    // Copyright (C) 2006  Davis E. King (davis@dlib.net)
    // License: Boost Software License   See LICENSE.txt for the full license.
    #ifndef DLIB_MATRIx_SUBEXP_
    #define DLIB_MATRIx_SUBEXP_

    #include "matrix_subexp_abstract.h"
    #include "matrix_op.h"
    #include "matrix.h"
    #include "../geometry/rectangle.h"
    #include "matrix_expressions.h"
    #include "matrix_mat.h"

    namespace dlib
    {

    // ----------------------------------------------------------------------------------------
    // ----------------------------------------------------------------------------------------
    // ----------------------------------------------------------------------------------------

        template <long start, long inc, long end>
        const matrix_range_static_exp<start,inc,end> range (
        )
        {
            COMPILE_TIME_ASSERT(inc > 0);
            return matrix_range_static_exp<start,inc,end>();
        }

        template <long start, long end>
        const matrix_range_static_exp<start,1,end> range (
        )
        {
            return matrix_range_static_exp<start,1,end>();
        }

        inline const matrix_range_exp<long> range (
            long start,
            long end
        )
        {
            return matrix_range_exp<long>(start,end);
        }

        inline const matrix_range_exp<long> range (
            long start,
            long inc,
            long end
        )
        {
            DLIB_ASSERT(inc > 0,
                "\tconst matrix_exp range(start, inc, end)"
                << "\n\tInvalid inputs to this function"
                << "\n\tstart: " << start
                << "\n\tinc:   " << inc
                << "\n\tend:   " << end
                );

            return matrix_range_exp<long>(start,inc,end);
        }

    // ----------------------------------------------------------------------------------------

        template <typename M>
        struct op_subm
        {
            op_subm (
                const M& m_x,
                const long& r_x,
                const long& c_x,
                const long& nr_x,
                const long& nc_x
            ) : m(m_x), r_(r_x), c_(c_x), nr_(nr_x), nc_(nc_x) { }

            const M& m;
            const long r_;
            const long c_;
            const long nr_;
            const long nc_;

            const static long cost = M::cost+1;
            typedef typename M::type type;
            typedef typename M::const_ret_type const_ret_type;
            typedef typename M::mem_manager_type mem_manager_type;
            typedef typename M::layout_type layout_type;
            const static long NR = 0;
            const static long NC = 0;

            const_ret_type apply ( long r, long c) const { return m(r+r_,c+c_); }

            long nr () const { return nr_; }
            long nc () const { return nc_; }

            template <typename U> bool aliases               ( const matrix_exp<U>& item) const { return m.aliases(item); }
            template <typename U> bool destructively_aliases ( const matrix_exp<U>& item) const { return m.aliases(item); }
        };

        template <
            typename EXP
            >
        const matrix_op<op_subm<EXP> > subm (
            const matrix_exp<EXP>& m,
            long r,
            long c,
            long nr,
            long nc
        )
        {
            DLIB_ASSERT(r >= 0 && c >= 0 && nr >= 0 && nc >= 0 && r+nr <= m.nr() && c+nc <= m.nc(),
                "\tconst matrix_exp subm(const matrix_exp& m, r, c, nr, nc)"
                << "\n\tYou have specified invalid sub matrix dimensions"
                << "\n\tm.nr(): " << m.nr()
                << "\n\tm.nc(): " << m.nc()
                << "\n\tr:      " << r
                << "\n\tc:      " << c
                << "\n\tnr:     " << nr
                << "\n\tnc:     " << nc
                );

            typedef op_subm<EXP> op;
            return matrix_op<op>(op(m.ref(),r,c,nr,nc));
        }

    // ----------------------------------------------------------------------------------------

        template <
            typename EXP
            >
        const matrix_op<op_subm<EXP> > subm_clipped (
            const matrix_exp<EXP>& m,
            long r,
            long c,
            long nr,
            long nc
        )
        {
            rectangle box(c,r,c+nc-1,r+nr-1);
            box = box.intersect(get_rect(m));
            typedef op_subm<EXP> op;
            return matrix_op<op>(op(m.ref(),box.top(),box.left(),box.height(),box.width()));
        }

    // ----------------------------------------------------------------------------------------

        template <
            typename EXP
            >
        const matrix_op<op_subm<EXP> > subm (
            const matrix_exp<EXP>& m,
            const rectangle& rect
        )
        {
            DLIB_ASSERT(get_rect(m).contains(rect) == true,
                "\tconst matrix_exp subm(const matrix_exp& m, const rectangle& rect)"
                << "\n\tYou have specified invalid sub matrix dimensions"
                << "\n\tm.nr(): " << m.nr()
                << "\n\tm.nc(): " << m.nc()
                << "\n\trect.left():   " << rect.left()
                << "\n\trect.top():    " << rect.top()
                << "\n\trect.right():  " << rect.right()
                << "\n\trect.bottom(): " << rect.bottom()
                );

            typedef op_subm<EXP> op;
            return matrix_op<op>(op(m.ref(),rect.top(),rect.left(),rect.height(),rect.width()));
        }

    // ----------------------------------------------------------------------------------------

        template <
            typename EXP
            >
        const matrix_op<op_subm<EXP> > subm_clipped (
            const matrix_exp<EXP>& m,
            rectangle rect
        )
        {
            rect = rect.intersect(get_rect(m));

            typedef op_subm<EXP> op;
            return matrix_op<op>(op(m.ref(),rect.top(),rect.left(),rect.height(),rect.width()));
        }

