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shared generator expressions #2673

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@nodatapoints

I would like to wrap generator expressions in a function like in the following example.

inline auto build(int n) {
    auto x = xt::make_xshared(xt::arange(n));
    return x*x;
}

xt::xtensor<double, 1> array;
array = build(10);

Currently this gives an error

/usr/include/xtensor/xexpression.hpp:575:9: error:
    ‘class xt::xgenerator<xt::detail::arange_generator<int, int, int>, int,
    std::array<long unsigned int, 1> >’ has no member named ‘linear_begin’
  575 |         XTENSOR_FORWARD_METHOD(linear_begin)

As far as I understand, this is currently only possible for xexpressions of evaluated expressions.
My current workarounds are:

  • Evaluating the generator. This sacrifices laziness.
  • Passing array by reference. This is not idiomatic and only works if the assignment results in a evaluation.

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