diff --git a/include/utl/com/_1wire.h b/include/utl/com/_1wire.h
index 7dad5f9..55cb026 100644
--- a/include/utl/com/_1wire.h
+++ b/include/utl/com/_1wire.h
@@ -21,10 +21,10 @@
 #ifndef __utl_com_1wire_h__
 #define __utl_com_1wire_h__
 
-#include <utl/impl/impl.h>
-#include <utl/helper/crtp.h>
-#include <utl/meta/sfinae.h>
+#include <utl/core/impl.h>
+#include <utl/core/crtp.h>
 #include <utl/com/_1wire_id.h>
+#include <utl/meta/meta.h>
 
 
 namespace utl {
@@ -681,27 +681,27 @@ namespace _1wire_i_det {
 
       //! Primary template to catch any non 1-wire interface types
       template <typename _Tp, typename =void>
-      struct is_1wire_ : false_ {};
+      struct is_1wire_ : meta::false_ {};
 
       //! template to catch a proper 1-wire interface type
       template <typename _Tp>
       struct is_1wire_ <_Tp,
-         void_t <
+         meta::void_t <
 //            typename _Tp::Speed,
 //            typename _Tp::Command,
-            use_if_same_t <try_reset_t <_Tp>,    bool>,
-            use_if_same_t <try_rx1_t <_Tp>,      byte_t>,
-            //use_if_same_t <try_rx2_t <_Tp>,      size_t>,
-            use_if_same_t <try_tx1_t <_Tp>,      byte_t>,
-            //use_if_same_t <try_tx2_t <_Tp>,      size_t>,
-            use_if_same_t <try_match_t<_Tp>,        void>,
-            use_if_same_t <try_match_n_ovdr_t<_Tp>, void>,
-            use_if_same_t <try_skip_t<_Tp>,         void>,
-            use_if_same_t <try_skip_n_ovdr_t<_Tp>,  void>,
-            use_if_same_t <try_first_t <_Tp>,    _1wire_id_t>,
-            use_if_same_t <try_next_t <_Tp>,     _1wire_id_t>
+            meta::use_if_same_t <try_reset_t <_Tp>,    bool>,
+            meta::use_if_same_t <try_rx1_t <_Tp>,      byte_t>,
+            //meta::use_if_same_t <try_rx2_t <_Tp>,      size_t>,
+            meta::use_if_same_t <try_tx1_t <_Tp>,      byte_t>,
+            //meta::use_if_same_t <try_tx2_t <_Tp>,      size_t>,
+            meta::use_if_same_t <try_match_t<_Tp>,        void>,
+            meta::use_if_same_t <try_match_n_ovdr_t<_Tp>, void>,
+            meta::use_if_same_t <try_skip_t<_Tp>,         void>,
+            meta::use_if_same_t <try_skip_n_ovdr_t<_Tp>,  void>,
+            meta::use_if_same_t <try_first_t <_Tp>,    _1wire_id_t>,
+            meta::use_if_same_t <try_next_t <_Tp>,     _1wire_id_t>
          >  //!^ SFINAE may apply
-      > : true_ {};
+      > : meta::true_ {};
    } // namespace _1wire_i_det
 
    /*!
diff --git a/include/utl/com/_1wire_id.h b/include/utl/com/_1wire_id.h
index d3ca3d4..e655246 100644
--- a/include/utl/com/_1wire_id.h
+++ b/include/utl/com/_1wire_id.h
@@ -21,7 +21,7 @@
 #ifndef __utl_com_1wire_id_h__
 #define __utl_com_1wire_id_h__
 
-#include <utl/impl/impl.h>
+#include <utl/core/impl.h>
 #include <utl/container/id.h>
 
 namespace utl {
diff --git a/include/utl/com/_1wire_uart.h b/include/utl/com/_1wire_uart.h
index 18876ab..ec75d49 100644
--- a/include/utl/com/_1wire_uart.h
+++ b/include/utl/com/_1wire_uart.h
@@ -29,8 +29,8 @@
 #ifndef __utl_com_1wire_uart_h__
 #define __utl_com_1wire_uart_h__
 
-#include <utl/impl/impl.h>
-#include <utl/helper/crtp.h>
+#include <utl/core/impl.h>
+#include <utl/core/crtp.h>
 #include <utl/com/_1wire.h>
 
 namespace utl {
diff --git a/include/utl/com/i2c.h b/include/utl/com/i2c.h
index f04af8a..3d6b35e 100644
--- a/include/utl/com/i2c.h
+++ b/include/utl/com/i2c.h
@@ -21,9 +21,9 @@
 #ifndef _utl_com_i2c_h__
 #define _utl_com_i2c_h__
 
