diff -Naur /old/boost/numeric/ublas/operation/size.hpp /new/boost/numeric/ublas/operation/size.hpp
--- /old/boost/numeric/ublas/operation/size.hpp	2010-07-02 16:01:55.000000000 +0200
+++ /new/boost/numeric/ublas/operation/size.hpp	2010-09-20 22:58:09.000000000 +0200
@@ -1,11 +1,9 @@
 /**
- * -*- c++ -*-
- *
  * \file size.hpp
  *
- * \brief The \c size operation.
+ * \brief The family of \c size operations.
  *
- * Copyright (c) 2009, Marco Guazzone
+ * Copyright (c) 2009-2010, Marco Guazzone
  *
  * Distributed under the Boost Software License, Version 1.0. (See
  * accompanying file LICENSE_1_0.txt or copy at
@@ -18,254 +16,333 @@
 #define BOOST_NUMERIC_UBLAS_OPERATION_SIZE_HPP
 
 
+#include <boost/mpl/has_xxx.hpp> 
+#include <boost/mpl/if.hpp>
 #include <boost/numeric/ublas/detail/config.hpp>
 #include <boost/numeric/ublas/expression_types.hpp>
 #include <boost/numeric/ublas/fwd.hpp>
 #include <boost/numeric/ublas/tags.hpp>
+#include <boost/numeric/ublas/traits.hpp>
+#include <boost/utility/enable_if.hpp>
 #include <cstddef>
 
