compilation in tox virtualenv works

bfps/__init__.py

bfps/code.py

bfps/cpp/Morton_shuffler.cpp

bfps/cpp/Morton_shuffler.hpp

bfps/cpp/base.hpp

bfps/cpp/fftw_tools.cpp

bfps/cpp/fftw_tools.hpp

bfps/cpp/field_descriptor.cpp

bfps/cpp/field_descriptor.hpp

bfps/cpp/fluid_solver.cpp

bfps/cpp/fluid_solver.hpp

bfps/cpp/fluid_solver_base.cpp

bfps/cpp/fluid_solver_base.hpp

bfps/cpp/main_fluid_solver.cpp

bfps/cpp/main_p3DFFT_to_Morton.cpp

bfps/cpp/p3DFFT_to_iR.cpp

bfps/cpp/p3DFFT_to_iR.hpp

bfps/cpp/slab_field_particles.cpp

bfps/cpp/slab_field_particles.hpp

bfps/cpp/spline_n1.cpp