-#include <utl/impl/impl.h>
-#include <utl/helper/crtp.h>
-#include <utl/meta/sfinae.h>
+#include <utl/core/impl.h>
+#include <utl/core/crtp.h>
+#include <utl/meta/meta.h>
 
 namespace utl {
 
@@ -254,21 +254,21 @@ namespace utl {
 
       //! Primary template to catch any non I2C interface types
       template <typename _Tp, typename =void>
-      struct is_i2c_ : false_ { };
+      struct is_i2c_ : meta::false_ { };
 
       //! template to catch a proper I2C interface type
       template <typename _Tp>
       struct is_i2c_ <_Tp,
-         void_t <
+         meta::void_t <
             typename _Tp::Sequence,
-            use_if_same_t <uint32_t,try_cclk_t <_Tp>>,
-            use_if_same_t <void,    try_clk_t <_Tp>>,
-            use_if_same_t <void,    try_start_t <_Tp>>,
-            use_if_same_t <void,    try_stop_t <_Tp>>,
-            use_if_same_t <byte_t,  try_rx_data_t <_Tp>>,
-            use_if_same_t <bool,    try_tx_data_t <_Tp>>
+            meta::use_if_same_t <uint32_t,try_cclk_t <_Tp>>,
+            meta::use_if_same_t <void,    try_clk_t <_Tp>>,
+            meta::use_if_same_t <void,    try_start_t <_Tp>>,
+            meta::use_if_same_t <void,    try_stop_t <_Tp>>,
+            meta::use_if_same_t <byte_t,  try_rx_data_t <_Tp>>,
+            meta::use_if_same_t <bool,    try_tx_data_t <_Tp>>
          >
-      > : true_ { };
+      > : meta::true_ { };
    }
    /*!
     * Value meta-programming function alias for I2C interface checking
diff --git a/include/utl/com/i2c_bb.h b/include/utl/com/i2c_bb.h
index a832c25..9110b46 100644
--- a/include/utl/com/i2c_bb.h
+++ b/include/utl/com/i2c_bb.h
@@ -22,8 +22,8 @@
 #ifndef __utl_com_i2c_bb_h__
 #define __utl_com_i2c_bb_h__
 
-#include <utl/impl/impl.h>
-#include <utl/helper/crtp.h>
+#include <utl/core/impl.h>
+#include <utl/core/crtp.h>
 #include <utl/com/i2c.h>
 
 
diff --git a/include/utl/com/spi.h b/include/utl/com/spi.h
index 43d87ea..72dfc04 100644
--- a/include/utl/com/spi.h
+++ b/include/utl/com/spi.h
@@ -21,9 +21,9 @@
 #ifndef _utl_com_spi_h__
 #define _utl_com_spi_h__
 
-#include <utl/impl/impl.h>
-#include <utl/helper/crtp.h>
-#include <utl/meta/sfinae.h>
+#include <utl/core/impl.h>
+#include <utl/core/crtp.h>
+#include <utl/meta/meta.h>
 
 namespace utl {
 
@@ -302,19 +302,19 @@ namespace utl {
 
       //! Primary template to catch any non SPI interface types
       template <typename _Tp, typename =void>
-      struct is_spi_ : false_ {};
+      struct is_spi_ : meta::false_ {};
 
       //! template to catch a proper SPI interface type
       template <typename _Tp>
       struct is_spi_ <
          _Tp,
-         void_t <
-            use_if_same_t <try_cclock_t<_Tp>, uint32_t>,
-            use_if_same_t <try_clock_t<_Tp>,  void>,
-            use_if_same_t <try_tx_t<_Tp>,     byte_t>,
-            use_if_same_t <try_rx_t<_Tp>,     byte_t>
+         meta::void_t <
+            meta::use_if_same_t <try_cclock_t<_Tp>, uint32_t>,
+            meta::use_if_same_t <try_clock_t<_Tp>,  void>,
+            meta::use_if_same_t <try_tx_t<_Tp>,     byte_t>,
+            meta::use_if_same_t <try_rx_t<_Tp>,     byte_t>
          >
-      > : true_ {};
+      > : meta::true_ {};
    }
    /*!
     * Value meta-programming function for SPI interface checking
diff --git a/include/utl/com/spi_bb.h b/include/utl/com/spi_bb.h
index 90f5878..45bacce 100644
--- a/include/utl/com/spi_bb.h
+++ b/include/utl/com/spi_bb.h
@@ -22,10 +22,10 @@
 #ifndef __utl_com_spi_bb_h__
 #define __utl_com_spi_bb_h__
 