    // ----------------------------------------------------------------------------------------

        template <typename M1, typename M2, typename M3>
        struct op_subm_range
        {
            op_subm_range( const M1& m1_, const M2& rows_, const M3& cols_) :
                m1(m1_), rows(rows_), cols(cols_) {}
            const M1& m1;
            const M2& rows;
            const M3& cols;

            const static long cost = M1::cost+M2::cost+M3::cost;
            typedef typename M1::type type;
            typedef typename M1::const_ret_type const_ret_type;
            typedef typename M1::mem_manager_type mem_manager_type;
            typedef typename M1::layout_type layout_type;
            const static long NR = M2::NC*M2::NR;
            const static long NC = M3::NC*M3::NR;

            const_ret_type apply ( long r, long c) const { return m1(rows(r),cols(c)); }

            long nr () const { return rows.size(); }
            long nc () const { return cols.size(); }

            template <typename U> bool aliases               ( const matrix_exp<U>& item) const
            { return m1.aliases(item) || rows.aliases(item) || cols.aliases(item); }
            template <typename U> bool destructively_aliases ( const matrix_exp<U>& item) const
            { return m1.aliases(item) || rows.aliases(item) || cols.aliases(item); }
        };

        template <
            typename EXP,
            typename EXPr,
            typename EXPc
            >
        const matrix_op<op_subm_range<EXP,EXPr,EXPc> > subm (
            const matrix_exp<EXP>& m,
            const matrix_exp<EXPr>& rows,
            const matrix_exp<EXPc>& cols
        )
        {
            // the rows and cols matrices must contain integer elements
            COMPILE_TIME_ASSERT(std::numeric_limits<typename EXPr::type>::is_integer);
            COMPILE_TIME_ASSERT(std::numeric_limits<typename EXPc::type>::is_integer);

            DLIB_ASSERT(0 <= min(rows) && max(rows) < m.nr() && 0 <= min(cols) && max(cols) < m.nc() &&
                        (rows.nr() == 1 || rows.nc() == 1) && (cols.nr() == 1 || cols.nc() == 1),
                "\tconst matrix_exp subm(const matrix_exp& m, const matrix_exp& rows, const matrix_exp& cols)"
                << "\n\tYou have given invalid arguments to this function"
                << "\n\tm.nr():     " << m.nr()
                << "\n\tm.nc():     " << m.nc()
                << "\n\tmin(rows):  " << min(rows)
                << "\n\tmax(rows):  " << max(rows)
                << "\n\tmin(cols):  " << min(cols)
                << "\n\tmax(cols):  " << max(cols)
                << "\n\trows.nr():  " << rows.nr()
                << "\n\trows.nc():  " << rows.nc()
                << "\n\tcols.nr():  " << cols.nr()
                << "\n\tcols.nc():  " << cols.nc()
                );

            typedef op_subm_range<EXP,EXPr,EXPc> op;
            return matrix_op<op>(op(m.ref(),rows.ref(),cols.ref()));
        }

    // ----------------------------------------------------------------------------------------

        template <typename M>
        struct op_rowm
        {
            op_rowm(const M& m_, const long& row_) : m(m_), row(row_) {}
            const M& m;
            const long row;

            const static long cost = M::cost;
            const static long NR = 1;
            const static long NC = M::NC;
            typedef typename M::type type;
            typedef typename M::const_ret_type const_ret_type;
            typedef typename M::mem_manager_type mem_manager_type;
            typedef typename M::layout_type layout_type;
            const_ret_type apply ( long, long c) const { return m(row,c); }

            long nr () const { return 1; }
            long nc () const { return m.nc(); }

            template <typename U> bool aliases               ( const matrix_exp<U>& item) const { return m.aliases(item); }
            template <typename U> bool destructively_aliases ( const matrix_exp<U>& item) const { return m.aliases(item); }
        };

        template <
            typename EXP
            >
        const matrix_op<op_rowm<EXP> > rowm (
            const matrix_exp<EXP>& m,
            long row
        )
        {
            DLIB_ASSERT(row >= 0 && row < m.nr(),
                "\tconst matrix_exp rowm(const matrix_exp& m, row)"
                << "\n\tYou have specified invalid sub matrix dimensions"
                << "\n\tm.nr(): " << m.nr()
                << "\n\tm.nc(): " << m.nc()
                << "\n\trow:    " << row
                );

            typedef op_rowm<EXP> op;
            return matrix_op<op>(op(m.ref(),row));
        }

        template <typename EXP>
        struct rowm_exp
        {
            typedef matrix_op<op_rowm<EXP> > type;
        };

    // ----------------------------------------------------------------------------------------

        template <typename M>
        struct op_rowm2
        {
            op_rowm2(const M& m_, const long& row_, const long& len) : m(m_), row(row_), length(len) {}
            const M& m;
            const long row;
            const long length;

            const static long cost = M::cost;
            const static long NR = 1;
            const static long NC = 0;
            typedef typename M::type type;
            typedef typename M::const_ret_type const_ret_type;
            typedef typename M::mem_manager_type mem_manager_type;
            typedef typename M::layout_type layout_type;
            const_ret_type apply ( long , long c) const { return m(row,c); }

            long nr () const { return 1; }
            long nc () const { return length; }

            template <typename U> bool aliases               ( const matrix_exp<U>& item) const { return m.aliases(item); }
            template <typename U> bool destructively_aliases ( const matrix_exp<U>& item) const { return m.aliases(item); }
        };

        template <
            typename EXP
            >
        const matrix_op<op_rowm2<EXP> > rowm (
            const matrix_exp<EXP>& m,
            long row,
            long length
        )
        {
            DLIB_ASSERT(row >= 0 && row < m.nr() &&
                        length >= 0 && length <= m.nc(),
                "\tconst matrix_exp rowm(const matrix_exp& m, row, length)"
                << "\n\tYou have specified invalid sub matrix dimensions"
                << "\n\tm.nr(): " << m.nr()
                << "\n\tm.nc(): " << m.nc()
                << "\n\trow:    " << row
                << "\n\tlength: " << length
                );

            typedef op_rowm2<EXP> op;
            return matrix_op<op>(op(m.ref(), row, length));
        }

