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Archivo de encabezado de la biblioteca estándar <linalg> (C++26)

namespace std::linalg {

// etiquetas de orden de almacenamiento
struct column_major_t;
inline constexpr column_major_t column_major;
struct row_major_t;
inline constexpr row_major_t row_major;

// etiquetas de triángulo
struct upper_triangle_t;
inline constexpr upper_triangle_t upper_triangle;
struct lower_triangle_t;
inline constexpr lower_triangle_t lower_triangle;

// etiquetas diagonales
struct implicit_unit_diagonal_t;
inline constexpr implicit_unit_diagonal_t implicit_unit_diagonal;
struct explicit_diagonal_t;
inline constexpr explicit_diagonal_t explicit_diagonal;

// plantilla de clase layout_blas_packed
template<class Triangle, class StorageOrder>
class layout_blas_packed;

// rasgos y conceptos de solo exposición
template<class T>
struct __is_mdspan; // solo exposición

template<class T>
concept __in_vector = /* véase descripción */; // solo exposición

template<class T>
concept __out_vector = /* véase descripción */; // solo exposición

template<class T>
concept __inout_vector = /* véase descripción */; // solo exposición

template<class T>
concept __in_matrix = /* véase descripción */; // solo exposición

template<class T>
concept __out_matrix = /* véase descripción */; // solo exposición

template<class T>
concept __inout_matrix = /* véase descripción */; // solo exposición

template<class T>
concept __possibly_packed_inout_matrix = /* véase descripción */; // solo exposición

template<class T>
concept __in_object = /* véase descripción */; // solo exposición

template<class T>
concept __out_object = /* véase descripción */; // solo exposición

template<class T>
concept __inout_object = /* véase descripción */; // solo exposición

// transformación in situ a escala
template<class ScalingFactor, class Accessor>
class scaled_accessor;

template<class ScalingFactor,
         class ElementType, class Extents, class Layout, class Accessor>
constexpr auto scaled(ScalingFactor scaling_factor,
                      mdspan<ElementType, Extents, Layout, Accessor> x);

// transformación in situ conjugada
template<class Accessor>
class conjugated_accessor;

template<class ElementType, class Extents, class Layout, class Accessor>
constexpr auto conjugated(mdspan<ElementType, Extents, Layout, Accessor> a);

// transformación in situ transpuesta
template<class Layout>
class layout_transpose;

template<class ElementType, class Extents, class Layout, class Accessor>
constexpr auto transposed(mdspan<ElementType, Extents, Layout, Accessor> a);

// transformación in situ conjugada transpuesta
template<class ElementType, class Extents, class Layout, class Accessor>
constexpr auto conjugate_transposed(mdspan<ElementType, Extents, Layout, Accessor> a);

// algoritmos
// calcular rotación Givens

template<class Real>
struct setup_givens_rotation_result {
  Real c;
  Real s;
  Real r;
};

template<class Real>
struct setup_givens_rotation_result<complex<Real>> {
  Real c;
  complex<Real> s;
  complex<Real> r;
};

template<class Real>
setup_givens_rotation_result<Real> setup_givens_rotation(Real a, Real b) noexcept;

template<class Real>
setup_givens_rotation_result<complex<Real>>
setup_givens_rotation(complex<Real> a, complex<Real> b) noexcept;

// aplicar rotación Givens calculada
template<__inout_vector InOutVec1, __inout_vector InOutVec2, class Real>
void apply_givens_rotation(InOutVec1 x, InOutVec2 y, Real c, Real s);

template<class ExecutionPolicy,
         __inout_vector InOutVec1, __inout_vector InOutVec2, class Real>
void apply_givens_rotation(ExecutionPolicy&& exec,
                           InOutVec1 x, InOutVec2 y, Real c, Real s);

template<__inout_vector InOutVec1, __inout_vector InOutVec2, class Real>
void apply_givens_rotation(InOutVec1 x, InOutVec2 y, Real c, complex<Real> s);

template<class ExecutionPolicy,
         __inout_vector InOutVec1, __inout_vector InOutVec2, class Real>
void apply_givens_rotation(ExecutionPolicy&& exec,
                           InOutVec1 x, InOutVec2 y, Real c, complex<Real> s);

// intercambiar elementos
template<__inout_object InOutObj1, __inout_object InOutObj2>
void swap_elements(InOutObj1 x, InOutObj2 y);

template<class ExecutionPolicy, __inout_object InOutObj1, __inout_object InOutObj2>
void swap_elements(ExecutionPolicy&& exec, InOutObj1 x, InOutObj2 y);

// multiplicar elementos por escalar
template<class Scalar, __inout_object InOutObj>
void scale(Scalar alpha, InOutObj x);

template<class ExecutionPolicy, class Scalar, __inout_object InOutObj>
void scale(ExecutionPolicy&& exec, Scalar alpha, InOutObj x);

// copiar elementos
template<__in_object InObj, __out_object OutObj>
void copy(InObj x, OutObj y);

template<class ExecutionPolicy, __in_object InObj, __out_object OutObj>
void copy(ExecutionPolicy&& exec, InObj x, OutObj y);

// agregar elemento por elemento
template<__in_object InObj1, __in_object InObj2, __out_object OutObj>
void add(InObj1 x, InObj2 y, OutObj z);

template<class ExecutionPolicy,
         __in_object InObj1, __in_object InObj2, __out_object OutObj>
void add(ExecutionPolicy&& exec, InObj1 x, InObj2 y, OutObj z);

// producto escalar no conjugado de dos vectores
template<__in_vector InVec1, __in_vector InVec2, class Scalar>
Scalar dot(InVec1 v1, InVec2 v2, Scalar init);

template<class ExecutionPolicy,
         __in_vector InVec1, __in_vector InVec2, class Scalar>
Scalar dot(ExecutionPolicy&& exec, InVec1 v1, InVec2 v2, Scalar init);

template<__in_vector InVec1, __in_vector InVec2>
auto dot(InVec1 v1, InVec2 v2) -> /* véase descripción */;

template<class ExecutionPolicy, __in_vector InVec1, __in_vector InVec2>
auto dot(ExecutionPolicy&& exec, InVec1 v1, InVec2 v2) -> /* véase descripción */;

