xgenerator

Defined in xtensor/xgenerator.hpp

template <class F, class R, class S>
class xgenerator : public xt::xexpression<xgenerator<F, R, S>>, public xt::xconst_iterable<xgenerator<F, R, S>>, public extension::xgenerator_base_t<F, R, S>

Multidimensional function operating on indices.

The xgenerator class implements a multidimensional function, generating a value from the supplied indices.

Template Parameters
  • F: the function type
  • R: the return type of the function
  • S: the shape type of the generator

Constructor

template <class Func>
xgenerator(Func &&f, const S &shape)

Constructs an xgenerator applying the specified function over the given shape.

Parameters
  • f: the function to apply
  • shape: the shape of the xgenerator

Size and shape

auto size() const

Returns the size of the expression.

auto dimension() const

Returns the number of dimensions of the function.

auto shape() const

Returns the shape of the xgenerator.

Data

template <class... Args>
auto operator()(Args... args) const

Returns the evaluated element at the specified position in the function.

Parameters
  • args: a list of indices specifying the position in the function. Indices must be unsigned integers, the number of indices should be equal or greater than the number of dimensions of the function.

template <class... Args>
auto at(Args... args) const

Returns a constant reference to the element at the specified position in the expression, after dimension and bounds checking.

Parameters
  • args: a list of indices specifying the position in the function. Indices must be unsigned integers, the number of indices should be equal to the number of dimensions of the expression.
Exceptions
  • std::out_of_range: if the number of argument is greater than the number of dimensions or if indices are out of bounds.

template <class... Args>
auto unchecked(Args... args) const

Returns a constant reference to the element at the specified position in the expression.

Warning
This method is meant for performance, for expressions with a dynamic number of dimensions (i.e. not known at compile time). Since it may have undefined behavior (see parameters), operator() should be prefered whenever it is possible.
Warning
This method is NOT compatible with broadcasting, meaning the following code has undefined behavior: 
xt::xarray<double> a = {{0, 1}, {2, 3}};
xt::xarray<double> b = {0, 1};
auto fd = a + b;
double res = fd.uncheked(0, 1);
Parameters
  • args: a list of indices specifying the position in the expression. Indices must be unsigned integers, the number of indices must be equal to the number of dimensions of the expression, else the behavior is undefined.

template <class It>
auto element(It first, It last) const

Returns a constant reference to the element at the specified position in the function.

Parameters
  • first: iterator starting the sequence of indices
  • last: iterator ending the sequence of indices The number of indices in the sequence should be equal to or greater than the number of dimensions of the container.

Broadcasting

template <class O>
bool broadcast_shape(O &shape, bool reuse_cache = false) const

Broadcast the shape of the function to the specified parameter.

Return
a boolean indicating whether the broadcasting is trivial
Parameters
  • shape: the result shape
  • reuse_cache: parameter for internal optimization

template <class O>
bool has_linear_assign(const O&) const

Checks whether the xgenerator can be linearly assigned to an expression with the specified strides.

Return
a boolean indicating whether a linear assign is possible