    // ----------------------------------------------------------------------------------------

        template <typename M1, typename M2>
        struct op_rowm_range
        {
            op_rowm_range( const M1& m1_, const M2& rows_) : m1(m1_), rows(rows_) {}
            const M1& m1;
            const M2& rows;

            const static long cost = M1::cost+M2::cost;
            typedef typename M1::type type;
            typedef typename M1::const_ret_type const_ret_type;
            typedef typename M1::mem_manager_type mem_manager_type;
            typedef typename M1::layout_type layout_type;
            const static long NR = M2::NC*M2::NR;
            const static long NC = M1::NC;

            const_ret_type apply ( long r, long c) const { return m1(rows(r),c); }

            long nr () const { return rows.size(); }
            long nc () const { return m1.nc(); }

            template <typename U> bool aliases               ( const matrix_exp<U>& item) const
            { return m1.aliases(item) || rows.aliases(item); }
            template <typename U> bool destructively_aliases ( const matrix_exp<U>& item) const
            { return m1.aliases(item) || rows.aliases(item); }
        };

        template <
            typename EXP1,
            typename EXP2
            >
        const matrix_op<op_rowm_range<EXP1,EXP2> > rowm (
            const matrix_exp<EXP1>& m,
            const matrix_exp<EXP2>& rows
        )
        {
            // the rows matrix must contain integer elements
            COMPILE_TIME_ASSERT(std::numeric_limits<typename EXP2::type>::is_integer);

            DLIB_ASSERT(0 <= min(rows) && max(rows) < m.nr() && (rows.nr() == 1 || rows.nc() == 1),
                "\tconst matrix_exp rowm(const matrix_exp& m, const matrix_exp& rows)"
                << "\n\tYou have given invalid arguments to this function"
                << "\n\tm.nr():     " << m.nr()
                << "\n\tm.nc():     " << m.nc()
                << "\n\tmin(rows):  " << min(rows)
                << "\n\tmax(rows):  " << max(rows)
                << "\n\trows.nr():  " << rows.nr()
                << "\n\trows.nc():  " << rows.nc()
                );

            typedef op_rowm_range<EXP1,EXP2> op;
            return matrix_op<op>(op(m.ref(),rows.ref()));
        }

    // ----------------------------------------------------------------------------------------

        template <typename M>
        struct op_colm
        {
            op_colm(const M& m_, const long& col_) : m(m_), col(col_) {}
            const M& m;
            const long col;

            const static long cost = M::cost;
            const static long NR = M::NR;
            const static long NC = 1;
            typedef typename M::type type;
            typedef typename M::const_ret_type const_ret_type;
            typedef typename M::mem_manager_type mem_manager_type;
            typedef typename M::layout_type layout_type;
            const_ret_type apply ( long r, long) const { return m(r,col); }

            long nr () const { return m.nr(); }
            long nc () const { return 1; }

            template <typename U> bool aliases               ( const matrix_exp<U>& item) const { return m.aliases(item); }
            template <typename U> bool destructively_aliases ( const matrix_exp<U>& item) const { return m.aliases(item); }
        };

        template <
            typename EXP
            >
        const matrix_op<op_colm<EXP> > colm (
            const matrix_exp<EXP>& m,
            long col
        )
        {
            DLIB_ASSERT(col >= 0 && col < m.nc(),
                "\tconst matrix_exp colm(const matrix_exp& m, row)"
                << "\n\tYou have specified invalid sub matrix dimensions"
                << "\n\tm.nr(): " << m.nr()
                << "\n\tm.nc(): " << m.nc()
                << "\n\tcol:    " << col
                );

            typedef op_colm<EXP> op;
            return matrix_op<op>(op(m.ref(),col));
        }

        template <typename EXP>
        struct colm_exp
        {
            typedef matrix_op<op_colm<EXP> > type;
        };

    // ----------------------------------------------------------------------------------------

        template <typename M>
        struct op_colm2
        {
            op_colm2(const M& m_, const long& col_, const long& len) : m(m_), col(col_), length(len) {}
            const M& m;
            const long col;
            const long length;

            const static long cost = M::cost;
            const static long NR = 0;
            const static long NC = 1;
            typedef typename M::type type;
            typedef typename M::const_ret_type const_ret_type;
            typedef typename M::mem_manager_type mem_manager_type;
            typedef typename M::layout_type layout_type;
            const_ret_type apply ( long r, long ) const { return m(r,col); }

            long nr () const { return length; }
            long nc () const { return 1; }

            template <typename U> bool aliases               ( const matrix_exp<U>& item) const { return m.aliases(item); }
            template <typename U> bool destructively_aliases ( const matrix_exp<U>& item) const { return m.aliases(item); }
        };

        template <
            typename EXP
            >
        const matrix_op<op_colm2<EXP> > colm (
            const matrix_exp<EXP>& m,
            long col,
            long length
        )
        {
            DLIB_ASSERT(col >= 0 && col < m.nc() &&
                        length >= 0 && length <= m.nr(),
                "\tconst matrix_exp colm(const matrix_exp& m, col, length)"
                << "\n\tYou have specified invalid sub matrix dimensions"
                << "\n\tm.nr(): " << m.nr()
                << "\n\tm.nc(): " << m.nc()
                << "\n\tcol:    " << col
                << "\n\tlength: " << length
                );

            typedef op_colm2<EXP> op;
            return matrix_op<op>(op(m.ref(),col, length));
        }

    // ----------------------------------------------------------------------------------------

        template <typename M1, typename M2>
        struct op_colm_range
        {
            op_colm_range( const M1& m1_, const M2& cols_) : m1(m1_), cols(cols_) {}
            const M1& m1;
            const M2& cols;

            typedef typename M1::type type;
            typedef typename M1::const_ret_type const_ret_type;
            typedef typename M1::mem_manager_type mem_manager_type;
            typedef typename M1::layout_type layout_type;
            const static long NR = M1::NR;
            const static long NC = M2::NC*M2::NR;
            const static long cost = M1::cost+M2::cost;

            const_ret_type apply (long r, long c) const { return m1(r,cols(c)); }

            long nr () const { return m1.nr(); }
            long nc () const { return cols.size(); }

            template <typename U> bool aliases               ( const matrix_exp<U>& item) const
            { return m1.aliases(item) || cols.aliases(item); }
            template <typename U> bool destructively_aliases ( const matrix_exp<U>& item) const
            { return m1.aliases(item) || cols.aliases(item); }
        };

        template <
            typename EXP1,
            typename EXP2
            >
        const matrix_op<op_colm_range<EXP1,EXP2> > colm (
            const matrix_exp<EXP1>& m,
            const matrix_exp<EXP2>& cols
        )
        {
            // the rows matrix must contain integer elements
            COMPILE_TIME_ASSERT(std::numeric_limits<typename EXP2::type>::is_integer);