-#include <utl/impl/impl.h>
-#include <utl/helper/crtp.h>
-#include <utl/meta/sfinae.h>
+#include <utl/core/impl.h>
+#include <utl/core/crtp.h>
 #include <utl/com/spi.h>
+#include <utl/meta/meta.h>
 
 
 namespace utl {
@@ -75,9 +75,9 @@ namespace utl {
    //! \name SPI implementation specific functions
    //!@{
       template <spi::bitOrder B =BitOrder> constexpr
-         use_if_t <(B == spi::bitOrder::LSB_First), void> shift (byte_t& b) { b <<=1; }
+      meta::use_if_t <(B == spi::bitOrder::LSB_First), void> shift (byte_t& b) { b <<=1; }
       template <spi::bitOrder B =BitOrder> constexpr
-         use_if_t <(B == spi::bitOrder::MSB_First), void> shift (byte_t& b) { b >>=1; }
+      meta::use_if_t <(B == spi::bitOrder::MSB_First), void> shift (byte_t& b) { b >>=1; }
       template <spi::cpol C =CPOL> static constexpr bool clkHigh () {
          return !static_cast<bool>(C);
       }
@@ -113,9 +113,9 @@ namespace utl {
       byte_t _tx_data (byte_t out) { return _tx_data_impl (out); }
 
       template <spi::cpha C =CPHA>
-      use_if_t <(C == spi::cpha::LOW), byte_t> _tx_data_impl (byte_t out);
+      meta::use_if_t <(C == spi::cpha::LOW), byte_t> _tx_data_impl (byte_t out);
       template <spi::cpha C =CPHA>
-      use_if_t <(C == spi::cpha::HIGH), byte_t> _tx_data_impl (byte_t out);
+      meta::use_if_t <(C == spi::cpha::HIGH), byte_t> _tx_data_impl (byte_t out);
    //!@}
 
    //! Data members
@@ -134,7 +134,7 @@ namespace utl {
     */
    template <typename impl_t, spi::cpol CPOL, spi::cpha CPHA, spi::bitOrder BitOrder>
    template <spi::cpha C>
-      use_if_t <(C == spi::cpha::LOW), byte_t>
+      meta::use_if_t <(C == spi::cpha::LOW), byte_t>
       spi_bb_i<impl_t, CPOL, CPHA, BitOrder>::_tx_data_impl (byte_t out) {
          byte_t in {};
          SCLK (clkL_);
@@ -158,7 +158,7 @@ namespace utl {
     */
    template <typename impl_t, spi::cpol CPOL, spi::cpha CPHA, spi::bitOrder BitOrder>
    template <spi::cpha C>
-      use_if_t <(C == spi::cpha::HIGH), byte_t>
+      meta::use_if_t <(C == spi::cpha::HIGH), byte_t>
       spi_bb_i<impl_t, CPOL, CPHA, BitOrder>::_tx_data_impl (byte_t out) {
          byte_t in {};
          SCLK (clkL_);
@@ -207,9 +207,9 @@ namespace utl {
    //! \name SPI implementation specific functions
    //!@{
       template <spi::bitOrder B =BitOrder> constexpr
-         use_if_t <(B == spi::bitOrder::LSB_First), void> shift (byte_t& b) { b <<=1; }
+      meta::use_if_t <(B == spi::bitOrder::LSB_First), void> shift (byte_t& b) { b <<=1; }
       template <spi::bitOrder B =BitOrder> constexpr
-         use_if_t <(B == spi::bitOrder::MSB_First), void> shift (byte_t& b) { b >>=1; }
+      meta::use_if_t <(B == spi::bitOrder::MSB_First), void> shift (byte_t& b) { b >>=1; }
       template <spi::cpol C =CPOL> static constexpr bool clkHigh () {
          return !static_cast<bool>(C);
       }
@@ -241,9 +241,9 @@ namespace utl {
       byte_t _tx_data (byte_t out) final { return _tx_data_impl (out); }
 
       template <spi::cpha C =CPHA>
-      use_if_t <(C == spi::cpha::LOW), byte_t> _tx_data_impl (byte_t out);
+      meta::use_if_t <(C == spi::cpha::LOW), byte_t> _tx_data_impl (byte_t out);
       template <spi::cpha C =CPHA>
-      use_if_t <(C == spi::cpha::HIGH), byte_t> _tx_data_impl (byte_t out);
+      meta::use_if_t <(C == spi::cpha::HIGH), byte_t> _tx_data_impl (byte_t out);
    //!@}
 