// producto escalar conjugado de dos vectores
template<__in_vector InVec1, __in_vector InVec2, class Scalar>
Scalar dotc(InVec1 v1, InVec2 v2, Scalar init);

template<class ExecutionPolicy,
         __in_vector InVec1, __in_vector InVec2, class Scalar>
Scalar dotc(ExecutionPolicy&& exec, InVec1 v1, InVec2 v2, Scalar init);

template<__in_vector InVec1, __in_vector InVec2>
auto dotc(InVec1 v1, InVec2 v2) -> /* véase descripción */;

template<class ExecutionPolicy, __in_vector InVec1, __in_vector InVec2>
auto dotc(ExecutionPolicy&& exec, InVec1 v1, InVec2 v2) -> /* véase descripción */;

// suma escalada de cuadrados de los elementos de un vector
template<class Scalar>
struct sum_of_squares_result {
  Scalar scaling_factor;
  Scalar scaled_sum_of_squares;
};

template<__in_vector InVec, class Scalar>
sum_of_squares_result<Scalar>
vector_sum_of_squares(InVec v, sum_of_squares_result<Scalar> init);

template<class ExecutionPolicy, __in_vector InVec, class Scalar>
sum_of_squares_result<Scalar>
vector_sum_of_squares(ExecutionPolicy&& exec, InVec v,
                      sum_of_squares_result<Scalar> init);

// norma euclidiana de un vector
template<__in_vector InVec, class Scalar>
Scalar vector_two_norm(InVec v, Scalar init);

template<class ExecutionPolicy, __in_vector InVec, class Scalar>
Scalar vector_two_norm(ExecutionPolicy&& exec, InVec v, Scalar init);

template<__in_vector InVec>
auto vector_two_norm(InVec v) -> /* véase descripción */;

template<class ExecutionPolicy, __in_vector InVec>
auto vector_two_norm(ExecutionPolicy&& exec, InVec v) -> /* véase descripción */;

// suma de valores absolutos de elementos vectoriales
template<__in_vector InVec, class Scalar>
Scalar vector_abs_sum(InVec v, Scalar init);
template<class ExecutionPolicy, __in_vector InVec, class Scalar>
Scalar vector_abs_sum(ExecutionPolicy&& exec, InVec v, Scalar init);

template<__in_vector InVec>
auto vector_abs_sum(InVec v) -> /* véase descripción */;

template<class ExecutionPolicy, __in_vector InVec>
auto vector_abs_sum(ExecutionPolicy&& exec, InVec v) -> /* véase descripción */;

// índice del valor absoluto máximo de los elementos de un vector
template<__in_vector InVec>
typename InVec::extents_type vector_idx_abs_max(InVec v);

template<class ExecutionPolicy, __in_vector InVec>
typename InVec::extents_type vector_idx_abs_max(ExecutionPolicy&& exec, InVec v);

// norma de Frobenius de una matriz
template<__in_matrix InMat, class Scalar>
Scalar matrix_frob_norm(InMat A, Scalar init);

template<class ExecutionPolicy, __in_matrix InMat, class Scalar>
Scalar matrix_frob_norm(ExecutionPolicy&& exec,
                        InMat A, Scalar init);

template<__in_matrix InMat>
auto matrix_frob_norm(InMat A) -> /* véase descripción */;

template<class ExecutionPolicy, __in_matrix InMat>
auto matrix_frob_norm(ExecutionPolicy&& exec, InMat A) -> /* véase descripción */;

// una norma de una matriz
template<__in_matrix InMat, class Scalar>
Scalar matrix_one_norm(InMat A, Scalar init);

template<class ExecutionPolicy, __in_matrix InMat, class Scalar>
Scalar matrix_one_norm(ExecutionPolicy&& exec,
                       InMat A, Scalar init);

template<__in_matrix InMat>
auto matrix_one_norm(InMat A) -> /* véase descripción */;

template<class ExecutionPolicy, __in_matrix InMat>
auto matrix_one_norm(ExecutionPolicy&& exec, InMat A) -> /* véase descripción */;

// norma de infinidad de una matriz
template<__in_matrix InMat, class Scalar>
Scalar matrix_inf_norm(InMat A, Scalar init);

template<class ExecutionPolicy, __in_matrix InMat, class Scalar>
Scalar matrix_inf_norm(ExecutionPolicy&& exec,
                       InMat A, Scalar init);

template<__in_matrix InMat>
auto matrix_inf_norm(InMat A) -> /* véase descripción */;

template<class ExecutionPolicy, __in_matrix InMat>
auto matrix_inf_norm(ExecutionPolicy&& exec, InMat A) -> /* véase descripción */;

// producto matriz-vector general
template<__in_matrix InMat, __in_vector InVec, __out_vector OutVec>
void matrix_vector_product(InMat A, InVec x, OutVec y);

template<class ExecutionPolicy,
         __in_matrix InMat, __in_vector InVec, __out_vector OutVec>
void matrix_vector_product(ExecutionPolicy&& exec,
                           InMat A, InVec x, OutVec y);

template<__in_matrix InMat, __in_vector InVec1,
         __in_vector InVec2, __out_vector OutVec>
void matrix_vector_product(InMat A, InVec1 x, InVec2 y, OutVec z);

template<class ExecutionPolicy,
         __in_matrix InMat, __in_vector InVec1,
         __in_vector InVec2, __out_vector OutVec>
void matrix_vector_product(ExecutionPolicy&& exec,
                           InMat A, InVec1 x, InVec2 y, OutVec z);

// producto matriz-vector simétrico
template<__in_matrix InMat, class Triangle,
         __in_vector InVec, __out_vector OutVec>
void symmetric_matrix_vector_product(InMat A, Triangle t,
                                     InVec x, OutVec y);

template<class ExecutionPolicy,
         __in_matrix InMat, class Triangle,
         __in_vector InVec, __out_vector OutVec>
void symmetric_matrix_vector_product(ExecutionPolicy&& exec,
                                     InMat A, Triangle t,
                                     InVec x, OutVec y);

template<__in_matrix InMat, class Triangle,
         __in_vector InVec1, __in_vector InVec2,
         __out_vector OutVec>
void symmetric_matrix_vector_product(InMat A, Triangle t,
                                     InVec1 x, InVec2 y, OutVec z);

template<class ExecutionPolicy,
         __in_matrix InMat, class Triangle,
         __in_vector InVec1, __in_vector InVec2,
         __out_vector OutVec>
void symmetric_matrix_vector_product(ExecutionPolicy&& exec,
                                     InMat A, Triangle t,
                                     InVec1 x, InVec2 y, OutVec z);

