Yes, there is a limit to expressions in lite-C. This is normally only relevant for the pattern finder that can create huge expressions, therefore the FAST flag can be used for a workaround. There is no such workaround for DTREE. But for some sort of consolation: if a decision tree is so complex that the compiler can not compile it, the system would be curve fitted and useless anyway. A sign of a predictive edge is a relatively simple and short decision tree.