    //! Data members
@@ -262,7 +262,7 @@ namespace utl {
     */
    template <spi::cpol CPOL, spi::cpha CPHA, spi::bitOrder BitOrder>
    template <spi::cpha C>
-      use_if_t <(C == spi::cpha::LOW), byte_t>
+      meta::use_if_t <(C == spi::cpha::LOW), byte_t>
       spi_bb_i<virtual_tag, CPOL, CPHA, BitOrder>::_tx_data_impl (byte_t out) {
          byte_t in {};
          SCLK (clkL_);
@@ -286,7 +286,7 @@ namespace utl {
     */
    template <spi::cpol CPOL, spi::cpha CPHA, spi::bitOrder BitOrder>
    template <spi::cpha C>
-      use_if_t <(C == spi::cpha::HIGH), byte_t>
+      meta::use_if_t <(C == spi::cpha::HIGH), byte_t>
       spi_bb_i<virtual_tag, CPOL, CPHA, BitOrder>::_tx_data_impl (byte_t out) {
          byte_t in {};
          SCLK (clkL_);
diff --git a/include/utl/container/array.h b/include/utl/container/array.h
index 55513b5..6987d05 100644
--- a/include/utl/container/array.h
+++ b/include/utl/container/array.h
@@ -21,7 +21,7 @@
 #ifndef __utl_container_array_h__
 #define __utl_container_array_h__
 
-#include <utl/impl/impl.h>
+#include <utl/core/impl.h>
 #include <algorithm>
 
 namespace utl {
diff --git a/include/utl/container/id.h b/include/utl/container/id.h
index cd40256..2496425 100644
--- a/include/utl/container/id.h
+++ b/include/utl/container/id.h
@@ -22,7 +22,7 @@
 #ifndef __utl_container_id_h__
 #define __utl_container_id_h__
 
-#include <utl/impl/impl.h>
+#include <utl/core/impl.h>
 #include <utl/container/array.h>
 #include <algorithm>
 
diff --git a/include/utl/core/crtp.h b/include/utl/core/crtp.h
index fde5d77..e67cfad 100644
--- a/include/utl/core/crtp.h
+++ b/include/utl/core/crtp.h
@@ -21,7 +21,7 @@
 #ifndef __utl_impl_crtp_h__
 #define __utl_impl_crtp_h__
 
-#include <utl/impl/impl.h>
+#include <utl/core/impl.h>
 
 /*!
  * \defgroup crtp   CRTP idiom support header
diff --git a/include/utl/core/impl.h b/include/utl/core/impl.h
index 8346a52..7715154 100644
--- a/include/utl/core/impl.h
+++ b/include/utl/core/impl.h
@@ -1,6 +1,6 @@
 /*!
- * \file   /utl/impl/impl.h
- * \brief  Implementation detail main header
+ * \file   /utl/core/impl.h
+ * \brief  Implementation detail main forward header
  *
  * Copyright (C) 2018 Christos Choutouridis
  *
@@ -18,17 +18,13 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  *
  */
-#ifndef __utl_impl_impl_h__
-#define __utl_impl_impl_h__
+#ifndef __utl_core_impl_h__
+#define __utl_core_impl_h__
 
 
-// Include implementation details once
-#include <utl/impl/version.h>
-#include <utl/impl/concepts.h>
-#include <utl/impl/types.h>
+// FWD include implementation details once
+#include <utl/core/version.h>
+#include <utl/core/types.h>
 
-// STL dependency
-#include <type_traits>
 
-
-#endif /* __utl_impl_impl_h__ */
+#endif /* __utl_core_impl_h__ */
diff --git a/include/utl/core/types.h b/include/utl/core/types.h
index 8f614ba..909fc90 100644
--- a/include/utl/core/types.h
+++ b/include/utl/core/types.h
@@ -1,5 +1,5 @@
 /*!
- * \file   /utl/impl/types.h
+ * \file   /utl/core/types.h
  * \brief  Basic type alias support
  *
  * Copyright (C) 2018 Christos Choutouridis
@@ -18,15 +18,25 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  *
  */
-#ifndef __utl_impl_types_h__
-#define __utl_impl_types_h__
+#ifndef __utl_core_types_h__
+#define __utl_core_types_h__
 