// producto matriz-vector hermitiana
template<__in_matrix InMat, class Triangle,
         __in_vector InVec, __out_vector OutVec>
void hermitian_matrix_vector_product(InMat A, Triangle t,
                                     InVec x, OutVec y);

template<class ExecutionPolicy,
         __in_matrix InMat, class Triangle,
         __in_vector InVec, __out_vector OutVec>
void hermitian_matrix_vector_product(ExecutionPolicy&& exec,
                                     InMat A, Triangle t,
                                     InVec x, OutVec y);

template<__in_matrix InMat, class Triangle,
         __in_vector InVec1, __in_vector InVec2,
         __out_vector OutVec>
void hermitian_matrix_vector_product(InMat A, Triangle t,
                                     InVec1 x, InVec2 y, OutVec z);

template<class ExecutionPolicy,
         __in_matrix InMat, class Triangle,
         __in_vector InVec1, __in_vector InVec2,
         __out_vector OutVec>
void hermitian_matrix_vector_product(ExecutionPolicy&& exec,
                                     InMat A, Triangle t,
                                     InVec1 x, InVec2 y, OutVec z);

// producto matriz-vector triangular
// Overwriting triangular matrix-vector product
template<__in_matrix InMat, class Triangle, class DiagonalStorage,
         __in_vector InVec, __out_vector OutVec>
void triangular_matrix_vector_product(InMat A, Triangle t, DiagonalStorage d,
                                      InVec x, OutVec y);

template<class ExecutionPolicy,
         __in_matrix InMat, class Triangle, class DiagonalStorage,
         __in_vector InVec, __out_vector OutVec>
void triangular_matrix_vector_product(ExecutionPolicy&& exec,
                                      InMat A, Triangle t, DiagonalStorage d,
                                      InVec x, OutVec y);

// producto in situ matriz-vector triangular
template<__in_matrix InMat, class Triangle, class DiagonalStorage,
         __inout_vector InOutVec>
void triangular_matrix_vector_product(InMat A, Triangle t, DiagonalStorage d,
                                      InOutVec y);

template<class ExecutionPolicy,
         __in_matrix InMat, class Triangle, class DiagonalStorage,
         __inout_vector InOutVec>
void triangular_matrix_vector_product(ExecutionPolicy&& exec,
                                      InMat A, Triangle t, DiagonalStorage d,
                                      InOutVec y);

// actualizar producto matriz-vector triangular
template<__in_matrix InMat, class Triangle, class DiagonalStorage,
         __in_vector InVec1, __in_vector InVec2,
         __out_vector OutVec>
void triangular_matrix_vector_product(InMat A, Triangle t, DiagonalStorage d,
                                      InVec1 x, InVec2 y, OutVec z);

template<class ExecutionPolicy,
         __in_matrix InMat, class Triangle, class DiagonalStorage,
         __in_vector InVec1, __in_vector InVec2,
         __out_vector OutVec>
void triangular_matrix_vector_product(ExecutionPolicy&& exec,
                                      InMat A, Triangle t, DiagonalStorage d,
                                      InVec1 x, InVec2 y, OutVec z);

// resolver un sistema lineal triangular, no in situ
template<__in_matrix InMat, class Triangle, class DiagonalStorage,
         __in_vector InVec, __out_vector OutVec, class BinaryDivideOp>
void triangular_matrix_vector_solve(InMat A, Triangle t, DiagonalStorage d,
                                    InVec b, OutVec x, BinaryDivideOp divide);

template<class ExecutionPolicy,
         __in_matrix InMat, class Triangle, class DiagonalStorage,
         __in_vector InVec, __out_vector OutVec, class BinaryDivideOp>
void triangular_matrix_vector_solve(ExecutionPolicy&& exec,
                                    InMat A, Triangle t, DiagonalStorage d,
                                    InVec b, OutVec x, BinaryDivideOp divide);

template<__in_matrix InMat, class Triangle, class DiagonalStorage,
         __in_vector InVec, __out_vector OutVec>
void triangular_matrix_vector_solve(InMat A, Triangle t, DiagonalStorage d,
                                    InVec b, OutVec x);

template<class ExecutionPolicy,
         __in_matrix InMat, class Triangle, class DiagonalStorage,
         __in_vector InVec, __out_vector OutVec>
void triangular_matrix_vector_solve(ExecutionPolicy&& exec,
                                    InMat A, Triangle t, DiagonalStorage d,
                                    InVec b, OutVec x);

// resolver un sistema lineal triangular, in situ
template<__in_matrix InMat, class Triangle, class DiagonalStorage,
         __inout_vector InOutVec, class BinaryDivideOp>
void triangular_matrix_vector_solve(InMat A, Triangle t, DiagonalStorage d,
                                    InOutVec b, BinaryDivideOp divide);

template<class ExecutionPolicy,
         __in_matrix InMat, class Triangle, class DiagonalStorage,
         __inout_vector InOutVec, class BinaryDivideOp>
void triangular_matrix_vector_solve(ExecutionPolicy&& exec,
                                    InMat A, Triangle t, DiagonalStorage d,
                                    InOutVec b, BinaryDivideOp divide);

template<__in_matrix InMat, class Triangle, class DiagonalStorage,
         __inout_vector InOutVec>
void triangular_matrix_vector_solve(InMat A, Triangle t, DiagonalStorage d,
                                    InOutVec b);

template<class ExecutionPolicy,
         __in_matrix InMat, class Triangle, class DiagonalStorage,
         __inout_vector InOutVec>
void triangular_matrix_vector_solve(ExecutionPolicy&& exec,
                                    InMat A, Triangle t, DiagonalStorage d,
                                    InOutVec b);

// actualización de matriz de rango 1 no conjugada
template<__in_vector InVec1, __in_vector InVec2, __inout_matrix InOutMat>
void matrix_rank_1_update(InVec1 x, InVec2 y, InOutMat A);

template<class ExecutionPolicy,
         __in_vector InVec1, __in_vector InVec2, __inout_matrix InOutMat>
void matrix_rank_1_update(ExecutionPolicy&& exec,
                          InVec1 x, InVec2 y, InOutMat A);

// actualización de matriz de rango 1 conjugada
template<__in_vector InVec1, __in_vector InVec2, __inout_matrix InOutMat>
void matrix_rank_1_update_c(InVec1 x, InVec2 y, InOutMat A);

template<class ExecutionPolicy, 
         __in_vector InVec1, __in_vector InVec2, __inout_matrix InOutMat>
void matrix_rank_1_update_c(ExecutionPolicy&& exec,
                            InVec1 x, InVec2 y, InOutMat A);

