
diff --git a/include/xo/reader/envframe.hpp b/include/xo/reader/envframe.hpp
index a949379e..237b1402 100644
--- a/include/xo/reader/envframe.hpp
+++ b/include/xo/reader/envframe.hpp
@@ -21,9 +21,9 @@ namespace xo {
          **/
         class envframe {
         public:
-            using Environment = xo::ast::Environment;
-            using LocalEnv    = xo::ast::LocalEnv;
-            using Variable    = xo::ast::Variable;
+            using Environment = xo::scm::Environment;
+            using LocalEnv    = xo::scm::LocalEnv;
+            using Variable    = xo::scm::Variable;
 
         public:
             envframe() = default;
diff --git a/include/xo/reader/envframestack.hpp b/include/xo/reader/envframestack.hpp
index 9e6a1d6f..81de3ec3 100644
--- a/include/xo/reader/envframestack.hpp
+++ b/include/xo/reader/envframestack.hpp
@@ -14,8 +14,8 @@ namespace xo {
          **/
         class envframestack {
         public:
-            using LocalEnv     = xo::ast::LocalEnv;
-            using Variable     = xo::ast::Variable;
+            using LocalEnv     = xo::scm::LocalEnv;
+            using Variable     = xo::scm::Variable;
             using ppstate      = xo::print::ppstate;
             using ppindentinfo = xo::print::ppindentinfo;
 
diff --git a/include/xo/reader/expect_formal_arglist_xs.hpp b/include/xo/reader/expect_formal_arglist_xs.hpp
index ee3a7a48..509fe194 100644
--- a/include/xo/reader/expect_formal_arglist_xs.hpp
+++ b/include/xo/reader/expect_formal_arglist_xs.hpp
@@ -48,7 +48,7 @@ namespace xo {
          **/
         class expect_formal_arglist_xs : public exprstate {
         public:
-            using Variable = xo::ast::Variable;
+            using Variable = xo::scm::Variable;
 
         public:
             expect_formal_arglist_xs();
diff --git a/include/xo/reader/exprstate.hpp b/include/xo/reader/exprstate.hpp
index 24e5f6d0..f3b00d51 100644
--- a/include/xo/reader/exprstate.hpp
+++ b/include/xo/reader/exprstate.hpp
@@ -95,9 +95,9 @@ namespace xo {
          **/
         class exprstate {
         public:
-            using Expression = xo::ast::Expression;
-            using Variable = xo::ast::Variable;
-            using exprtype = xo::ast::exprtype;
+            using Expression = xo::scm::Expression;
+            using Variable = xo::scm::Variable;
+            using exprtype = xo::scm::exprtype;
             using token_type = token<char>;
             using TypeDescr = xo::reflect::TypeDescr;
 
diff --git a/include/xo/reader/if_else_xs.hpp b/include/xo/reader/if_else_xs.hpp
index 04efb75c..05ab0c60 100644
--- a/include/xo/reader/if_else_xs.hpp
+++ b/include/xo/reader/if_else_xs.hpp
@@ -51,7 +51,7 @@ namespace xo {
          **/
         class if_else_xs : public exprstate {
         public:
-            using IfExprAccess = xo::ast::IfExprAccess;
+            using IfExprAccess = xo::scm::IfExprAccess;
 
         public:
             if_else_xs(rp<IfExprAccess> if_expr);
@@ -100,7 +100,9 @@ namespace xo {
     } /*namespace scm*/
 
     namespace print {
+#ifndef ppdetail_atomic
         PPDETAIL_ATOMIC(xo::scm::ifexprstatetype);
+#endif
     }
 } /*namespace xo*/
 
diff --git a/include/xo/reader/lambda_xs.hpp b/include/xo/reader/lambda_xs.hpp
index b51ac191..91118447 100644
--- a/include/xo/reader/lambda_xs.hpp
+++ b/include/xo/reader/lambda_xs.hpp
@@ -55,8 +55,8 @@ namespace xo {
          **/
         class lambda_xs : public exprstate {
         public:
-            using Environment = xo::ast::Environment;
-            using LocalEnv = xo::ast::LocalEnv;
+            using Environment = xo::scm::Environment;
+            using LocalEnv = xo::scm::LocalEnv;
 