-#include <stdint.h>
+#include <cstddef>
+#include <cstdint>
 
+namespace utl {
+   //! @{ \name byte and word types
+   using byte_t   = uint8_t;     //!< 8 bits wide
+   using word_t   = uint16_t;    //!< 16 bits wide
+   using dword_t  = uint32_t;    //!< 32 bits wide
+   //! @}
 
-typedef uint8_t  byte_t;         /*!< 8 bits wide */
-typedef uint16_t word_t;         /*!< 16 bits wide */
-typedef uint32_t dword_t;        /*!< 32 bits wide */
+   //! @{ \name size and index
+   using size_t   = std::size_t;
+   using index_t  = size_t;      //!< index_t and size_t mend to be interchangeable
 
+   using ptrdiff_t= std::ptrdiff_t;
+   //! @}
+}
 
-#endif /* __utl_impl_types_h__ */
+#endif /* __utl_core_types_h__ */
diff --git a/include/utl/core/version.h b/include/utl/core/version.h
index 49c52fc..cdfc488 100755
--- a/include/utl/core/version.h
+++ b/include/utl/core/version.h
@@ -1,6 +1,6 @@
 /*!
- * \file   /utl/impl/version.h
- * \brief  version and cpp version check
+ * \file   /utl/core/version.h
+ * \brief  version and cpp version checks
  *
  * Copyright (C) 2018 Christos Choutouridis
  *
@@ -18,23 +18,88 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  *
  */
-#ifndef __utl_impl_version_h__
-#define __utl_impl_version_h__
+#ifndef __utl_core_version_h__
+#define __utl_core_version_h__
 
 //!\defgroup version version
 //! Definitions of the utl version
-//!\ingroup impl
+//!@{
 
-#define UTL_VERSION       "0.0.0"
+//! utl version
+#define UTL_VERSION       "0.0.1"
 #define UTL_VERSION_MAJOR  0
 #define UTL_VERSION_MINOR  0
-#define UTL_VERSION_PATCH  0
+#define UTL_VERSION_PATCH  1
 #define UTL_VERSION_VALUE ( (UTL_VERSION_MAJOR * 10000) \
                           + (UTL_VERSION_MINOR * 100)   \
                           + UTL_VERSION_PATCH)
 
-#if __cplusplus < 201103L
+//! C++ versions
+#define CXX_VER            __cplusplus
+#define CXX_VER_STD_11     201103L
+#define CXX_VER_STD_14     201402L
+#define CXX_VER_STD_17     201703L
+
+//#include <type_traits>
+
+//! Check for variable templates
+#ifndef CXX_VARIABLE_TEMPLATES
+ #ifdef  __cpp_variable_templates
+  #define CXX_VARIABLE_TEMPLATES __cpp_variable_templates
+ #else
+  #define CXX_VARIABLE_TEMPLATES (CXX_VER >= CXX_VER_STD_14)
+ #endif
+#endif
+
+//! Check integer sequence
+#ifndef CXX_INTEGER_SEQUENCE
+ #ifdef __cpp_lib_integer_sequence
+  #define CXX_INTEGER_SEQUENCE __cpp_lib_integer_sequence
+ #else
+  #define CXX_INTEGER_SEQUENCE (CXX_VER >= CXX_VER_STD_14)
+ #endif
+#endif
+
+//! Check concepts
+#ifndef CXX_CONCEPTS
+ #ifdef __cpp_concepts
+  #define CXX_CONCEPTS __cpp_concepts
+ #else
+  #define CXX_CONCEPTS 0
+ #endif
+#endif
+
+//! Check for inline variables
+#ifndef CXX_INLINE_VARIABLES
+ #ifdef __cpp_inline_variables
+  #define CXX_INLINE_VARIABLES __cpp_inline_variables
+ #else
+  #define CXX_INLINE_VARIABLES (CXX_VER >= CXX_VER_STD_17)
+ #endif
+#endif
+
+#ifndef CXX_FOLD_EXPRESSIONS
+ #ifdef __cpp_fold_expressions
+  #define CXX_FOLD_EXPRESSIONS __cpp_fold_expressions
+ #else
+  #define CXX_FOLD_EXPRESSIONS (CXX_VER >= CXX_VER_STD_17)
+ #endif
+#endif
+
+
+/*
+ * Workaround inspection
+ */
+#if defined(__GNUC__) && (__GNUC__ < 5)
+ // https://wg21.link/cwg1558
+ #define UTL_WORKAROUND_CWG_1558
+#endif
+
+
+//! Base library requirement
+#if __cplusplus < CXX_VER_STD_11
 #error "uTL requires C++11"
 #endif
 