// actualización de matriz simétrica de rango 1
template<__in_vector InVec, __possibly_packed_inout_matrix InOutMat,
         class Triangle>
void symmetric_matrix_rank_1_update(InVec x, InOutMat A, Triangle t);

template<class ExecutionPolicy,
         __in_vector InVec, __possibly_packed_inout_matrix InOutMat,
         class Triangle>
void symmetric_matrix_rank_1_update(ExecutionPolicy&& exec,
                                    InVec x, InOutMat A, Triangle t);

template<class Scalar, __in_vector InVec,
         __possibly_packed_inout_matrix InOutMat, class Triangle>
void symmetric_matrix_rank_1_update(Scalar alpha, InVec x, InOutMat A,
                                    Triangle t);

template<class ExecutionPolicy,
         class Scalar, __in_vector InVec,
         __possibly_packed_inout_matrix InOutMat, class Triangle>
void symmetric_matrix_rank_1_update(ExecutionPolicy&& exec,
                                    Scalar alpha, InVec x, InOutMat A,
                                    Triangle t);

// actualización de la matriz hermitiana de rango 1
template<__in_vector InVec, __possibly_packed_inout_matrix InOutMat,
         class Triangle>
void hermitian_matrix_rank_1_update(InVec x, InOutMat A, Triangle t);

template<class ExecutionPolicy,
         __in_vector InVec, __possibly_packed_inout_matrix InOutMat,
         class Triangle>
void hermitian_matrix_rank_1_update(ExecutionPolicy&& exec,
                                    InVec x, InOutMat A, Triangle t);

template<class Scalar, __in_vector InVec,
         __possibly_packed_inout_matrix InOutMat,
         class Triangle>
void hermitian_matrix_rank_1_update(Scalar alpha, InVec x, InOutMat A,
                                    Triangle t);

template<class ExecutionPolicy,
         class Scalar, __in_vector InVec,
         __possibly_packed_inout_matrix InOutMat,
         class Triangle>
void hermitian_matrix_rank_1_update(ExecutionPolicy&& exec,
                                    Scalar alpha, InVec x, InOutMat A,
                                    Triangle t);

// actualización de matriz simétrica de rango 2
template<__in_vector InVec1, __in_vector InVec2,
         __possibly_packed_inout_matrix InOutMat,
         class Triangle>
void symmetric_matrix_rank_2_update(InVec1 x, InVec2 y, InOutMat A,
                                    Triangle t);

template<class ExecutionPolicy,
         __in_vector InVec1, __in_vector InVec2,
         __possibly_packed_inout_matrix InOutMat,
         class Triangle>
void symmetric_matrix_rank_2_update(ExecutionPolicy&& exec,
                                    InVec1 x, InVec2 y, InOutMat A,
                                    Triangle t);

// actualización de la matriz hermitiana de rango 2
template<__in_vector InVec1, __in_vector InVec2,
         __possibly_packed_inout_matrix InOutMat,
         class Triangle>
void hermitian_matrix_rank_2_update(InVec1 x, InVec2 y, InOutMat A,
                                    Triangle t);

template<class ExecutionPolicy,
         __in_vector InVec1, __in_vector InVec2,
         __possibly_packed_inout_matrix InOutMat,
         class Triangle>
void hermitian_matrix_rank_2_update(ExecutionPolicy&& exec,
                                    InVec1 x, InVec2 y, InOutMat A,
                                    Triangle t);

// producto general matriz-matriz
template<__in_matrix InMat1, __in_matrix InMat2, __out_matrix OutMat>
void matrix_product(InMat1 A, InMat2 B, OutMat C);

template<class ExecutionPolicy,
         __in_matrix InMat1, __in_matrix InMat2, __out_matrix OutMat>
void matrix_product(ExecutionPolicy&& exec, InMat1 A, InMat2 B, OutMat C);

template<__in_matrix InMat1, __in_matrix InMat2, __in_matrix InMat3,
         __out_matrix OutMat>
void matrix_product(InMat1 A, InMat2 B, InMat3 E, OutMat C);

template<class ExecutionPolicy,
         __in_matrix InMat1, __in_matrix InMat2, __in_matrix InMat3,
         __out_matrix OutMat>
void matrix_product(ExecutionPolicy&& exec,
                    InMat1 A, InMat2 B, InMat3 E, OutMat C);


// producto simétrico matriz-matriz
// sobrescribir el producto izquierdo matriz-matriz simétrica
template<__in_matrix InMat1, class Triangle,
         __in_matrix InMat2, __out_matrix OutMat>
void symmetric_matrix_product(InMat1 A, Triangle t,
                              InMat2 B, OutMat C);

template<class ExecutionPolicy,
         __in_matrix InMat1, class Triangle,
         __in_matrix InMat2, __out_matrix OutMat>
void symmetric_matrix_product(ExecutionPolicy&& exec,
                              InMat1 A, Triangle t,
                              InMat2 B, OutMat C);

// sobrescribir el producto derecho matriz-matriz simétrica
template<__in_matrix InMat1, __in_matrix InMat2,
         class Triangle, __out_matrix OutMat>
void symmetric_matrix_product(InMat1 B, InMat2 A, Triangle t,
                              OutMat C);

template<class ExecutionPolicy,
         __in_matrix InMat1, __in_matrix InMat2,
         class Triangle, __out_matrix OutMat>
void symmetric_matrix_product(ExecutionPolicy&& exec,
                              InMat1 B, InMat2 A, Triangle t,
                              OutMat C);

// actualizar el producto izquierdo matriz-matriz simétrica
template<__in_matrix InMat1, class Triangle,
         __in_matrix InMat2, __in_matrix InMat3,
         __out_matrix OutMat>
void symmetric_matrix_product(InMat1 A, Triangle t,
                              InMat2 B, InMat3 E,
                              OutMat C);

template<class ExecutionPolicy,
         __in_matrix InMat1, class Triangle,
         __in_matrix InMat2, __in_matrix InMat3,
         __out_matrix OutMat>
void symmetric_matrix_product(ExecutionPolicy&& exec,
                              InMat1 A, Triangle t,
                              InMat2 B, InMat3 E,
                              OutMat C);