            DLIB_ASSERT(0 <= min(cols) && max(cols) < m.nc() && (cols.nr() == 1 || cols.nc() == 1),
                "\tconst matrix_exp colm(const matrix_exp& m, const matrix_exp& cols)"
                << "\n\tYou have given invalid arguments to this function"
                << "\n\tm.nr():     " << m.nr()
                << "\n\tm.nc():     " << m.nc()
                << "\n\tmin(cols):  " << min(cols)
                << "\n\tmax(cols):  " << max(cols)
                << "\n\tcols.nr():  " << cols.nr()
                << "\n\tcols.nc():  " << cols.nc()
                );

            typedef op_colm_range<EXP1,EXP2> op;
            return matrix_op<op>(op(m.ref(),cols.ref()));
        }

    // ----------------------------------------------------------------------------------------

        template <typename T>
        class assignable_ptr_matrix
        {
        public:
            typedef T type;
            typedef row_major_layout layout_type;
            typedef matrix<T,0,0,default_memory_manager,layout_type> matrix_type;

            assignable_ptr_matrix(
                T* ptr_,
                long nr_,
                long nc_
            ) : ptr(ptr_), height(nr_), width(nc_){}

            T& operator() (
                long r,
                long c
            )
            {
                return ptr[r*width + c];
            }

            const T& operator() (
                long r,
                long c
            ) const
            {
                return ptr[r*width + c];
            }

            long nr() const { return height; }
            long nc() const { return width; }

            template <typename EXP>
            assignable_ptr_matrix& operator= (
                const matrix_exp<EXP>& exp
            )
            {
                // You can only assign to a set_ptrm() expression with a source matrix that
                // contains the same type of elements as the target (i.e. you can't mix double
                // and float types).
                COMPILE_TIME_ASSERT((is_same_type<T, typename EXP::type>::value == true));

                DLIB_ASSERT( exp.nr() == height && exp.nc() == width,
                    "\tassignable_matrix_expression set_ptrm()"
                    << "\n\tYou have tried to assign to this object using a matrix that isn't the right size"
                    << "\n\texp.nr() (source matrix): " << exp.nr()
                    << "\n\texp.nc() (source matrix): " << exp.nc()
                    << "\n\twidth (target matrix):    " << width
                    << "\n\theight (target matrix):   " << height
                    );

                if (exp.destructively_aliases(mat(ptr,height,width)) == false)
                {
                    matrix_assign(*this, exp);
                }
                else
                {
                    // make a temporary copy of the matrix we are going to assign to ptr to
                    // avoid aliasing issues during the copy
                    this->operator=(tmp(exp));
                }

                return *this;
            }

            template <typename EXP>
            assignable_ptr_matrix& operator+= (
                const matrix_exp<EXP>& exp
            )
            {
                // You can only assign to a set_ptrm() expression with a source matrix that
                // contains the same type of elements as the target (i.e. you can't mix double
                // and float types).
                COMPILE_TIME_ASSERT((is_same_type<T, typename EXP::type>::value == true));

                DLIB_ASSERT( exp.nr() == height && exp.nc() == width,
                    "\tassignable_matrix_expression set_ptrm()"
                    << "\n\tYou have tried to assign to this object using a matrix that isn't the right size"
                    << "\n\texp.nr() (source matrix): " << exp.nr()
                    << "\n\texp.nc() (source matrix): " << exp.nc()
                    << "\n\twidth (target matrix):    " << width
                    << "\n\theight (target matrix):   " << height
                    );

                if (exp.destructively_aliases(mat(ptr,height,width)) == false)
                {
                    matrix_assign(*this, mat(ptr,height,width)+exp);
                }
                else
                {
                    // make a temporary copy of the matrix we are going to assign to ptr to
                    // avoid aliasing issues during the copy
                    this->operator+=(tmp(exp));
                }

                return *this;
            }

            template <typename EXP>
            assignable_ptr_matrix& operator-= (
                const matrix_exp<EXP>& exp
            )
            {
                // You can only assign to a set_ptrm() expression with a source matrix that
                // contains the same type of elements as the target (i.e. you can't mix double
                // and float types).
                COMPILE_TIME_ASSERT((is_same_type<T, typename EXP::type>::value == true));

                DLIB_ASSERT( exp.nr() == height && exp.nc() == width,
                    "\tassignable_matrix_expression set_ptrm()"
                    << "\n\tYou have tried to assign to this object using a matrix that isn't the right size"
                    << "\n\texp.nr() (source matrix): " << exp.nr()
                    << "\n\texp.nc() (source matrix): " << exp.nc()
                    << "\n\twidth (target matrix):    " << width
                    << "\n\theight (target matrix):   " << height
                    );

                if (exp.destructively_aliases(mat(ptr,height,width)) == false)
                {
                    matrix_assign(*this, mat(ptr,height,width)-exp);
                }
                else
                {
                    // make a temporary copy of the matrix we are going to assign to ptr to
                    // avoid aliasing issues during the copy
                    this->operator-=(tmp(exp));
                }

                return *this;
            }

            assignable_ptr_matrix& operator= (
                const T& value
            )
            {
                const long size = width*height;
                for (long i = 0; i < size; ++i)
                    ptr[i] = value;

                return *this;
            }

            assignable_ptr_matrix& operator+= (
                const T& value
            )
            {
                const long size = width*height;
                for (long i = 0; i < size; ++i)
                    ptr[i] += value;

                return *this;
            }

            assignable_ptr_matrix& operator-= (
                const T& value
            )
            {
                const long size = width*height;
                for (long i = 0; i < size; ++i)
                    ptr[i] -= value;

                return *this;
            }

            T* ptr;
            const long height;
            const long width;
        };

        template <typename T>
        assignable_ptr_matrix<T> set_ptrm (
            T* ptr,
            long nr,
            long nc = 1
        )
        {
            DLIB_ASSERT(nr >= 0 && nc >= 0,
                "\t assignable_matrix_expression set_ptrm(T* ptr, long nr, long nc)"
                << "\n\t The dimensions can't be negative."
                << "\n\t nr: " << nr
                << "\n\t nc: " << nc
                );

            return assignable_ptr_matrix<T>(ptr,nr,nc);
        }

    // ----------------------------------------------------------------------------------------

        template <typename T, long NR, long NC, typename mm, typename l>
        class assignable_sub_matrix
        {
        public:
            typedef T type;
            typedef l layout_type;
            typedef matrix<T,NR,NC,mm,l> matrix_type;

            assignable_sub_matrix(
                matrix<T,NR,NC,mm,l>& m_,
                long top_,
                long left_,
                long height_,
                long width_
            ) : m(m_), left(left_), top(top_), width(width_), height(height_) {}

