call to cuda from c++

I am compiling my host function in .cu file and it is accepting c++ class and allowing c++ classes to be used, but when I am trying to compile it gives me
FluidMatchFlowSegmentation.C:233: error: ‘interpolateMapStaniforthCoteCuda’ was not declared in this scope
I even used “using namespace std”

any idea?

Can we see a bit more source code, please? The error message suggests that it’s the C++ file not seeing the definition of the function in the .cu file, but without more to go on, there’s not a lot anyone can help you with.