// actualizar el producto derecho matriz-matriz simétrica
template<__in_matrix InMat1, __in_matrix InMat2, class Triangle,
         __in_matrix InMat3, __out_matrix OutMat>
void symmetric_matrix_product(InMat1 B, InMat2 A, Triangle t,
                              InMat3 E, OutMat C);

template<class ExecutionPolicy,
         __in_matrix InMat1, __in_matrix InMat2, class Triangle,
         __in_matrix InMat3, __out_matrix OutMat>
void symmetric_matrix_product(ExecutionPolicy&& exec,
                              InMat1 B, InMat2 A, Triangle t,
                              InMat3 E, OutMat C);

// producto matriz-matrix hermitiana
// sobreescribir el producto izquierdo matriz-matrix hermitiana
template<__in_matrix InMat1, class Triangle,
         __in_matrix InMat2, __out_matrix OutMat>
void hermitian_matrix_product(InMat1 A, Triangle t,
                              InMat2 B, OutMat C);
template<class ExecutionPolicy,
         __in_matrix InMat1, class Triangle,
         __in_matrix InMat2, __out_matrix OutMat>
void hermitian_matrix_product(ExecutionPolicy&& exec,
                              InMat1 A, Triangle t,
                              InMat2 B, OutMat C);

// sobreescribir el producto derecho matriz-matrix hermitiana
template<__in_matrix InMat1, __in_matrix InMat2,
         class Triangle, __out_matrix OutMat>
void hermitian_matrix_product(InMat1 B, InMat2 A, Triangle t,
                              OutMat C);

template<class ExecutionPolicy,
         __in_matrix InMat1, __in_matrix InMat2,
         class Triangle, __out_matrix OutMat>
void hermitian_matrix_product(ExecutionPolicy&& exec,
                              InMat1 B, InMat2 A, Triangle t,
                              OutMat C);

// actualizar el producto izquierdo matriz-matrix hermitiana
template<__in_matrix InMat1, class Triangle,
         __in_matrix InMat2, __in_matrix InMat3, __out_matrix OutMat>
void hermitian_matrix_product(InMat1 A, Triangle t,
                              InMat2 B, InMat3 E, OutMat C);

template<class ExecutionPolicy,
         __in_matrix InMat1, class Triangle,
         __in_matrix InMat2, __in_matrix InMat3, __out_matrix OutMat>
void hermitian_matrix_product(ExecutionPolicy&& exec,
                              InMat1 A, Triangle t,
                              InMat2 B, InMat3 E, OutMat C);

// actualizar el producto derecho matriz-matrix hermitiana
template<__in_matrix InMat1, __in_matrix InMat2, class Triangle,
         __in_matrix InMat3, __out_matrix OutMat>
void hermitian_matrix_product(InMat1 B, InMat2 A, Triangle t,
                              InMat3 E, OutMat C);

template<class ExecutionPolicy,
         __in_matrix InMat1, __in_matrix InMat2, class Triangle,
         __in_matrix InMat3, __out_matrix OutMat>
void hermitian_matrix_product(ExecutionPolicy&& exec,
                              InMat1 B, InMat2 A, Triangle t,
                              InMat3 E, OutMat C);

// producto triangular matriz-matriz
// sobreescribir el producto izquierdo triangular matriz-matriz
template<__in_matrix InMat1, class Triangle, class DiagonalStorage,
         __in_matrix InMat2, __out_matrix OutMat>
void triangular_matrix_product(InMat1 A, Triangle t, DiagonalStorage d,
                               InMat2 B, OutMat C);

template<class ExecutionPolicy,
         __in_matrix InMat1, class Triangle, class DiagonalStorage,
         __in_matrix InMat2, __out_matrix OutMat>
void triangular_matrix_product(ExecutionPolicy&& exec,
                               InMat1 A, Triangle t, DiagonalStorage d,
                               InMat2 B, OutMat C);

template<__in_matrix InMat1, class Triangle, class DiagonalStorage,
         __inout_matrix InOutMat>
void triangular_matrix_left_product(InMat1 A, Triangle t, DiagonalStorage d,
                                    InOutMat C);

template<class ExecutionPolicy,
         __in_matrix InMat1, class Triangle, class DiagonalStorage,
         __inout_matrix InOutMat>
void triangular_matrix_left_product(ExecutionPolicy&& exec,
                                    InMat1 A, Triangle t, DiagonalStorage d,
                                    InOutMat C);

// sobreescribir el producto derecho triangular matriz-matriz
template<__in_matrix InMat1, __in_matrix InMat2,
         class Triangle, class DiagonalStorage,
         __out_matrix OutMat>
void triangular_matrix_product(InMat1 B, InMat2 A,
                               Triangle t, DiagonalStorage d,
                               OutMat C);

template<class ExecutionPolicy,
         __in_matrix InMat1, __in_matrix InMat2,
         class Triangle, class DiagonalStorage,
         __out_matrix OutMat>
void triangular_matrix_product(ExecutionPolicy&& exec,
                               InMat1 B, InMat2 A,
                               Triangle t, DiagonalStorage d,
                               OutMat C);

template<__in_matrix InMat1, class Triangle, class DiagonalStorage,
         __inout_matrix InOutMat>
void triangular_matrix_right_product(InMat1 A, Triangle t, DiagonalStorage d,
                                     InOutMat C);

template<class ExecutionPolicy,
         __in_matrix InMat1, class Triangle, class DiagonalStorage,
         __inout_matrix InOutMat>
void triangular_matrix_right_product(ExecutionPolicy&& exec,
                                     InMat1 A, Triangle t, DiagonalStorage d,
                                     InOutMat C);

// actualizar el producto izquierdo triangular matriz-matriz
template<__in_matrix InMat1, class Triangle, class DiagonalStorage,
         __in_matrix InMat2, __in_matrix InMat3,
         __out_matrix OutMat>
void triangular_matrix_product(InMat1 A, Triangle t, DiagonalStorage d,
                               InMat2 B, InMat3 E, OutMat C);

template<class ExecutionPolicy,
         __in_matrix InMat1, class Triangle, class DiagonalStorage,
         __in_matrix InMat2, __in_matrix InMat3,
         __out_matrix OutMat>
void triangular_matrix_product(ExecutionPolicy&& exec,
                               InMat1 A, Triangle t, DiagonalStorage d,
                               InMat2 B, InMat3 E, OutMat C);