            T& operator() (
                long r,
                long c
            )
            {
                return m(r+top,c+left);
            }

            const T& operator() (
                long r,
                long c
            ) const
            {
                return m(r+top,c+left);
            }

            long nr() const { return height; }
            long nc() const { return width; }

            template <typename EXP>
            assignable_sub_matrix& operator= (
                const matrix_exp<EXP>& exp
            )
            {
                DLIB_ASSERT( exp.nr() == height && exp.nc() == width,
                    "\tassignable_matrix_expression set_subm()"
                    << "\n\tYou have tried to assign to this object using a matrix that isn't the right size"
                    << "\n\texp.nr() (source matrix): " << exp.nr()
                    << "\n\texp.nc() (source matrix): " << exp.nc()
                    << "\n\twidth (target matrix):    " << width
                    << "\n\theight (target matrix):   " << height
                    );

                if (exp.destructively_aliases(m) == false)
                {
                    matrix_assign(*this, exp);
                }
                else
                {
                    // make a temporary copy of the matrix we are going to assign to m to
                    // avoid aliasing issues during the copy
                    this->operator=(tmp(exp));
                }

                return *this;
            }

            template <typename EXP>
            assignable_sub_matrix& operator+= (
                const matrix_exp<EXP>& exp
            )
            {
                DLIB_ASSERT( exp.nr() == height && exp.nc() == width,
                    "\tassignable_matrix_expression set_subm()"
                    << "\n\tYou have tried to assign to this object using a matrix that isn't the right size"
                    << "\n\texp.nr() (source matrix): " << exp.nr()
                    << "\n\texp.nc() (source matrix): " << exp.nc()
                    << "\n\twidth (target matrix):    " << width
                    << "\n\theight (target matrix):   " << height
                    );

                if (exp.destructively_aliases(m) == false)
                {
                    matrix_assign(*this, subm(m,top,left,height,width)+exp);
                }
                else
                {
                    // make a temporary copy of the matrix we are going to assign to m to
                    // avoid aliasing issues during the copy
                    this->operator+=(tmp(exp));
                }

                return *this;
            }

            template <typename EXP>
            assignable_sub_matrix& operator-= (
                const matrix_exp<EXP>& exp
            )
            {
                DLIB_ASSERT( exp.nr() == height && exp.nc() == width,
                    "\tassignable_matrix_expression set_subm()"
                    << "\n\tYou have tried to assign to this object using a matrix that isn't the right size"
                    << "\n\texp.nr() (source matrix): " << exp.nr()
                    << "\n\texp.nc() (source matrix): " << exp.nc()
                    << "\n\twidth (target matrix):    " << width
                    << "\n\theight (target matrix):   " << height
                    );

                if (exp.destructively_aliases(m) == false)
                {
                    matrix_assign(*this, subm(m,top,left,height,width)-exp);
                }
                else
                {
                    // make a temporary copy of the matrix we are going to assign to m to
                    // avoid aliasing issues during the copy
                    this->operator-=(tmp(exp));
                }

                return *this;
            }

            assignable_sub_matrix& operator= (
                const T& value
            )
            {
                const long bottom = top+height-1;
                const long right = left+width-1;
                for (long r = top; r <= bottom; ++r)
                {
                    for (long c = left; c <= right; ++c)
                    {
                        m(r,c) = value;
                    }
                }

                return *this;
            }

            assignable_sub_matrix& operator+= (
                const T& value
            )
            {
                const long bottom = top+height-1;
                const long right = left+width-1;
                for (long r = top; r <= bottom; ++r)
                {
                    for (long c = left; c <= right; ++c)
                    {
                        m(r,c) += value;
                    }
                }

                return *this;
            }

            assignable_sub_matrix& operator-= (
                const T& value
            )
            {
                const long bottom = top+height-1;
                const long right = left+width-1;
                for (long r = top; r <= bottom; ++r)
                {
                    for (long c = left; c <= right; ++c)
                    {
                        m(r,c) -= value;
                    }
                }

                return *this;
            }

            matrix<T,NR,NC,mm,l>& m;
            const long left, top, width, height;
        };

        template <typename T, long NR, long NC, typename mm, typename l>
        assignable_sub_matrix<T,NR,NC,mm,l> set_subm (
            matrix<T,NR,NC,mm,l>& m,
            const rectangle& rect
        )
        {
            DLIB_ASSERT(get_rect(m).contains(rect) == true,
                "\tassignable_matrix_expression set_subm(matrix& m, const rectangle& rect)"
                << "\n\tYou have specified invalid sub matrix dimensions"
                << "\n\tm.nr(): " << m.nr()
                << "\n\tm.nc(): " << m.nc()
                << "\n\trect.left():   " << rect.left()
                << "\n\trect.top():    " << rect.top()
                << "\n\trect.right():  " << rect.right()
                << "\n\trect.bottom(): " << rect.bottom()
                );

            return assignable_sub_matrix<T,NR,NC,mm,l>(m,rect.top(), rect.left(), rect.height(), rect.width());
        }

        template <typename T, long NR, long NC, typename mm, typename l>
        assignable_sub_matrix<T,NR,NC,mm,l> set_subm (
            matrix<T,NR,NC,mm,l>& m,
            long r,
            long c,
            long nr,
            long nc
        )
        {
            DLIB_ASSERT(r >= 0 && c >= 0 && nr >= 0 && nc >= 0 && r+nr <= m.nr() && c+nc <= m.nc(),
                        "\tassignable_matrix_expression set_subm(matrix& m, r, c, nr, nc)"
                        << "\n\tYou have specified invalid sub matrix dimensions"
                        << "\n\tm.nr(): " << m.nr()
                        << "\n\tm.nc(): " << m.nc()
                        << "\n\tr:      " << r
                        << "\n\tc:      " << c
                        << "\n\tnr:     " << nr
                        << "\n\tnc:     " << nc
            );

            return assignable_sub_matrix<T,NR,NC,mm,l>(m,r,c, nr, nc);
        }

    // ----------------------------------------------------------------------------------------

        template <typename T, long NR, long NC, typename mm, typename l, typename EXPr, typename EXPc>
        class assignable_sub_range_matrix
        {
        public:
            typedef T type;
            typedef l layout_type;
            typedef matrix<T,NR,NC,mm,l> matrix_type;

            assignable_sub_range_matrix(
                matrix<T,NR,NC,mm,l>& m_,
                const EXPr& rows_,
                const EXPc& cols_
            ) : m(m_), rows(rows_), cols(cols_) {}