         public:
             lambda_xs();
@@ -111,7 +111,9 @@ namespace xo {
     } /*namespace scm*/
 
     namespace print {
+#ifndef ppdetail_atomic
         PPDETAIL_ATOMIC(xo::scm::lambdastatetype);
+#endif
     }
 } /*namespace xo*/
 
diff --git a/include/xo/reader/let1_xs.hpp b/include/xo/reader/let1_xs.hpp
index ca6f237c..3377081f 100644
--- a/include/xo/reader/let1_xs.hpp
+++ b/include/xo/reader/let1_xs.hpp
@@ -12,7 +12,7 @@ namespace xo {
     namespace scm {
         class let1_xs : public exprstate {
         public:
-            using LocalEnv = xo::ast::LocalEnv;
+            using LocalEnv = xo::scm::LocalEnv;
 
         public:
             /** given local definition equivalent to
diff --git a/include/xo/reader/parser.hpp b/include/xo/reader/parser.hpp
index c45278a1..6f6b459b 100644
--- a/include/xo/reader/parser.hpp
+++ b/include/xo/reader/parser.hpp
@@ -153,7 +153,7 @@ namespace xo {
          **/
         class parser {
         public:
-            using Expression = xo::ast::Expression;
+            using Expression = xo::scm::Expression;
             using token_type = exprstate::token_type; // token<char>;
 
         public:
diff --git a/include/xo/reader/parser_result.hpp b/include/xo/reader/parser_result.hpp
index 204a29a6..8ccee992 100644
--- a/include/xo/reader/parser_result.hpp
+++ b/include/xo/reader/parser_result.hpp
@@ -19,7 +19,7 @@ namespace xo {
         };
 
         struct parser_result {
-            using Expression = xo::ast::Expression;
+            using Expression = xo::scm::Expression;
 
         public:
             parser_result() = default;
diff --git a/include/xo/reader/parserstatemachine.hpp b/include/xo/reader/parserstatemachine.hpp
index d243bbe2..cecf5c95 100644
--- a/include/xo/reader/parserstatemachine.hpp
+++ b/include/xo/reader/parserstatemachine.hpp
@@ -22,9 +22,9 @@ namespace xo {
          **/
         class parserstatemachine {
         public:
-            using Expression = xo::ast::Expression;
-            using Variable = xo::ast::Variable;
-            using LocalEnv = xo::ast::LocalEnv;
+            using Expression = xo::scm::Expression;
+            using Variable = xo::scm::Variable;
+            using LocalEnv = xo::scm::LocalEnv;
             using token_type = token<char>;
 
         public:
diff --git a/include/xo/reader/reader.hpp b/include/xo/reader/reader.hpp
index 3283065f..69c42885 100644
--- a/include/xo/reader/reader.hpp
+++ b/include/xo/reader/reader.hpp
@@ -17,7 +17,7 @@ namespace xo {
          *  @brief Result object returned from reader::read_expr
          **/
         struct reader_result {
-            using Expression = xo::ast::Expression;
+            using Expression = xo::scm::Expression;
             using span_type = span<const char>;
 
             reader_result(rp<Expression> expr, span_type rem, std::size_t psz, const reader_error & error)
diff --git a/include/xo/reader/sequence_xs.hpp b/include/xo/reader/sequence_xs.hpp
index 22e9a325..fa648c95 100644
--- a/include/xo/reader/sequence_xs.hpp
+++ b/include/xo/reader/sequence_xs.hpp
@@ -9,14 +9,14 @@
 #include <vector>
 
 namespace xo {
-    namespace ast { class Sequence; }
-    namespace ast { class Lambda; }
+    namespace scm { class Sequence; }
+    namespace scm { class Lambda; }
 
     namespace scm {
         class sequence_xs : public exprstate {
         public:
-            using Sequence = xo::ast::Sequence;
-            using Lambda = xo::ast::Lambda;
+            using Sequence = xo::scm::Sequence;
+            using Lambda = xo::scm::Lambda;
 
