multi-dimensional arrays with broadcasting and lazy computing

 xtensor is a C++ library meant for numerical analysis with multi-dimensional
 array expressions.
 .
 xtensor provides:
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   - an extensible expression system enabling lazy broadcasting.
   - an API following the idioms of the C++ standard library.
   - tools to manipulate array expressions and build upon xtensor.
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 Containers of xtensor are inspired by NumPy, the Python array programming
 library. In fact, xtensor can be used to process numpy data structures inplace
 using Python's buffer protocol. For more details on the numpy bindings, check
 out the xtensor-python project.
 .
 This package provides the header-only library.