            T& operator() (
                long r,
                long c
            )
            {
                return m(rows(r),cols(c));
            }

            long nr() const { return rows.size(); }
            long nc() const { return cols.size(); }

            template <typename EXP>
            assignable_sub_range_matrix& operator= (
                const matrix_exp<EXP>& exp
            )
            {
                DLIB_ASSERT( exp.nr() == rows.size() && exp.nc() == cols.size(),
                    "\tassignable_matrix_expression set_subm(matrix& m, const matrix_exp rows, const matrix_exp cols)"
                    << "\n\tYou have tried to assign to this object using a matrix that isn't the right size"
                    << "\n\texp.nr() (source matrix): " << exp.nr()
                    << "\n\texp.nc() (source matrix): " << exp.nc()
                    << "\n\trows.size() (target matrix):  " << rows.size()
                    << "\n\tcols.size() (target matrix):  " << cols.size()
                    );

                if (exp.destructively_aliases(m) == false)
                {
                    matrix_assign(*this, exp);
                }
                else
                {
                    // make a temporary copy of the matrix we are going to assign to m to
                    // avoid aliasing issues during the copy
                    this->operator=(tmp(exp));
                }

                return *this;
            }

            template <typename EXP>
            assignable_sub_range_matrix& operator+= (
                const matrix_exp<EXP>& exp
            )
            {
                DLIB_ASSERT( exp.nr() == rows.size() && exp.nc() == cols.size(),
                    "\tassignable_matrix_expression set_subm(matrix& m, const matrix_exp rows, const matrix_exp cols)"
                    << "\n\tYou have tried to assign to this object using a matrix that isn't the right size"
                    << "\n\texp.nr() (source matrix): " << exp.nr()
                    << "\n\texp.nc() (source matrix): " << exp.nc()
                    << "\n\trows.size() (target matrix):  " << rows.size()
                    << "\n\tcols.size() (target matrix):  " << cols.size()
                    );

                if (exp.destructively_aliases(m) == false)
                {
                    matrix_assign(*this, subm(m,rows,cols)+exp);
                }
                else
                {
                    // make a temporary copy of the matrix we are going to assign to m to
                    // avoid aliasing issues during the copy
                    this->operator+=(tmp(exp));
                }

                return *this;
            }

            template <typename EXP>
            assignable_sub_range_matrix& operator-= (
                const matrix_exp<EXP>& exp
            )
            {
                DLIB_ASSERT( exp.nr() == rows.size() && exp.nc() == cols.size(),
                    "\tassignable_matrix_expression set_subm(matrix& m, const matrix_exp rows, const matrix_exp cols)"
                    << "\n\tYou have tried to assign to this object using a matrix that isn't the right size"
                    << "\n\texp.nr() (source matrix): " << exp.nr()
                    << "\n\texp.nc() (source matrix): " << exp.nc()
                    << "\n\trows.size() (target matrix):  " << rows.size()
                    << "\n\tcols.size() (target matrix):  " << cols.size()
                    );

                if (exp.destructively_aliases(m) == false)
                {
                    matrix_assign(*this, subm(m,rows,cols)-exp);
                }
                else
                {
                    // make a temporary copy of the matrix we are going to assign to m to
                    // avoid aliasing issues during the copy
                    this->operator-=(tmp(exp));
                }

                return *this;
            }

            assignable_sub_range_matrix& operator= (
                const T& value
            )
            {
                for (long r = 0; r < rows.size(); ++r)
                {
                    for (long c = 0; c < cols.size(); ++c)
                    {
                        m(rows(r),cols(c)) = value;
                    }
                }

                return *this;
            }

            assignable_sub_range_matrix& operator+= (
                const T& value
            )
            {
                for (long r = 0; r < rows.size(); ++r)
                {
                    for (long c = 0; c < cols.size(); ++c)
                    {
                        m(rows(r),cols(c)) += value;
                    }
                }

                return *this;
            }

            assignable_sub_range_matrix& operator-= (
                const T& value
            )
            {
                for (long r = 0; r < rows.size(); ++r)
                {
                    for (long c = 0; c < cols.size(); ++c)
                    {
                        m(rows(r),cols(c)) -= value;
                    }
                }

                return *this;
            }

        private:

            matrix<T,NR,NC,mm,l>& m;
            const EXPr rows;
            const EXPc cols;
        };

        template <typename T, long NR, long NC, typename mm, typename l, typename EXPr, typename EXPc>
        assignable_sub_range_matrix<T,NR,NC,mm,l,EXPr,EXPc > set_subm (
            matrix<T,NR,NC,mm,l>& m,
            const matrix_exp<EXPr>& rows,
            const matrix_exp<EXPc>& cols
        )
        {
            DLIB_ASSERT(0 <= min(rows) && max(rows) < m.nr() && 0 <= min(cols) && max(cols) < m.nc() &&
                        (rows.nr() == 1 || rows.nc() == 1) && (cols.nr() == 1 || cols.nc() == 1),
                "\tassignable_matrix_expression set_subm(matrix& m, const matrix_exp& rows, const matrix_exp& cols)"
                << "\n\tYou have specified invalid sub matrix dimensions"
                << "\n\tm.nr():     " << m.nr()
                << "\n\tm.nc():     " << m.nc()
                << "\n\tmin(rows):  " << min(rows)
                << "\n\tmax(rows):  " << max(rows)
                << "\n\tmin(cols):  " << min(cols)
                << "\n\tmax(cols):  " << max(cols)
                << "\n\trows.nr():  " << rows.nr()
                << "\n\trows.nc():  " << rows.nc()
                << "\n\tcols.nr():  " << cols.nr()
                << "\n\tcols.nc():  " << cols.nc()
                );

            return assignable_sub_range_matrix<T,NR,NC,mm,l,EXPr,EXPc >(m,rows.ref(),cols.ref());
        }