 
 namespace boost { namespace numeric { namespace ublas {
 
-    namespace detail {
+namespace detail { namespace /*<unnamed>*/ {
+
+/// Define a \c has_size_type trait class.
+BOOST_MPL_HAS_XXX_TRAIT_DEF(size_type)
+
+
+/**
+ * \brief Wrapper type-traits used in \c boost::lazy_enabled_if for getting the
+ *  size type (see below).
+ * \tparam VectorT A vector type.
+ */
+template <typename VectorT>
+struct vector_size_type
+{
+    /// The size type.
+    typedef typename vector_traits<VectorT>::size_type type;
+};
+
+/**
+ * \brief Wrapper type-traits used in \c boost::lazy_enabled_if for getting the
+ *  size type (see below).
+ * \tparam MatrixT A matrix type.
+ */
+template <typename MatrixT>
+struct matrix_size_type
+{
+    /// The size type.
+    typedef typename matrix_traits<MatrixT>::size_type type;
+};
+
+
+/**
+ * \brief Auxiliary class for computing the size of the given dimension for
+ *  a container of the given category.
+ * \tparam Dim The dimension number (starting from 1).
+ * \tparam CategoryT The category type (e.g., vector_tag).
+ */
+template <std::size_t Dim, typename CategoryT>
+struct size_by_dim_impl;
+
+
+/**
+ * \brief Auxiliary class for computing the size of the given dimension for
+ *  a container of the given category and with the given orientation.
+ * \tparam Dim The dimension number (starting from 1).
+ * \tparam CategoryT The category type (e.g., vector_tag).
+ * \tparam OrientationT The orientation category type (e.g., row_major_tag).
+ */
+template <typename TagT, typename CategoryT, typename OrientationT>
+struct size_by_tag_impl;
+
+
+/**
+ * \brief Specialization of \c size_by_dim_impl for computing the size of a
+ *  vector.
+ */
+template <>
+struct size_by_dim_impl<1, vector_tag>
+{
+    /**
+     * \brief Compute the size of the given vector.
+     * \tparam ExprT A vector expression type.
+     * \pre ExprT must be a model of VectorExpression.
+     */
+    template <typename ExprT>
+    BOOST_UBLAS_INLINE
+    static typename vector_traits<ExprT>::size_type apply(vector_expression<ExprT> const& ve)
+    {
+        return ve().size();
+    }
+};
+
+
+/**
+ * \brief Specialization of \c size_by_dim_impl for computing the number of
+ *  rows of a matrix
+ */
+template <>
+struct size_by_dim_impl<1, matrix_tag>
+{
+    /**
+     * \brief Compute the number of rows of the given matrix.
+     * \tparam ExprT A matrix expression type.
+     * \pre ExprT must be a model of MatrixExpression.
+     */
+    template <typename ExprT>
+    BOOST_UBLAS_INLINE
+    static typename matrix_traits<ExprT>::size_type apply(matrix_expression<ExprT> const& me)
+    {
+        return me().size1();
+    }
+};
+
+
+/**
+ * \brief Specialization of \c size_by_dim_impl for computing the number of
+ *  columns of a matrix
+ */
+template <>
+struct size_by_dim_impl<2, matrix_tag>
+{
+    /**
+     * \brief Compute the number of columns of the given matrix.
+     * \tparam ExprT A matrix expression type.
+     * \pre ExprT must be a model of MatrixExpression.
+     */
+    template <typename ExprT>
+    BOOST_UBLAS_INLINE
+    static typename matrix_traits<ExprT>::size_type apply(matrix_expression<ExprT> const& me)
+    {
+        return me().size2();
+    }
+};
+
+
+/**
+ * \brief Specialization of \c size_by_tag_impl for computing the size of the
+ *  major dimension of a row-major oriented matrix.
+ */
+template <>
+struct size_by_tag_impl<tag::major, matrix_tag, row_major_tag>
+{
+    /**
+     * \brief Compute the number of rows of the given matrix.
+     * \tparam ExprT A matrix expression type.
+     * \pre ExprT must be a model of MatrixExpression.
+     */
+    template <typename ExprT>
+    BOOST_UBLAS_INLINE
+    static typename matrix_traits<ExprT>::size_type apply(matrix_expression<ExprT> const& me)
+    {
+        return me().size1();
+    }
+};
+
+
+/**
+ * \brief Specialization of \c size_by_tag_impl for computing the size of the
+ *  minor dimension of a row-major oriented matrix.
+ */
+template <>
+struct size_by_tag_impl<tag::minor, matrix_tag, row_major_tag>
+{
+    /**
+     * \brief Compute the number of columns of the given matrix.
+     * \tparam ExprT A matrix expression type.
+     * \pre ExprT must be a model of MatrixExpression.
+     */
+    template <typename ExprT>
+    BOOST_UBLAS_INLINE
+    static typename matrix_traits<ExprT>::size_type apply(matrix_expression<ExprT> const& me)
+    {
+        return me().size2();
+    }
+};
 