// actualizar el producto drecho triangular matriz-matriz
template<__in_matrix InMat1, __in_matrix InMat2,
         class Triangle, class DiagonalStorage,
         __in_matrix InMat3, __out_matrix OutMat>
void triangular_matrix_product(InMat1 B, InMat2 A,
                               Triangle t, DiagonalStorage d,
                               InMat3 E, OutMat C);

template<class ExecutionPolicy,
         __in_matrix InMat1, __in_matrix InMat2,
         class Triangle, class DiagonalStorage,
         __in_matrix InMat3, __out_matrix OutMat>
void triangular_matrix_product(ExecutionPolicy&& exec,
                               InMat1 B, InMat2 A,
                               Triangle t, DiagonalStorage d,
                               InMat3 E, OutMat C);

// actualizar matriz simétrica de rango k
template<class Scalar, __in_matrix InMat1,
         __possibly_packed_inout_matrix InOutMat, class Triangle>
void symmetric_matrix_rank_k_update(Scalar alpha, InMat1 A, InOutMat C,
                                    Triangle t);

template<class Scalar,
         class ExecutionPolicy,
         ___in_matrix InMat1,
         __possibly_packed_inout_matrix InOutMat, class Triangle>
void symmetric_matrix_rank_k_update(ExecutionPolicy&& exec,
                                    Scalar alpha, InMat1 A, InOutMat C,
                                    Triangle t);

template<__in_matrix InMat1,
         __possibly_packed_inout_matrix InOutMat, class Triangle>
void symmetric_matrix_rank_k_update(InMat1 A, InOutMat C, Triangle t);

template<class ExecutionPolicy,
         __in_matrix InMat1,
         __possibly_packed_inout_matrix InOutMat, class Triangle>
void symmetric_matrix_rank_k_update(ExecutionPolicy&& exec,
                                    InMat1 A, InOutMat C, Triangle t);

// actualizar matriz hermitiana de rango k
template<class Scalar, __in_matrix InMat1,
         __possibly_packed_inout_matrix InOutMat, class Triangle>
void hermitian_matrix_rank_k_update(Scalar alpha, InMat1 A, InOutMat C,
                                    Triangle t);

template<class ExecutionPolicy,
         class Scalar, __in_matrix InMat1,
         __possibly_packed_inout_matrix InOutMat, class Triangle
void hermitian_matrix_rank_k_update(ExecutionPolicy&& exec,
                                    Scalar alpha, InMat1 A, InOutMat C,
                                    Triangle t);

template<__in_matrix InMat1,
         __possibly_packed_inout_matrix InOutMat, class Triangle>
void hermitian_matrix_rank_k_update(InMat1 A, InOutMat C, Triangle t);

template<class ExecutionPolicy,
         __in_matrix InMat1,
         __possibly_packed_inout_matrix InOutMat, class Triangle>
void hermitian_matrix_rank_k_update(ExecutionPolicy&& exec,
                                    InMat1 A, InOutMat C, Triangle t);

// actualizar matriz simétrica de rango 2k
template<__in_matrix InMat1, __in_matrix InMat2,
         __possibly_packed_inout_matrix InOutMat, class Triangle>
void symmetric_matrix_rank_2k_update(InMat1 A, InMat2 B, InOutMat C,
                                     Triangle t);

template<class ExecutionPolicy,
         __in_matrix InMat1, __in_matrix InMat2,
         __possibly_packed_inout_matrix InOutMat, class Triangle>
void symmetric_matrix_rank_2k_update(ExecutionPolicy&& exec,
                                     InMat1 A, InMat2 B, InOutMat C,
                                     Triangle t);

// actualizar matriz hermitiana de rango 2k
template<__in_matrix InMat1, __in_matrix InMat2,
         __possibly_packed_inout_matrix InOutMat, class Triangle>
void hermitian_matrix_rank_2k_update(InMat1 A, InMat2 B, InOutMat C,
                                     Triangle t);

template<class ExecutionPolicy,
         __in_matrix InMat1, __in_matrix InMat2,
         __possibly_packed_inout_matrix InOutMat, class Triangle>
void hermitian_matrix_rank_2k_update(ExecutionPolicy&& exec,
                                     InMat1 A, InMat2 B, InOutMat C,
                                     Triangle t);

// resolver múltiples sistemas lineales triangulares
// con matriz triangular a la izquierda
template<__in_matrix InMat1, class Triangle, class DiagonalStorage,
         __in_matrix InMat2, __out_matrix OutMat, class BinaryDivideOp>
void triangular_matrix_matrix_left_solve(InMat1 A,
                                         Triangle t, DiagonalStorage d,
                                         InMat2 B, OutMat X,
                                         BinaryDivideOp divide);

template<class ExecutionPolicy,
         __in_matrix InMat1, class Triangle, class DiagonalStorage,
         __in_matrix InMat2, __out_matrix OutMat, class BinaryDivideOp>
void triangular_matrix_matrix_left_solve(ExecutionPolicy&& exec,
                                         InMat1 A,
                                         Triangle t, DiagonalStorage d,
                                         InMat2 B, OutMat X,
                                         BinaryDivideOp divide);

template<__in_matrix InMat1, class Triangle, class DiagonalStorage,
         __inout_matrix InOutMat, class BinaryDivideOp>
void triangular_matrix_matrix_left_solve(InMat1 A, Triangle t, DiagonalStorage d,
                                         InOutMat B, BinaryDivideOp divide);

template<class ExecutionPolicy,
         __in_matrix InMat1, class Triangle, class DiagonalStorage,
         __inout_matrix InOutMat, class BinaryDivideOp>
void triangular_matrix_matrix_left_solve(ExecutionPolicy&& exec,
                                         InMat1 A, Triangle t, DiagonalStorage d,
                                         InOutMat B, BinaryDivideOp divide);

template<__in_matrix InMat1, class Triangle, class DiagonalStorage,
         __in_matrix InMat2, __out_matrix OutMat>
void triangular_matrix_matrix_left_solve(InMat1 A, Triangle t, DiagonalStorage d,
                                         InMat2 B, OutMat X);

template<class ExecutionPolicy,
         __in_matrix InMat1, class Triangle, class DiagonalStorage,
         __in_matrix InMat2, __out_matrix OutMat>
void triangular_matrix_matrix_left_solve(ExecutionPolicy&& exec,
                                         InMat1 A, Triangle t, DiagonalStorage d,
                                         InMat2 B, OutMat X);

template<__in_matrix InMat1, class Triangle, class DiagonalStorage,
         __inout_matrix InOutMat>
void triangular_matrix_matrix_left_solve(InMat1 A, Triangle t, DiagonalStorage d,
                                         InOutMat B);

template<class ExecutionPolicy,
         __in_matrix InMat1, class Triangle, class DiagonalStorage,
         __inout_matrix InOutMat>
void triangular_matrix_matrix_left_solve(ExecutionPolicy&& exec,
                                         InMat1 A, Triangle t, DiagonalStorage d,
                                         InOutMat B);

