assert arg!=null;
if(!(arg instanceof FunctionCall)) {
throw new EvalException("invalid .Internal() argument");
}
FunctionCall internalCall = (FunctionCall) arg;
Symbol internalName = (Symbol)internalCall.getFunction();
SEXP function = Primitives.getInternal(internalName);
if(function==null || function == Null.INSTANCE) {
throw new EvalException(String.format("no internal function \"%s\"", internalName.getPrintName()));
}
return ((Function)function).apply(context, rho, internalCall, internalCall.getArguments());
}