xgenerator
Defined in xtensor/xgenerator.hpp
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template<class F, class R, class S>
class xgenerator : public xt::xsharable_expression<xgenerator<F, R, S>>, public xt::xconst_iterable<xgenerator<F, R, S>>, public xt::xconst_accessible<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
Size and shape
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inline const inner_shape_type &shape() const noexcept
Returns the shape of the xgenerator.
Broadcasting
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template<class O>
inline bool broadcast_shape(O &shape, bool reuse_cache = false) const Broadcast the shape of the function to the specified parameter.
- Parameters:
shape – the result shape
reuse_cache – parameter for internal optimization
- Returns:
a boolean indicating whether the broadcasting is trivial
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template<class O>
inline bool has_linear_assign(const O&) const noexcept Checks whether the xgenerator can be linearly assigned to an expression with the specified strides.
- Returns:
a boolean indicating whether a linear assign is possible
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template<class O>
inline auto reshape(O &&shape) const & Reshapes the generator and keeps old elements.
The
shape
argument can have one of its value equal to-1
, in this case the value is inferred from the number of elements in the generator and the remaining values in theshape
.auto a = xt::arange<double>(50).reshape({-1, 10}); //a.shape() is {5, 10}
- Parameters:
shape – the new shape (has to have same number of elements as the original generator)
Data
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template<class ...Args>
inline auto operator()(Args... args) const -> const_reference 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.
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template<class ...Args>
inline auto unchecked(Args... args) const -> const_reference 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 preferred 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.
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template<class It>
inline auto element(It first, It last) const -> const_reference 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.
Public Functions
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inline size_type shape(size_type index) const
Returns the i-th dimension of the expression.