When following the install instructions: https://github.com/xtensor-stack/xtensor-fftw#installation
The required headers do not get installed, e.g. basic_float.hpp, which is included from basic.hpp does not get installed.
This is, I believe, because ${XTENSOR_FFTW_HEADERS} is defined here without those headers:
https://github.com/xtensor-stack/xtensor-fftw/blob/master/CMakeLists.txt#L179