/**
 * -*- c++ -*-
 *
 * \file begin.hpp
 *
 * \brief The \c begin operation.
 *
 * Copyright (c) 2009, Marco Guazzone
 *
 * Distributed under the Boost Software License, Version 1.0. (See
 * accompanying file LICENSE_1_0.txt or copy at
 * http://www.boost.org/LICENSE_1_0.txt)
 *
 * \author Marco Guazzone, marco.guazzone@gmail.com
 */

#ifndef BOOST_NUMERIC_UBLAS_OPERATION_BEGIN_HPP
#define BOOST_NUMERIC_UBLAS_OPERATION_BEGIN_HPP


#include <boost/numeric/ublas/expression_types.hpp>
#include <boost/numeric/ublas/fwd.hpp>
#include <boost/numeric/ublas/traits/const_iterator_type.hpp>
#include <boost/numeric/ublas/traits/iterator_type.hpp>


namespace boost { namespace numeric { namespace ublas {

    namespace detail {

        /**
         * \brief Auxiliary class for implementing the \c begin operation.
         * \tparam CategoryT The expression category type (e.g., vector_tag).
         * \tparam TagT The dimension type tag (e.g., tag::major).
         * \tparam OrientationT The orientation category type (e.g., row_major_tag).
         */
        template <typename CategoryT, typename TagT=void, typename OrientationT=void>
        struct begin_impl;


        /// \brief Specialization of \c begin_impl for iterating vector expressions.
        template <>
        struct begin_impl<vector_tag,void,void>
        {
            /**
             * \brief Return an iterator to the first element of the given vector
             *  expression.
             * \tparam ExprT A model of VectorExpression type.
             * \param e A vector expression.
             * \return An iterator over the given vector expression.
             */
            template <typename ExprT>
            static typename ExprT::iterator apply(ExprT& e)
            {
                return e.begin();
            }


            /**
             * \brief Return a const iterator to the first element of the given vector
             *  expression.
             * \tparam ExprT A model of VectorExpression type.
             * \param e A vector expression.
             * \return A const iterator to the first element of the given vector
             *  expression.
             */
            template <typename ExprT>
            static typename ExprT::const_iterator apply(ExprT const& e)
            {
                return e.begin();
            }
        };


        /// \brief Specialization of \c begin_impl for iterating matrix expressions with
        ///  a row-major orientation over the major dimension.
        template <>
        struct begin_impl<matrix_tag,tag::major,row_major_tag>
        {
            /**
             * \brief Return an iterator to the first element of the given row-major
             *  matrix expression over the major dimension.
             * \tparam ExprT A model of MatrixExpression type.
             * \param e A matrix expression.
             * \return An iterator over the major dimension of the given matrix
             *  expression.
             */
            template <typename ExprT>
            static typename ExprT::iterator1 apply(ExprT& e)
            {
                return e.begin1();
            }


            /**
             * \brief Return a const iterator to the first element of the given
             *  row-major matrix expression over the major dimension.
             * \tparam ExprT A model of MatrixExpression type.
             * \param e A matrix expression.
             * \return A const iterator over the major dimension of the given matrix
             *  expression.
             */
            template <typename ExprT>
            static typename ExprT::const_iterator1 apply(ExprT const& e)
            {
                return e.begin1();
            }
        };


        /// \brief Specialization of \c begin_impl for iterating matrix expressions with
        ///  a column-major orientation over the major dimension.
        template <>
        struct begin_impl<matrix_tag,tag::major,column_major_tag>
        {
            /**
             * \brief Return an iterator to the first element of the given column-major
             *  matrix expression over the major dimension.
             * \tparam ExprT A model of MatrixExpression type.
             * \param e A matrix expression.
             * \return An iterator over the major dimension of the given matrix
             *  expression.
             */
            template <typename ExprT>
            static typename ExprT::iterator2 apply(ExprT& e)
            {
                return e.begin2();
            }


            /**
             * \brief Return a const iterator to the first element of the given
             *  column-major matrix expression over the major dimension.
             * \tparam ExprT A model of MatrixExpression type.
             * \param e A matrix expression.
             * \return A const iterator over the major dimension of the given matrix
             *  expression.
             */
            template <typename ExprT>
            static typename ExprT::const_iterator2 apply(ExprT const& e)
            {
                return e.begin2();
            }
        };


        /// \brief Specialization of \c begin_impl for iterating matrix expressions with
        ///  a row-major orientation over the minor dimension.
        template <>
        struct begin_impl<matrix_tag,tag::minor,row_major_tag>
        {
            /**
             * \brief Return an iterator to the first element of the given row-major
             *  matrix expression over the minor dimension.
             * \tparam ExprT A model of MatrixExpression type.
             * \param e A matrix expression.
             * \return An iterator over the minor dimension of the given matrix
             *  expression.
             */
            template <typename ExprT>
            static typename ExprT::iterator2 apply(ExprT& e)
            {
                return e.begin2();
            }