         public:
             /** start parsing a sequence-expr.
diff --git a/src/reader/envframe.cpp b/src/reader/envframe.cpp
index 3e0e5858..985bc1c6 100644
--- a/src/reader/envframe.cpp
+++ b/src/reader/envframe.cpp
@@ -7,7 +7,7 @@
 #include "xo/indentlog/print/vector.hpp"
 
 namespace xo {
-    using xo::ast::Variable;
+    using xo::scm::Variable;
 
     namespace scm {
 #ifdef OBSOLETE
diff --git a/src/reader/envframestack.cpp b/src/reader/envframestack.cpp
index 9db3146a..3dff60da 100644
--- a/src/reader/envframestack.cpp
+++ b/src/reader/envframestack.cpp
@@ -8,8 +8,8 @@
 #include "pretty_localenv.hpp"
 
 namespace xo {
-    using xo::ast::LocalEnv;
-    using xo::ast::Variable;
+    using xo::scm::LocalEnv;
+    using xo::scm::Variable;
 
     namespace scm {
         bp<LocalEnv>
diff --git a/src/reader/expect_expr_xs.cpp b/src/reader/expect_expr_xs.cpp
index 37a33bde..5bf7571a 100644
--- a/src/reader/expect_expr_xs.cpp
+++ b/src/reader/expect_expr_xs.cpp
@@ -17,7 +17,7 @@
 #include "xo/expression/pretty_expression.hpp"
 
 namespace xo {
-    using xo::ast::Constant;
+    using xo::scm::Constant;
 
     namespace scm {
 
diff --git a/src/reader/expect_formal_xs.cpp b/src/reader/expect_formal_xs.cpp
index 28e19ce4..3bb72dad 100644
--- a/src/reader/expect_formal_xs.cpp
+++ b/src/reader/expect_formal_xs.cpp
@@ -11,7 +11,7 @@
 #include "xo/expression/Variable.hpp"
 
 namespace xo {
-    using xo::ast::Variable;
+    using xo::scm::Variable;
     using xo::reflect::TypeDescr;
 
     namespace scm{
diff --git a/src/reader/exprseq_xs.cpp b/src/reader/exprseq_xs.cpp
index 77c5e696..f58f846d 100644
--- a/src/reader/exprseq_xs.cpp
+++ b/src/reader/exprseq_xs.cpp
@@ -123,7 +123,7 @@ namespace xo {
         exprseq_xs::on_bool_token(const token_type & tk,
                                   parserstatemachine * p_psm)
         {
-            using xo::ast::Constant;
+            using xo::scm::Constant;
 
             constexpr bool c_debug_flag = true;
             scope log(XO_DEBUG(c_debug_flag));
@@ -150,7 +150,7 @@ namespace xo {
         exprseq_xs::on_i64_token(const token_type & tk,
                                  parserstatemachine * p_psm)
         {
-            using xo::ast::Constant;
+            using xo::scm::Constant;
 
             scope log(XO_DEBUG(p_psm->debug_flag()));
 
@@ -176,7 +176,7 @@ namespace xo {
         exprseq_xs::on_f64_token(const token_type & tk,
                                  parserstatemachine * p_psm)
         {
-            using xo::ast::Constant;
+            using xo::scm::Constant;
 
             scope log(XO_DEBUG(p_psm->debug_flag()));
 
diff --git a/src/reader/exprstate.cpp b/src/reader/exprstate.cpp
index f7d25dcc..cbcc3560 100644
--- a/src/reader/exprstate.cpp
+++ b/src/reader/exprstate.cpp
@@ -18,7 +18,7 @@
 //#include "xo/reflect/Reflect.hpp"
 
 namespace xo {
-    //using xo::ast::Constant;
+    //using xo::scm::Constant;
     //using xo::reflect::Reflect;
     using xo::reflect::TypeDescr;
     using xo::print::ppindentinfo;
diff --git a/src/reader/lambda_xs.cpp b/src/reader/lambda_xs.cpp
index e1dfe722..c2a2ea0f 100644
--- a/src/reader/lambda_xs.cpp
+++ b/src/reader/lambda_xs.cpp
@@ -10,8 +10,8 @@
 #include "xo/expression/Lambda.hpp"
 