// resolver múltiples sistemas lineales triangulares
// con matriz triangular a la derecha
template<__in_matrix InMat1, class Triangle, class DiagonalStorage,
         __in_matrix InMat2, __out_matrix OutMat, class BinaryDivideOp>
void triangular_matrix_matrix_right_solve(InMat1 A, Triangle t, DiagonalStorage d,
                                          InMat2 B, OutMat X, BinaryDivideOp divide);

template<class ExecutionPolicy,
         __in_matrix InMat1, class Triangle, class DiagonalStorage,
         __in_matrix InMat2, __out_matrix OutMat, class BinaryDivideOp>
void triangular_matrix_matrix_right_solve(ExecutionPolicy&& exec,
                                          InMat1 A, Triangle t, DiagonalStorage d,
                                          InMat2 B, OutMat X, BinaryDivideOp divide);

template<__in_matrix InMat1, class Triangle, class DiagonalStorage,
         __inout_matrix InOutMat, class BinaryDivideOp>
void triangular_matrix_matrix_right_solve(InMat1 A, Triangle t, DiagonalStorage d,
                                          InOutMat B, BinaryDivideOp divide);

template<class ExecutionPolicy,
         __in_matrix InMat1, class Triangle, class DiagonalStorage,
         __inout_matrix InOutMat, class BinaryDivideOp>
void triangular_matrix_matrix_right_solve(ExecutionPolicy&& exec,
                                          InMat1 A, Triangle t, DiagonalStorage d,
                                          InOutMat B, BinaryDivideOp divide));

template<__in_matrix InMat1, class Triangle, class DiagonalStorage,
         __in_matrix InMat2, __out_matrix OutMat>
void triangular_matrix_matrix_right_solve(InMat1 A, Triangle t, DiagonalStorage d,
                                          InMat2 B, OutMat X);

template<class ExecutionPolicy,
         __in_matrix InMat1, class Triangle, class DiagonalStorage,
         __in_matrix InMat2, __out_matrix OutMat>
void triangular_matrix_matrix_right_solve(ExecutionPolicy&& exec,
                                          InMat1 A, Triangle t, DiagonalStorage d,
                                          InMat2 B, OutMat X);

template<__in_matrix InMat1, class Triangle, class DiagonalStorage,
         __inout_matrix InOutMat>
void triangular_matrix_matrix_right_solve(InMat1 A, Triangle t, DiagonalStorage d,
                                          InOutMat B);

template<class ExecutionPolicy,
         __in_matrix InMat1, class Triangle, class DiagonalStorage,
         __inout_matrix InOutMat>
void triangular_matrix_matrix_right_solve(ExecutionPolicy&& exec,
                                          InMat1 A, Triangle t, DiagonalStorage d,
                                          InOutMat B);
}

namespace std::linalg {
  struct column_major_t {
    explicit column_major_t() = default;
  };
  inline constexpr column_major_t column_major = { };

  struct row_major_t {
    explicit row_major_t() = default;
  };
  inline constexpr row_major_t row_major = { };

  struct upper_triangle_t {
    explicit upper_triangle_t() = default;
  };
  inline constexpr upper_triangle_t upper_triangle = { };

  struct lower_triangle_t {
    explicit lower_triangle_t() = default;
  };
  inline constexpr lower_triangle_t lower_triangle = { };

  struct implicit_unit_diagonal_t {
    explicit implicit_unit_diagonal_t() = default;
  };
  inline constexpr implicit_unit_diagonal_t implicit_unit_diagonal = { };

  struct explicit_diagonal_t {
    explicit explicit_diagonal_t() = default;
  };
  inline constexpr explicit_diagonal_t explicit_diagonal = { };
}

namespace std::linalg {
  template<class Triangle, class StorageOrder>
  class layout_blas_packed {
   public:
    using triangle_type = Triangle;
    using storage_order_type = StorageOrder;

    template<class Extents>
    struct mapping {
     public:
      using extents_type = Extents;
      using index_type = typename extents_type::index_type;
      using size_type = typename extents_type::size_type;
      using rank_type = typename extents_type::rank_type;
      using layout_type = layout_blas_packed<Triangle, StorageOrder>;

     private:
      Extents __the_extents{}; // solo exposición

     public:
      constexpr mapping() noexcept = default;
      constexpr mapping(const mapping&) noexcept = default;
      constexpr mapping(const extents_type& e) noexcept;
      template<class OtherExtents>
      constexpr explicit(!is_convertible_v<OtherExtents, extents_type>)
      mapping(const mapping<OtherExtents>& other) noexcept;

      constexpr mapping& operator=(const mapping&) noexcept = default;

      constexpr extents_type extents() const noexcept { return __the_extents; }

      constexpr size_type required_span_size() const noexcept;

      template<class Index0, class Index1>
      constexpr index_type operator() (Index0 ind0, Index1 ind1) const noexcept;

      static constexpr bool is_always_unique() {
        return (extents_type::static_extent(0) != dynamic_extent &&
                extents_type::static_extent(0) < 2) ||
               (extents_type::static_extent(1) != dynamic_extent &&
                extents_type::static_extent(1) < 2);
      }
      static constexpr bool is_always_exhaustive() { return true; }
      static constexpr bool is_always_strided() {
        return is_always_unique();
      }

      constexpr bool is_unique() const noexcept {
        return __the_extents.extent(0) < 2;
      }
      constexpr bool is_exhaustive() const noexcept { return true; }
      constexpr bool is_strided() const noexcept {
        return __the_extents.extent(0) < 2;
      }

      constexpr index_type stride(rank_type) const noexcept;

      template<class OtherExtents>
      friend constexpr bool
      operator==(const mapping&, const mapping<OtherExtents>&) noexcept;
      