    // ----------------------------------------------------------------------------------------

        template <typename T, long NR, long NC, typename mm, typename l, typename EXPr>
        assignable_sub_range_matrix<T,NR,NC,mm,l,EXPr,matrix_range_exp<long> > set_rowm (
            matrix<T,NR,NC,mm,l>& m,
            const matrix_exp<EXPr>& rows
        )
        {
            DLIB_ASSERT(0 <= min(rows) && max(rows) < m.nr() && (rows.nr() == 1 || rows.nc() == 1),
                "\tassignable_matrix_expression set_rowm(matrix& m, const matrix_exp& rows)"
                << "\n\tYou have specified invalid sub matrix dimensions"
                << "\n\tm.nr():     " << m.nr()
                << "\n\tm.nc():     " << m.nc()
                << "\n\tmin(rows):  " << min(rows)
                << "\n\tmax(rows):  " << max(rows)
                << "\n\trows.nr():  " << rows.nr()
                << "\n\trows.nc():  " << rows.nc()
                );

            return assignable_sub_range_matrix<T,NR,NC,mm,l,EXPr,matrix_range_exp<long> >(m,rows.ref(),range(0,m.nc()-1));
        }

    // ----------------------------------------------------------------------------------------

        template <typename T, long NR, long NC, typename mm, typename l, typename EXPc>
        assignable_sub_range_matrix<T,NR,NC,mm,l,matrix_range_exp<long>,EXPc > set_colm (
            matrix<T,NR,NC,mm,l>& m,
            const matrix_exp<EXPc>& cols
        )
        {
            DLIB_ASSERT(0 <= min(cols) && max(cols) < m.nc() && (cols.nr() == 1 || cols.nc() == 1),
                "\tassignable_matrix_expression set_colm(matrix& m, const matrix_exp& cols)"
                << "\n\tYou have specified invalid sub matrix dimensions"
                << "\n\tm.nr():     " << m.nr()
                << "\n\tm.nc():     " << m.nc()
                << "\n\tmin(cols):  " << min(cols)
                << "\n\tmax(cols):  " << max(cols)
                << "\n\tcols.nr():  " << cols.nr()
                << "\n\tcols.nc():  " << cols.nc()
                );

            return assignable_sub_range_matrix<T,NR,NC,mm,l,matrix_range_exp<long>,EXPc >(m,range(0,m.nr()-1),cols.ref());
        }

    // ----------------------------------------------------------------------------------------

        template <typename T, long NR, long NC, typename mm, typename l>
        class assignable_col_matrix
        {
        public:
            typedef T type;
            typedef l layout_type;
            typedef matrix<T,NR,NC,mm,l> matrix_type;

            assignable_col_matrix(
                matrix<T,NR,NC,mm,l>& m_,
                const long col_
            ) : m(m_), col(col_) {}

            T& operator() (
                long r,
                long
            )
            {
                return m(r,col);
            }

            const T& operator() (
                long r,
                long
            ) const
            {
                return m(r,col);
            }

            long nr() const { return m.nr(); }
            long nc() const { return 1; }

            template <typename EXP>
            assignable_col_matrix& operator= (
                const matrix_exp<EXP>& exp
            )
            {
                DLIB_ASSERT( exp.nc() == 1 && exp.nr() == m.nr(),
                    "\tassignable_matrix_expression set_colm()"
                    << "\n\tYou have tried to assign to this object using a matrix that isn't the right size"
                    << "\n\texp.nr() (source matrix): " << exp.nr()
                    << "\n\texp.nc() (source matrix): " << exp.nc()
                    << "\n\tm.nr() (target matrix):   " << m.nr()
                    );

                if (exp.destructively_aliases(m) == false)
                {
                    matrix_assign(*this, exp);
                }
                else
                {
                    // make a temporary copy of the matrix we are going to assign to m to
                    // avoid aliasing issues during the copy
                    this->operator=(tmp(exp));
                }

                return *this;
            }

            template <typename EXP>
            assignable_col_matrix& operator+= (
                const matrix_exp<EXP>& exp
            )
            {
                DLIB_ASSERT( exp.nc() == 1 && exp.nr() == m.nr(),
                    "\tassignable_matrix_expression set_colm()"
                    << "\n\tYou have tried to assign to this object using a matrix that isn't the right size"
                    << "\n\texp.nr() (source matrix): " << exp.nr()
                    << "\n\texp.nc() (source matrix): " << exp.nc()
                    << "\n\tm.nr() (target matrix):   " << m.nr()
                    );

                if (exp.destructively_aliases(m) == false)
                {
                    matrix_assign(*this, colm(m,col)+exp);
                }
                else
                {
                    // make a temporary copy of the matrix we are going to assign to m to
                    // avoid aliasing issues during the copy
                    this->operator+=(tmp(exp));
                }

                return *this;
            }

            template <typename EXP>
            assignable_col_matrix& operator-= (
                const matrix_exp<EXP>& exp
            )
            {
                DLIB_ASSERT( exp.nc() == 1 && exp.nr() == m.nr(),
                    "\tassignable_matrix_expression set_colm()"
                    << "\n\tYou have tried to assign to this object using a matrix that isn't the right size"
                    << "\n\texp.nr() (source matrix): " << exp.nr()
                    << "\n\texp.nc() (source matrix): " << exp.nc()
                    << "\n\tm.nr() (target matrix):   " << m.nr()
                    );

                if (exp.destructively_aliases(m) == false)
                {
                    matrix_assign(*this, colm(m,col)-exp);
                }
                else
                {
                    // make a temporary copy of the matrix we are going to assign to m to
                    // avoid aliasing issues during the copy
                    this->operator-=(tmp(exp));
                }