            /**
             * \brief Return a const iterator to the first element of the given
             *  row-major matrix expression over the minor dimension.
             * \tparam ExprT A model of MatrixExpression type.
             * \param e A matrix expression.
             * \return A const iterator over the minor dimension of the given matrix
             *  expression.
             */
            template <typename ExprT>
            static typename ExprT::const_iterator2 apply(ExprT const& e)
            {
                return e.begin2();
            }
        };


        /// \brief Specialization of \c begin_impl for iterating matrix expressions with
        ///  a column-major orientation over the minor dimension.
        template <>
        struct begin_impl<matrix_tag,tag::minor,column_major_tag>
        {
            /**
             * \brief Return an iterator to the first element of the given column-major
             *  matrix expression over the minor dimension.
             * \tparam ExprT A model of MatrixExpression type.
             * \param e A matrix expression.
             * \return An iterator over the minor dimension of the given matrix
             *  expression.
             */
            template <typename ExprT>
            static typename ExprT::iterator1 apply(ExprT& e)
            {
                return e.begin1();
            }


            /**
             * \brief Return a const iterator to the first element of the given
             *  column-major matrix expression over the minor dimension.
             * \tparam ExprT A model of MatrixExpression type.
             * \param e A matrix expression.
             * \return A const iterator over the minor dimension of the given matrix
             *  expression.
             */
            template <typename ExprT>
            static typename ExprT::const_iterator1 apply(ExprT const& e)
            {
                return e.begin1();
            }
        };

    } // Namespace detail


    /**
     * \brief An iterator to the first element of the given vector expression.
     * \tparam ExprT A model of VectorExpression type.
     * \param e A vector expression.
     * \return An iterator to the first element of the given vector expression.
     */
    template <typename ExprT>
    BOOST_UBLAS_INLINE
    typename ExprT::iterator begin(vector_expression<ExprT>& e)
    {
        return detail::begin_impl<typename ExprT::type_category>::apply(e());
    }


    /**
     * \brief A const iterator to the first element of the given vector expression.
     * \tparam ExprT A model of VectorExpression type.
     * \param e A vector expression.
     * \return A const iterator to the first element of the given vector expression.
     */
    template <typename ExprT>
    BOOST_UBLAS_INLINE
    typename ExprT::const_iterator begin(vector_expression<ExprT> const& e)
    {
        return detail::begin_impl<typename ExprT::type_category>::apply(e());
    }


    /**
     * \brief An iterator to the first element of the given matrix expression
     *  according to its orientation.
     * \tparam DimTagT A dimension tag type (e.g., tag::major).
     * \tparam ExprT A model of MatrixExpression type.
     * \param e A matrix expression.
     * \return An iterator to the first element of the given matrix expression
     *  according to its orientation.
     */
    template <typename TagT, typename ExprT>
    BOOST_UBLAS_INLINE
    typename iterator_type<ExprT,TagT>::type begin(matrix_expression<ExprT>& e)
    {
        return detail::begin_impl<typename ExprT::type_category, TagT, typename ExprT::orientation_category>::apply(e());
    }


    /**
     * \brief A const iterator to the first element of the given matrix expression
     *  according to its orientation.
     * \tparam TagT A dimension tag type (e.g., tag::major).
     * \tparam ExprT A model of MatrixExpression type.
     * \param e A matrix expression.
     * \return A const iterator to the first element of the given matrix expression
     *  according to its orientation.
     */
    template <typename TagT, typename ExprT>
    BOOST_UBLAS_INLINE
    typename const_iterator_type<ExprT,TagT>::type begin(matrix_expression<ExprT> const& e)
    {
        return detail::begin_impl<typename ExprT::type_category, TagT, typename ExprT::orientation_category>::apply(e());
    }


    /**
     * \brief An iterator to the first element over the dual dimension of the given
     *  iterator.
     * \tparam IteratorT A model of Iterator type.
     * \param it An iterator.
     * \return An iterator to the first element over the dual dimension of the given
     *  iterator.
     */
    template <typename IteratorT>
    BOOST_UBLAS_INLINE
    typename IteratorT::dual_iterator_type begin(IteratorT& it)
    {
        return it.begin();
    }


    /**
     * \brief A const iterator to the first element over the dual dimension of the
     *  given iterator.
     * \tparam IteratorT A model of Iterator type.
     * \param it An iterator.
     * \return A const iterator to the first element over the dual dimension of the
     *  given iterator.
     */
    template <typename IteratorT>
    BOOST_UBLAS_INLINE
    typename IteratorT::dual_iterator_type begin(IteratorT const& it)
    {
        return it.begin();
    }

}}} // Namespace boost::numeric::ublas


#endif // BOOST_NUMERIC_UBLAS_OPERATION_BEGIN_HPP