    };
  };
}

namespace std::linalg {
  template<class ScalingFactor, class NestedAccessor>
  class scaled_accessor {
   public:
    using element_type = 
      add_const_t<decltype(declval<ScalingFactor>() * 
                           declval<NestedAccessor::element_type>())>;
    using reference = remove_const_t<element_type>;
    using data_handle_type = NestedAccessor::data_handle_type;
    using offset_policy = scaled_accessor<ScalingFactor, NestedAccessor::offset_policy>;

    constexpr scaled_accessor() = default;
    template<class OtherNestedAccessor>
      explicit(!is_convertible_v<OtherNestedAccessor, NestedAccessor>)
    constexpr scaled_accessor(const scaled_accessor<ScalingFactor, OtherNestedAccessor>&);
    constexpr scaled_accessor(const ScalingFactor& s, const Accessor& a);

    constexpr reference access(data_handle_type p, size_t i) const noexcept;
    constexpr 
      offset_policy::data_handle_type offset(data_handle_type p, size_t i) const noexcept;

    constexpr const ScalingFactor& scaling_factor() const noexcept 
      { return __scaling_factor; } 
    constexpr const NestedAccessor& nested_accessor() const noexcept
      { return __nested_accessor; }

   private:
    ScalingFactor __scaling_factor; // solo exposición
    NestedAccessor __nested_accessor; // solo exposición
  };
}

namespace std::linalg {
  template<class NestedAccessor>
  class conjugated_accessor {
   private:
    NestedAccessor __nested_accessor; // solo exposición

   public:
    using element_type =
      add_const_t<decltype(/*conj-if-needed*/(declval<NestedAccessor::element_type>()))>;
    using reference = remove_const_t<element_type>;
    using data_handle_type = typename NestedAccessor::data_handle_type;
    using offset_policy = conjugated_accessor<NestedAccessor::offset_policy>;

    constexpr conjugated_accessor() = default;
    template<class OtherNestedAccessor>
      explicit(!is_convertible_v<OtherNestedAccessor, NestedAccessor>)
      constexpr conjugated_accessor(const conjugated_accessor<OtherNestedAccessor>& other);

    constexpr reference access(data_handle_type p, size_t i) const;

    constexpr typename offset_policy::data_handle_type
      offset(data_handle_type p, size_t i) const;

    constexpr const NestedAccessor& nested_accessor() const noexcept
      { return __nested_accessor; }
  };
}

namespace std::linalg {
  template<class InputExtents>
  using __transpose_extents_t = /* véase descripción */; // solo exposición

  template<class Layout>
  class layout_transpose {
   public:
    using nested_layout_type = Layout;

    template<class Extents>
    struct mapping {
     private:
      using __nested_mapping_type =
        typename Layout::template mapping<
          __transpose_extents_t<Extents>>;    // solo exposición

      __nested_mapping_type __nested_mapping; // solo exposición
        extents_type __extents;               // solo exposición

     public:
      using extents_type = Extents;
      using index_type = typename extents_type::index_type;
      using size_type = typename extents_type::size_type;
      using rank_type = typename extents_type::rank_type;
      using layout_type = layout_transpose;

      constexpr explicit mapping(const __nested_mapping_type& map);

      constexpr const extents_type& extents() const noexcept { return __extents; }

      constexpr index_type required_span_size() const
        { return __nested_mapping.required_span_size(); }

      template<class Index0, class Index1>
        constexpr index_type operator()(Index0 ind0, Index1 ind1) const
        { return __nested_mapping(ind1, ind0); }

      constexpr const __nested_mapping_type& nested_mapping() const noexcept
        { return __nested_mapping; }

      static constexpr bool is_always_unique() noexcept
        { return __nested_mapping_type::is_always_unique(); }
      static constexpr bool is_always_exhaustive() noexcept
        { return __nested_mapping_type::is_always_exhaustive(); }
      static constexpr bool is_always_strided() noexcept
        { return __nested_mapping_type::is_always_strided(); }
      
      constexpr bool is_unique() const 
        { return __nested_mapping.is_unique(); }
      constexpr bool is_exhaustive() const 
        { return __nested_mapping.is_exhaustive(); }
      constexpr bool is_strided() const 
        { return __nested_mapping.is_strided(); }

      constexpr index_type stride(size_t r) const;

      template<class OtherExtents>
      friend constexpr bool
        operator==(const mapping& x, const mapping<OtherExtents>& y);
    };
  };
}

namespace std::linalg {
  template<class T>
  struct __is_mdspan : false_type {}; // solo exposición

  template<class ElementType, class Extents, class Layout, class Accessor>
  struct __is_mdspan<mdspan<ElementType, Extents, Layout, Accessor>>
  : true_type {}; // solo exposición

  template<class T>
  concept __in_vector = // solo exposición
    __is_mdspan<T>::value &&
    T::rank() == 1;

  template<class T>
  concept __out_vector = // solo exposición
    __is_mdspan<T>::value &&
    T::rank() == 1 &&
    is_assignable_v<typename T::reference, typename T::element_type> &&
    T::is_always_unique();

  template<class T>
  concept __inout_vector = // solo exposición
    __is_mdspan<T>::value &&
    T::rank() == 1 &&
    is_assignable_v<typename T::reference, typename T::element_type> &&
    T::is_always_unique();

  template<class T>
  concept __in_matrix = // solo exposición
    __is_mdspan<T>::value &&
    T::rank() == 2;

  template<class T>
  concept __out_matrix = // solo exposición
    __is_mdspan<T>::value &&
    T::rank() == 2 &&
    is_assignable_v<typename T::reference, typename T::element_type> &&
   T::is_always_unique();

  template<class T>
  concept __inout_matrix = // solo exposición
    __is_mdspan<T>::value &&
    T::rank() == 2 &&
    is_assignable_v<typename T::reference, typename T::element_type> &&
    T::is_always_unique();

  template<class T>
  concept __possibly_packed_inout_matrix = // solo exposición
    __is_mdspan<T>::value &&
    T::rank() == 2 &&
    is_assignable_v<typename T::reference, typename T::element_type> &&
    (T::is_always_unique() || is_same_v<typename T::layout_type, layout_blas_packed>);

  template<class T>
  concept __in_object = // solo exposición
    __is_mdspan<T>::value &&
    (T::rank() == 1 || T::rank() == 2);

  template<class T>
  concept __out_object = // solo exposición
    __is_mdspan<T>::value &&
    (T::rank() == 1 || T::rank() == 2) &&
    is_assignable_v<typename T::reference, typename T::element_type> &&
    T::is_always_unique();

  template<class T>
  concept __inout_object = // solo exposición
    __is_mdspan<T>::value &&
    (T::rank() == 1 || T::rank() == 2) &&
    is_assignable_v<typename T::reference, typename T::element_type> &&
    T::is_always_unique();
}