-#endif /* __utl_impl_version_h__ */
+//!@}
+#endif /* #ifndef __utl_core_version_h__ */
diff --git a/include/utl/dev/dev_iterators.h b/include/utl/dev/dev_iterators.h
index bda07b3..e417730 100644
--- a/include/utl/dev/dev_iterators.h
+++ b/include/utl/dev/dev_iterators.h
@@ -278,23 +278,23 @@ namespace utl {
 
          //! Primary template to catch any non SPI interface types
          template <typename _Tp, typename =void>
-         struct is_outdev_it_ : false_ {};
+         struct is_outdev_it_ : meta::false_ {};
 
          //! template to catch a proper SPI interface type
          template <typename _Tp>
          struct is_outdev_it_ <
             _Tp,
-            void_t <
-               typename T::value_type,
-               typename T::difference_type,
-               typename T::pointer,
-               typename T::reference,
-               use_if_same_t <
-                  typename T::iterator_category,
+            meta::void_t <
+               typename _Tp::value_type,
+               typename _Tp::difference_type,
+               typename _Tp::pointer,
+               typename _Tp::reference,
+               meta::use_if_same_t <
+                  typename _Tp::iterator_category,
                   std::output_iterator_tag
                >
             >
-         > : true_ {};
+         > : meta::true_ {};
       }
       /*!
        * Value meta-programming function for SPI interface checking
@@ -525,23 +525,23 @@ namespace utl {
 
          //! Primary template to catch any non SPI interface types
          template <typename _Tp, typename =void>
-         struct is_indev_it_ : false_ {};
+         struct is_indev_it_ : meta::false_ {};
 
          //! template to catch a proper SPI interface type
          template <typename _Tp>
          struct is_indev_it_ <
             _Tp,
-            void_t <
-               typename T::value_type,
-               typename T::difference_type,
-               typename T::pointer,
-               typename T::reference,
-               use_if_same_t <
-                  typename T::iterator_category,
+            meta::void_t <
+               typename _Tp::value_type,
+               typename _Tp::difference_type,
+               typename _Tp::pointer,
+               typename _Tp::reference,
+               meta::use_if_same_t <
+                  typename _Tp::iterator_category,
                   std::input_iterator_tag
                >
             >
-         > : true_ {};
+         > : meta::true_ {};
       }
       /*!
        * Value meta-programming function for SPI interface checking
@@ -821,23 +821,23 @@ namespace utl {
 
          //! Primary template to catch any non SPI interface types
          template <typename _Tp, typename =void>
-         struct is_idxdev_it_ : false_ {};
+         struct is_idxdev_it_ : meta::false_ {};
 
          //! template to catch a proper SPI interface type
          template <typename _Tp>
          struct is_idxdev_it_ <
             _Tp,
-            void_t <
-               typename T::value_type,
-               typename T::difference_type,
-               typename T::pointer,
-               typename T::reference,
-               use_if_same_t <
-                  typename T::iterator_category,
+            meta::void_t <
+               typename _Tp::value_type,
+               typename _Tp::difference_type,
+               typename _Tp::pointer,
+               typename _Tp::reference,
+               meta::use_if_same_t <
+                  typename _Tp::iterator_category,
                   std::input_iterator_tag
                >
             >
-         > : true_ {};
+         > : meta::true_ {};
       }
       /*!
        * Value meta-programming function for SPI interface checking
diff --git a/include/utl/dev/idx_dev.h b/include/utl/dev/idx_dev.h
index 4e719e1..6a27c12 100644
--- a/include/utl/dev/idx_dev.h
+++ b/include/utl/dev/idx_dev.h
@@ -22,10 +22,10 @@
 #ifndef __utl_dev_idx_dev_h__
 #define __utl_dev_idx_dev_h__
 
-#include <utl/impl/impl.h>
-#include <utl/helper/crtp.h>
-#include <utl/meta/sfinae.h>
+#include <utl/core/impl.h>
+#include <utl/core/crtp.h>
 #include <utl/dev/dev_iterators.h>
+#include <utl/meta/meta.h>
 
 namespace utl {
 
diff --git a/include/utl/dev/in_dev.h b/include/utl/dev/in_dev.h
index 4cd7a47..8e615d7 100644
--- a/include/utl/dev/in_dev.h
+++ b/include/utl/dev/in_dev.h
@@ -21,10 +21,10 @@
 #ifndef __utl_dev_in_dev_h__
 #define __utl_dev_in_dev_h__
 
