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1. JohanMabille commented on Sep 6, 2020

   

   JohanMabille

   on Sep 6, 2020

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   You can rely on SFINAE but you'll have to specialize the "testing" function for different types. For instance:

   template <class E, size_t N>
   struct has_rank : std::false_type
   {
   };
   
   template <class T>
   struct has_rank<xt::xtensor<T, 2>, 2>
       : std::true_type
   {
   };
   
   template <class T, size_t N1, size_t N2>
   struct has_rank<xt::xtensor_fixed<T, xt::xshape<N1, N2>>>
       : std::true_type
   {
   };
   
   template <class E>
   std::enable_if_t<has_rank<E, 2>> foo(E& e)
   {
       // ...
   }

   This is going to be really cumbersome. Another solution would be to add a rank property to the different classes of xtensor, so the testing function can work for any kind of expression:

   template <class E, size_t N>
   struct has_rank
   {
       using type = std::integral_constant<bool, E::rank == N>;
   };
   
   template <class E, size_t N>
   using has_rank_t = typename has_rank<E, N>::type;
2. tdegeus commented on Sep 7, 2020

   

   tdegeus

   on Sep 7, 2020

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   Thanks @JohanMabille ! The latter would be a really nice solution for me, and I guess something that could be beneficial for others. Could be a great extension for the next release. I will submit a PR today or tomorrow that we can iterate on.

   Reacted by Johan Mabille
3. tdegeus

   self-assigned this

   on Sep 7, 2020
4. tdegeus commented on Sep 7, 2020

   

   tdegeus

   on Sep 7, 2020

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   @JohanMabille What would you say that E::rank should be for xarray? Or should there be a second variable: has_fixed_rank?
5. JohanMabille commented on Sep 7, 2020

   

   JohanMabille

   on Sep 7, 2020

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   I think we could use SIZE_MAX for a dynamic rank.
6. tdegeus

   closed this as completedin #2138on Sep 8, 2020