-        /**
-         * \brief Auxiliary class for computing the size of the given dimension for
-         *  a container of the given category..
-         * \tparam Dim The dimension number (starting from 1).
-         * \tparam CategoryT The category type (e.g., vector_tag).
-         */
-        template <size_t Dim, typename CategoryT>
-        struct size_by_dim_impl;
-
-
-        /// \brief Specialization of \c size_by_dim_impl for computing the size of a
-        ///  vector
-        template <>
-        struct size_by_dim_impl<1, vector_tag>
-        {
-            /**
-             * \brief Compute the size of the given vector.
-             * \tparam ExprT A vector expression type.
-             * \pre ExprT must be a model of VectorExpression.
-             */
-            template <typename ExprT>
-            BOOST_UBLAS_INLINE
-            static typename ExprT::size_type apply(ExprT const& e)
-            {
-                return e.size();
-            }
-        };
-
-
-        /// \brief Specialization of \c size_by_dim_impl for computing the number of
-        ///  rows of a matrix
-        template <>
-        struct size_by_dim_impl<1, matrix_tag>
-        {
-            /**
-             * \brief Compute the number of rows of the given matrix.
-             * \tparam ExprT A matrix expression type.
-             * \pre ExprT must be a model of MatrixExpression.
-             */
-            template <typename ExprT>
-            BOOST_UBLAS_INLINE
-            static typename ExprT::size_type apply(ExprT const& e)
-            {
-                return e.size1();
-            }
-        };
-
-
-        /// \brief Specialization of \c size_by_dim_impl for computing the number of
-        ///  columns of a matrix
-        template <>
-        struct size_by_dim_impl<2, matrix_tag>
-        {
-            /**
-             * \brief Compute the number of columns of the given matrix.
-             * \tparam ExprT A matrix expression type.
-             * \pre ExprT must be a model of MatrixExpression.
-             */
-            template <typename ExprT>
-            BOOST_UBLAS_INLINE
-            static typename ExprT::size_type apply(ExprT const& e)
-            {
-                return e.size2();
-            }
-        };
-
-
-        /**
-         * \brief Auxiliary class for computing the size of the given dimension for
-         *  a container of the given category and with the given orientation..
-         * \tparam Dim The dimension number (starting from 1).
-         * \tparam CategoryT The category type (e.g., vector_tag).
-         * \tparam OrientationT The orientation category type (e.g., row_major_tag).
-         */
-        template <typename TagT, typename CategoryT, typename OrientationT>
-        struct size_by_tag_impl;
-
-
-        /// \brief Specialization of \c size_by_tag_impl for computing the size of the
-        ///  major dimension of a row-major oriented matrix.
-        template <>
-        struct size_by_tag_impl<tag::major, matrix_tag, row_major_tag>
-        {
-            /**
-             * \brief Compute the number of rows of the given matrix.
-             * \tparam ExprT A matrix expression type.
-             * \pre ExprT must be a model of MatrixExpression.
-             */
-            template <typename ExprT>
-            BOOST_UBLAS_INLINE
-            static typename ExprT::size_type apply(ExprT const& e)
-            {
-                return e.size1();
-            }
-        };
-
-
-        /// \brief Specialization of \c size_by_tag_impl for computing the size of the
-        ///  minor dimension of a row-major oriented matrix.
-        template <>
-        struct size_by_tag_impl<tag::minor, matrix_tag, row_major_tag>
-        {
-            /**
-             * \brief Compute the number of columns of the given matrix.
-             * \tparam ExprT A matrix expression type.
-             * \pre ExprT must be a model of MatrixExpression.
-             */
-            template <typename ExprT>
-            BOOST_UBLAS_INLINE
-            static typename ExprT::size_type apply(ExprT const& e)
-            {
-                return e.size2();
-            }
-        };
-
-
-        /// \brief Specialization of \c size_by_tag_impl for computing the size of the
-        ///  leading dimension of a row-major oriented matrix.
-        template <>
-        struct size_by_tag_impl<tag::leading, matrix_tag, row_major_tag>
-        {
-            /**
-             * \brief Compute the number of columns of the given matrix.
-             * \tparam ExprT A matrix expression type.
-             * \pre ExprT must be a model of MatrixExpression.
-             */
-            template <typename ExprT>
-            BOOST_UBLAS_INLINE
-            static typename ExprT::size_type apply(ExprT const& e)
-            {
-                return e.size2();
-            }
-        };
-
-
-        /// \brief Specialization of \c size_by_tag_impl for computing the size of the
-        ///  major dimension of a column-major oriented matrix.
-        template <>
-        struct size_by_tag_impl<tag::major, matrix_tag, column_major_tag>
-        {
-            /**
-             * \brief Compute the number of columns of the given matrix.
-             * \tparam ExprT A matrix expression type.
-             * \pre ExprT must be a model of MatrixExpression.
-             */
-            template <typename ExprT>
-            BOOST_UBLAS_INLINE
-            static typename ExprT::size_type apply(ExprT const& e)
-            {
-                return e.size2();
-            }
-        };
-
-
-        /// \brief Specialization of \c size_by_tag_impl for computing the size of the
-        ///  minor dimension of a column-major oriented matrix.
-        template <>
-        struct size_by_tag_impl<tag::minor, matrix_tag, column_major_tag>
-        {
-            /**
-             * \brief Compute the number of rows of the given matrix.
-             * \tparam ExprT A matrix expression type.
-             * \pre ExprT must be a model of MatrixExpression.
-             */
-            template <typename ExprT>
-            BOOST_UBLAS_INLINE
-            static typename ExprT::size_type apply(ExprT const& e)
-            {
-                return e.size1();
-            }
-        };
-
-
-        /// \brief Specialization of \c size_by_tag_impl for computing the size of the
-        ///  leading dimension of a column-major oriented matrix.
-        template <>
-        struct size_by_tag_impl<tag::leading, matrix_tag, column_major_tag>
-        {
-            /**
-             * \brief Compute the number of rows of the given matrix.
-             * \tparam ExprT A matrix expression type.
-             * \pre ExprT must be a model of MatrixExpression.
-             */
-            template <typename ExprT>
-            BOOST_UBLAS_INLINE
-            static typename ExprT::size_type apply(ExprT const& e)
-            {
-                return e.size1();
-            }
-        };
 