-#include <utl/impl/impl.h>
-#include <utl/helper/crtp.h>
-#include <utl/meta/sfinae.h>
+#include <utl/core/impl.h>
+#include <utl/core/crtp.h>
 #include <utl/dev/dev_iterators.h>
+#include <utl/meta/meta.h>
 
 namespace utl {
 
diff --git a/include/utl/dev/inbuf_dev.h b/include/utl/dev/inbuf_dev.h
index db4f36a..dd45dcf 100644
--- a/include/utl/dev/inbuf_dev.h
+++ b/include/utl/dev/inbuf_dev.h
@@ -22,10 +22,10 @@
 #ifndef __utl_dev_inbuf_dev_h__
 #define __utl_dev_inbuf_dev_h__
 
-#include <utl/impl/impl.h>
-#include <utl/helper/crtp.h>
-#include <utl/meta/sfinae.h>
+#include <utl/core/impl.h>
+#include <utl/core/crtp.h>
 #include <utl/dev/dev_iterators.h>
+#include <utl/meta/meta.h>
 
 namespace utl {
 
diff --git a/include/utl/meta/bool.h b/include/utl/meta/bool.h
deleted file mode 100644
index 5e91e00..0000000
--- a/include/utl/meta/bool.h
+++ /dev/null
@@ -1,48 +0,0 @@
-/*!
- * \file    bool.h
- * \brief   Template meta-programming bool integral constant
- *
- * Copyright (C) 2018 Christos Choutouridis
- *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU Lesser General Public License as
- * published by the Free Software Foundation, either version 3
- * of the License, or (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
- */
-#ifndef __utl_meta_bool_h__
-#define __utl_meta_bool_h__
-
-#include <utl/impl/impl.h>
-#include <utl/meta/integral.h>
-
-/*!
- * \ingroup meta
- * \defgroup bool
- * boolean constant type support header
- */
-//! @{
-
-namespace utl {
-
-   //! bool_ type
-   template<bool _v>
-     using bool_ = integral_<bool, _v>;
-
-   //! The type used as a compile-time boolean with true value.
-   typedef bool_<true>  true_;
-
-   //! The type used as a compile-time boolean with false value.
-   typedef bool_<false> false_;
-
-}
-
-//! @}
-#endif /* __utl_meta_bool_h__ */
diff --git a/include/utl/meta/detect.h b/include/utl/meta/detect.h
deleted file mode 100644
index 49964a4..0000000
--- a/include/utl/meta/detect.h
+++ /dev/null
@@ -1,70 +0,0 @@
-/*!
- * \file    utl/meta/detect.h
- * \brief   Template meta-programming void helpers
- *
- * Copyright (C) 2018 Christos Choutouridis
- *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU Lesser General Public License as
- * published by the Free Software Foundation, either version 3
- * of the License, or (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
- */
-#ifndef __utl_meta_detect_h__
-#define __utl_meta_detect_h__
-
-#include <utl/impl/impl.h>
-#include <utl/meta/sfinae.h>
-
-/*!
- * \ingroup meta
- * \defgroup detect
- * Implementation of the detection idiom
- */
-//! @{
-
-namespace utl {
-
-   //! detection idiom (negative case).
-   template <typename _Def,
-             typename _AlwaysVoid,
-             template<typename...> class _Op,
-             typename... _Args>
-   struct detector_ {
-      using value_ = false_;
-      using type = _Def;
-   };
-
-   //! detection idiom (positive case).
-   template <typename _Def,
-             template<typename...> class _Op,
-             typename... _Args>
-   struct detector_ <_Def, void_t<_Op<_Args...>>, _Op, _Args...> {
-      using value_ = true_;
-      using type = _Op<_Args...>;
-   };
-
-   // Detect whether _Op<_Args...> is a valid type, use _Def if not.
-   template <typename _Def,
-             template<typename...> class _Op,
-             typename... _Args>
-   using detected_or_ = detector_ <_Def, void, _Op, _Args...>;
-
-   // template alias
-   template <typename _Def,
-             template<typename...> class _Op,
-             typename... _Args>
-   using detected_or_t = typename detected_or_<_Def, _Op, _Args...>::type;
-
-
-
-}
-//! @}
-#endif /* __utl_meta_detect_h__ */
diff --git a/include/utl/meta/if.h b/include/utl/meta/if.h
deleted file mode 100644
index a82a878..0000000
--- a/include/utl/meta/if.h
+++ /dev/null
@@ -1,59 +0,0 @@
-/*!
- * \file    if.h
- * \brief   Template meta-programming conditional helpers
- *
- * Copyright (C) 2018 Christos Choutouridis
- *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU Lesser General Public License as
- * published by the Free Software Foundation, either version 3
- * of the License, or (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
- */
-#ifndef __utl_meta_if_h__
-#define __utl_meta_if_h__
-
-#include <utl/impl/impl.h>
-
-
-/*!
- * \ingroup meta
- * \defgroup if
- * conditional type support header
- */
-//! @{
-namespace utl {
-
-   //! select _T1 or _T2 based on _Sel
-   //! @{
-   template <bool _Sel, typename _T1, typename _T2>
-   struct select_ {
-      typedef _T1 type;
-   };
-
-   template <typename _T1, typename _T2>
-   struct select_ <false, _T1, _T2> {
-      typedef _T2 type;
-   };
-   //! @}
-
-   //! select _Tp if _Check is true, else SFINAE
-   //! @{
-   template <bool _Check, typename _Tp = void>
-   struct if_ {
-      typedef _Tp type;
-   };
-   template<typename _Tp>  // Partial specialization for false.
-   struct if_ <false, _Tp> { };
-
-}
-
-//! @}
-#endif /* __utl_meta_if_h__ */
diff --git a/include/utl/meta/invoke.h b/include/utl/meta/invoke.h
deleted file mode 100644
index 2211b47..0000000
--- a/include/utl/meta/invoke.h
+++ /dev/null
@@ -1,63 +0,0 @@
-/*!
- * \file    void.h
- * \brief   Template meta-programming void helpers
- *
- * Copyright (C) 2018 Christos Choutouridis
- *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU Lesser General Public License as
- * published by the Free Software Foundation, either version 3
- * of the License, or (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
- */
-#ifndef __utl_meta_void_h__
-#define __utl_meta_void_h__
-
-#include <utl/impl/impl.h>
-#include <utl/meta/bool.h>
-
-/*! \ingroup meta
- * \defgroup void
- * void_ support header
- */
-//! @{
-
-namespace utl {
-
-   /*!
-    * Like boost::mpl we made void_ a complete type to allow it to be
-    * instantiated so that it can be passed in as an object that can be
-    * used to select an overloaded function.
-    */
-   struct void_ {
-      typedef void_ type;
-   };
-
-   template<typename _Tp>
-   struct is_void_
-         : false_ { };
-
-   template<>
-   struct is_void_ <void_>
-      : true_ { };
-
-   template<typename _Tp>
-   struct is_not_void_
-      : true_ { };
-
-   template<>
-   struct is_not_void_<void_>
-      : false_ { };
-
-}
-
-//!@}
-
-#endif /* __utl_meta_void_h__ */
diff --git a/test/main.cpp b/test/main.cpp
index 7bf991a..925e7e0 100644
--- a/test/main.cpp
+++ b/test/main.cpp
@@ -18,12 +18,10 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  *
  */
-#include <gtest.h>
-#include <iostream>
+#include <gtest/gtest.h>
 