 namespace xo {
-    using xo::ast::Lambda;
-    using xo::ast::LocalEnv;
+    using xo::scm::Lambda;
+    using xo::scm::LocalEnv;
 
     namespace scm {
         const char *
diff --git a/src/reader/let1_xs.cpp b/src/reader/let1_xs.cpp
index 1a2c444e..619d677c 100644
--- a/src/reader/let1_xs.cpp
+++ b/src/reader/let1_xs.cpp
@@ -12,14 +12,14 @@
 #include "xo/expression/Lambda.hpp"
 
 namespace xo {
-    using Sequence = xo::ast::Sequence;
-    using DefineExpr = xo::ast::DefineExpr;
-    using Apply = xo::ast::Apply;
-    using Lambda = xo::ast::Lambda;
-    using LambdaAccess = xo::ast::LambdaAccess;
-    using Environment = xo::ast::Environment;
-    using LocalEnv = xo::ast::LocalEnv;
-    using Variable = xo::ast::Variable;
+    using Sequence = xo::scm::Sequence;
+    using DefineExpr = xo::scm::DefineExpr;
+    using Apply = xo::scm::Apply;
+    using Lambda = xo::scm::Lambda;
+    using LambdaAccess = xo::scm::LambdaAccess;
+    using Environment = xo::scm::Environment;
+    using LocalEnv = xo::scm::LocalEnv;
+    using Variable = xo::scm::Variable;
 
     namespace scm {
         std::unique_ptr<let1_xs>
diff --git a/src/reader/parser.cpp b/src/reader/parser.cpp
index fe55aa5f..e06eb4d0 100644
--- a/src/reader/parser.cpp
+++ b/src/reader/parser.cpp
@@ -17,8 +17,8 @@
 #include <stdexcept>
 
 namespace xo {
-    using xo::ast::Expression;
-    using xo::ast::LocalEnv;
+    using xo::scm::Expression;
+    using xo::scm::LocalEnv;
     using xo::reflect::TypeDescr;
 
     namespace scm {
diff --git a/src/reader/parserstatemachine.cpp b/src/reader/parserstatemachine.cpp
index 90c2d079..a7c97f79 100644
--- a/src/reader/parserstatemachine.cpp
+++ b/src/reader/parserstatemachine.cpp
@@ -11,8 +11,8 @@
 #include "xo/expression/pretty_expression.hpp"
 
 namespace xo {
-    using xo::ast::LocalEnv;
-    using xo::ast::Variable;
+    using xo::scm::LocalEnv;
+    using xo::scm::Variable;
 
     namespace scm {
         bp<Variable>
diff --git a/src/reader/progress_xs.cpp b/src/reader/progress_xs.cpp
index 2c94733a..e7047945 100644
--- a/src/reader/progress_xs.cpp
+++ b/src/reader/progress_xs.cpp
@@ -11,10 +11,10 @@
 #include "xo/expression/pretty_expression.hpp"
 
 namespace xo {
-    using xo::ast::Expression;
-    using xo::ast::AssignExpr;
-    using xo::ast::Variable;
-    using xo::ast::Apply;
+    using xo::scm::Expression;
+    using xo::scm::AssignExpr;
+    using xo::scm::Variable;
+    using xo::scm::Apply;
 
     namespace scm {
         const char *
diff --git a/src/reader/sequence_xs.cpp b/src/reader/sequence_xs.cpp
index 0d5b51ab..aa41c387 100644
--- a/src/reader/sequence_xs.cpp
+++ b/src/reader/sequence_xs.cpp
@@ -9,7 +9,7 @@
 #include "xo/expression/pretty_expression.hpp"
 
 namespace xo {
-    using xo::ast::DefineExpr;
+    using xo::scm::DefineExpr;
 
     namespace scm {
         std::unique_ptr<sequence_xs>
diff --git a/utest/parser.test.cpp b/utest/parser.test.cpp
index 18b52723..004b8497 100644
--- a/utest/parser.test.cpp
+++ b/utest/parser.test.cpp
@@ -16,7 +16,7 @@ namespace xo {
     using std::cerr;
     using std::endl;
 
-    //using xo::ast::Expression;
+    //using xo::scm::Expression;
 
     namespace ut {
         TEST_CASE("parser", "[parser]") {