-    } // Namespace detail
+/**
+ * \brief Specialization of \c size_by_tag_impl for computing the size of the
+ *  leading dimension of a row-major oriented matrix.
+ */
+template <>
+struct size_by_tag_impl<tag::leading, matrix_tag, row_major_tag>
+{
+    /**
+     * \brief Compute the number of columns of the given matrix.
+     * \tparam ExprT A matrix expression type.
+     * \pre ExprT must be a model of MatrixExpression.
+     */
+    template <typename ExprT>
+    BOOST_UBLAS_INLINE
+    static typename matrix_traits<ExprT>::size_type apply(matrix_expression<ExprT> const& me)
+    {
+        return me().size2();
+    }
+};
 
 
+/// \brief Specialization of \c size_by_tag_impl for computing the size of the
+///  major dimension of a column-major oriented matrix.
+template <>
+struct size_by_tag_impl<tag::major, matrix_tag, column_major_tag>
+{
     /**
-     * \brief Return the number of columns.
-     * \tparam MatrixExprT A type which models the matrix expression concept.
-     * \param m A matrix expression.
-     * \return The number of columns.
+     * \brief Compute the number of columns of the given matrix.
+     * \tparam ExprT A matrix expression type.
+     * \pre ExprT must be a model of MatrixExpression.
      */
-    template <typename VectorExprT>
+    template <typename ExprT>
     BOOST_UBLAS_INLINE
-    typename VectorExprT::size_type size(VectorExprT const& v)
+    static typename matrix_traits<ExprT>::size_type apply(matrix_expression<ExprT> const& me)
     {
-        return v.size();
+        return me().size2();
     }
+};
 
 
+/// \brief Specialization of \c size_by_tag_impl for computing the size of the
+///  minor dimension of a column-major oriented matrix.
+template <>
+struct size_by_tag_impl<tag::minor, matrix_tag, column_major_tag>
+{
     /**
-     * \brief Return the size of the given dimension for the given expression.
-     * \tparam Dim The dimension number (starting from 1).
-     * \tparam ExprT An expression type.
-     * \param e An expression.
-     * \return The number of columns.
-     * \return The size associated to the dimension \a Dim.
+     * \brief Compute the number of rows of the given matrix.
+     * \tparam ExprT A matrix expression type.
+     * \pre ExprT must be a model of MatrixExpression.
      */
-    template <std::size_t Dim, typename ExprT>
+    template <typename ExprT>
     BOOST_UBLAS_INLINE
-    typename ExprT::size_type size(ExprT const& e)
+    static typename matrix_traits<ExprT>::size_type apply(matrix_expression<ExprT> const& me)
     {
-        return detail::size_by_dim_impl<Dim, typename ExprT::type_category>::apply(e);
+        return me().size1();
     }
+};
 