 
 GTEST_API_ int main(int argc, char **argv) {
-  std::cout << "Running tests from main.cpp\n";
   testing::InitGoogleTest(&argc, argv);
   return RUN_ALL_TESTS();
 }
diff --git a/test/tests/test_1w_impl.cpp b/test/tests/test_1w_impl.cpp
index eae2c9b..8412da9 100644
--- a/test/tests/test_1w_impl.cpp
+++ b/test/tests/test_1w_impl.cpp
@@ -17,7 +17,7 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  *
  */
-#include <gtest.h>
+#include <gtest/gtest.h>
 #include <utl/com/_1wire_uart.h>
 
 /*!
diff --git a/test/tests/test_i2c_impl.cpp b/test/tests/test_i2c_impl.cpp
index 3fd1d12..4dbd2e5 100644
--- a/test/tests/test_i2c_impl.cpp
+++ b/test/tests/test_i2c_impl.cpp
@@ -17,7 +17,7 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  *
  */
-#include <gtest.h>
+#include <gtest/gtest.h>
 #include <utl/com/i2c_bb.h>
 
 /*!
diff --git a/test/tests/test_spi_impl.cpp b/test/tests/test_spi_impl.cpp
index 212920f..ec14d56 100644
--- a/test/tests/test_spi_impl.cpp
+++ b/test/tests/test_spi_impl.cpp
@@ -17,9 +17,10 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  *
  */
-#include <gtest.h>
+#include <gtest/gtest.h>
 #include <utl/com/spi_bb.h>
 
+
 /*!
  * \warning
  *    This is not right way of testing communication interfaces. We have to