                return *this;
            }

            assignable_col_matrix& operator= (
                const T& value
            )
            {
                for (long i = 0; i < m.nr(); ++i)
                {
                    m(i,col) = value;
                }

                return *this;
            }

            assignable_col_matrix& operator+= (
                const T& value
            )
            {
                for (long i = 0; i < m.nr(); ++i)
                {
                    m(i,col) += value;
                }

                return *this;
            }

            assignable_col_matrix& operator-= (
                const T& value
            )
            {
                for (long i = 0; i < m.nr(); ++i)
                {
                    m(i,col) -= value;
                }

                return *this;
            }

            matrix<T,NR,NC,mm,l>& m;
            const long col;
        };

        template <typename T, long NR, long NC, typename mm, typename l>
        assignable_col_matrix<T,NR,NC,mm,l> set_colm (
            matrix<T,NR,NC,mm,l>& m,
            const long col
        )
        {
            DLIB_ASSERT(col >= 0 && col < m.nc(),
                "\tassignable_matrix_expression set_colm(matrix& m, col)"
                << "\n\tYou have specified invalid sub matrix dimensions"
                << "\n\tm.nr(): " << m.nr()
                << "\n\tm.nc(): " << m.nc()
                << "\n\tcol:    " << col
                );

            return assignable_col_matrix<T,NR,NC,mm,l>(m,col);
        }

    // ----------------------------------------------------------------------------------------

        template <typename T, long NR, long NC, typename mm, typename l>
        class assignable_row_matrix
        {
        public:
            typedef T type;
            typedef l layout_type;
            typedef matrix<T,NR,NC,mm,l> matrix_type;

            assignable_row_matrix(
                matrix<T,NR,NC,mm,l>& m_,
                const long row_
            ) : m(m_), row(row_) {}

            T& operator() (
                long ,
                long c
            )
            {
                return m(row,c);
            }

            const T& operator() (
                long ,
                long c
            ) const
            {
                return m(row,c);
            }

            long nr() const { return 1; }
            long nc() const { return m.nc(); }

            template <typename EXP>
            assignable_row_matrix& operator= (
                const matrix_exp<EXP>& exp
            )
            {
                DLIB_ASSERT( exp.nr() == 1 && exp.nc() == m.nc(),
                    "\tassignable_matrix_expression set_rowm()"
                    << "\n\tYou have tried to assign to this object using a matrix that isn't the right size"
                    << "\n\texp.nr() (source matrix): " << exp.nr()
                    << "\n\texp.nc() (source matrix): " << exp.nc()
                    << "\n\tm.nc() (target matrix):   " << m.nc()
                    );

                if (exp.destructively_aliases(m) == false)
                {
                    matrix_assign(*this, exp);
                }
                else
                {
                    // make a temporary copy of the matrix we are going to assign to m to
                    // avoid aliasing issues during the copy
                    this->operator=(tmp(exp));
                }

                return *this;
            }

            template <typename EXP>
            assignable_row_matrix& operator+= (
                const matrix_exp<EXP>& exp
            )
            {
                DLIB_ASSERT( exp.nr() == 1 && exp.nc() == m.nc(),
                    "\tassignable_matrix_expression set_rowm()"
                    << "\n\tYou have tried to assign to this object using a matrix that isn't the right size"
                    << "\n\texp.nr() (source matrix): " << exp.nr()
                    << "\n\texp.nc() (source matrix): " << exp.nc()
                    << "\n\tm.nc() (target matrix):   " << m.nc()
                    );

                if (exp.destructively_aliases(m) == false)
                {
                    matrix_assign(*this, rowm(m,row)+exp);
                }
                else
                {
                    // make a temporary copy of the matrix we are going to assign to m to
                    // avoid aliasing issues during the copy
                    this->operator+=(tmp(exp));
                }

                return *this;
            }

            template <typename EXP>
            assignable_row_matrix& operator-= (
                const matrix_exp<EXP>& exp
            )
            {
                DLIB_ASSERT( exp.nr() == 1 && exp.nc() == m.nc(),
                    "\tassignable_matrix_expression set_rowm()"
                    << "\n\tYou have tried to assign to this object using a matrix that isn't the right size"
                    << "\n\texp.nr() (source matrix): " << exp.nr()
                    << "\n\texp.nc() (source matrix): " << exp.nc()
                    << "\n\tm.nc() (target matrix):   " << m.nc()
                    );

                if (exp.destructively_aliases(m) == false)
                {
                    matrix_assign(*this, rowm(m,row)-exp);
                }
                else
                {
                    // make a temporary copy of the matrix we are going to assign to m to
                    // avoid aliasing issues during the copy
                    this->operator-=(tmp(exp));
                }

                return *this;
            }

            assignable_row_matrix& operator= (
                const T& value
            )
            {
                for (long i = 0; i < m.nc(); ++i)
                {
                    m(row,i) = value;
                }

                return *this;
            }

            assignable_row_matrix& operator+= (
                const T& value
            )
            {
                for (long i = 0; i < m.nc(); ++i)
                {
                    m(row,i) += value;
                }

                return *this;
            }

            assignable_row_matrix& operator-= (
                const T& value
            )
            {
                for (long i = 0; i < m.nc(); ++i)
                {
                    m(row,i) -= value;
                }

                return *this;
            }

            matrix<T,NR,NC,mm,l>& m;
            const long row;
        };

        template <typename T, long NR, long NC, typename mm, typename l>
        assignable_row_matrix<T,NR,NC,mm,l> set_rowm (
            matrix<T,NR,NC,mm,l>& m,
            const long row
        )
        {
            DLIB_ASSERT(row >= 0 && row < m.nr(),
                "\tassignable_matrix_expression set_rowm(matrix& m, row)"
                << "\n\tYou have specified invalid sub matrix dimensions"
                << "\n\tm.nr(): " << m.nr()
                << "\n\tm.nc(): " << m.nc()
                << "\n\trow:    " << row
                );

            return assignable_row_matrix<T,NR,NC,mm,l>(m,row);
        }

    // ----------------------------------------------------------------------------------------

    }

    #endif // DLIB_MATRIx_SUBEXP_