The Dcompute kernel language (which for the most part is plain D, the compiler is completely reused) has the usual set of restrictions that any kernel languages have: no exceptions, recursion, runtime (which is what betterC is about), function pointers. It still has all the the features that make D great, sane templates (will work across both host and device to a degree), ranges, CTFE (no need to precompile you lookup tables) and so on.