 
+/// \brief Specialization of \c size_by_tag_impl for computing the size of the
+///  leading dimension of a column-major oriented matrix.
+template <>
+struct size_by_tag_impl<tag::leading, matrix_tag, column_major_tag>
+{
     /**
-     * \brief Return the size of the given dimension tag for the given expression.
-     * \tparam TagT The dimension tag type (e.g., tag::major).
-     * \tparam ExprT An expression type.
-     * \param e An expression.
-     * \return The size associated to the dimension tag \a TagT.
+     * \brief Compute the number of rows of the given matrix.
+     * \tparam ExprT A matrix expression type.
+     * \pre ExprT must be a model of MatrixExpression.
      */
-    template <typename TagT, typename ExprT>
+    template <typename ExprT>
     BOOST_UBLAS_INLINE
-    typename ExprT::size_type size(ExprT const& e)
+    static typename matrix_traits<ExprT>::size_type apply(matrix_expression<ExprT> const& me)
     {
-        return detail::size_by_tag_impl<TagT, typename ExprT::type_category, typename ExprT::orientation_category>::apply(e);
+        return me().size1();
     }
+};
+
+
+/// \brief Specialization of \c size_by_tag_impl for computing the size of the
+///  given dimension of a unknown oriented expression.
+template <typename TagT, typename CategoryT>
+struct size_by_tag_impl<TagT, CategoryT, unknown_orientation_tag>: size_by_tag_impl<TagT, CategoryT, row_major_tag>
+{
+    // Empty
+};
+
+}} // Namespace detail::<unnamed>
+
+
+/**
+ * \brief Return the number of columns.
+ * \tparam VectorExprT A type which models the vector expression concept.
+ * \param ve A vector expression.
+ * \return The length of the input vector expression.
+ */
+template <typename VectorExprT>
+BOOST_UBLAS_INLINE
+typename ::boost::lazy_enable_if_c<
+    detail::has_size_type<VectorExprT>::value,
+    detail::vector_size_type<VectorExprT>
+>::type size(vector_expression<VectorExprT> const& ve)
+{
+    return ve().size();
+}
+
+
+/**
+ * \brief Return the size of the given dimension for the given vector
+ *  expression.
+ * \tparam Dim The dimension number (starting from 1).
+ * \tparam VectorExprT A vector expression type.
+ * \param ve A vector expression.
+ * \return The length of the input vector expression.
+ */
+template <std::size_t Dim, typename VectorExprT>
+BOOST_UBLAS_INLINE
+typename vector_traits<VectorExprT>::size_type size(vector_expression<VectorExprT> const& ve)
+{
+    return detail::size_by_dim_impl<Dim, vector_tag>::template apply(ve);
+}
+
+
+/**
+ * \brief Return the size of the given dimension for the given matrix
+ *  expression.
+ * \tparam Dim The dimension number (starting from 1).
+ * \tparam MatrixExprT A matrix expression type.
+ * \param e A matrix expression.
+ * \return The size of the input matrix expression associated to the dimension
+ *  \a Dim.
+ */
+template <std::size_t Dim, typename MatrixExprT>
+BOOST_UBLAS_INLINE
+typename matrix_traits<MatrixExprT>::size_type size(matrix_expression<MatrixExprT> const& me)
+{
+    return detail::size_by_dim_impl<Dim, matrix_tag>::template apply(me);
+}
+
+
+/**
+ * \brief Return the size of the given dimension tag for the given matrix
+ *  expression.
+ * \tparam TagT The dimension tag type (e.g., tag::major).
+ * \tparam MatrixExprT A matrix expression type.
+ * \param e A matrix expression.
+ * \return The size of the input matrix expression associated to the dimension
+ *  tag \a TagT.
+ */
+template <typename TagT, typename MatrixExprT>
+BOOST_UBLAS_INLINE
+typename ::boost::lazy_enable_if_c<
+    detail::has_size_type<MatrixExprT>::value,
+    detail::matrix_size_type<MatrixExprT>
+>::type size(matrix_expression<MatrixExprT> const& me)
+{
+    return detail::size_by_tag_impl<TagT, matrix_tag, typename matrix_traits<MatrixExprT>::orientation_category>::template apply(me);
+}
 
 }}} // Namespace boost::numeric::ublas