diagonal_reference.hpp

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//=======================================================================
// Copyright (c) 2014-2023 Baptiste Wicht
// Distributed under the terms of the MIT License.
// (See accompanying file LICENSE or copy at
//  http://opensource.org/licenses/MIT)
//=======================================================================

#pragma once

namespace etl {

namespace diagonal_detail {

template <typename M>
struct diagonal_reference {
    using matrix_type              = M;                                
    using value_type               = typename matrix_type::value_type; 
    using raw_pointer_type         = value_type*;                      
    using raw_reference_type       = value_type&;                      
    using const_raw_reference_type = std::add_const_t<value_type>&;    
    using expr_t                   = M;                                

    matrix_type& matrix; 
    size_t i;            
    size_t j;            
    value_type& value;   

    diagonal_reference(matrix_type& matrix, size_t i, size_t j) : matrix(matrix), i(i), j(j), value(matrix(i, j)) {
        //Nothing else to init
    }

    diagonal_reference& operator=(const value_type& rhs) {
        if (i == j || rhs == value_type(0)) {
            value = rhs;
        } else {
            throw diagonal_exception();
        }

        return *this;
    }

    diagonal_reference& operator+=(value_type rhs) {
        if (i == j || rhs == value_type(0)) {
            value += rhs;
        } else {
            throw diagonal_exception();
        }

        return *this;
    }

    diagonal_reference& operator-=(value_type rhs) {
        if (i == j || rhs == value_type(0)) {
            value -= rhs;
        } else {
            throw diagonal_exception();
        }

        return *this;
    }

    diagonal_reference& operator*=(value_type rhs) {
        if (i == j || rhs == value_type(1)) {
            value *= rhs;
        } else {
            throw diagonal_exception();
        }

        return *this;
    }

    diagonal_reference& operator/=(value_type rhs) {
        if (i == j || rhs == value_type(1)) {
            value /= rhs;
        } else {
            throw diagonal_exception();
        }

        return *this;
    }

    diagonal_reference& operator%=(value_type rhs) {
        if (i == j || (value % rhs) == value_type(0)) {
            value %= rhs;
        } else {
            throw diagonal_exception();
        }

        return *this;
    }

    operator const_raw_reference_type&() const {
        return value;
    }
};

} //end of namespace diagonal_detail

} //end of namespace etl