Advice on linked list

Hello all, I am creating a program which has a linked list. The linked list contains 2 different structs: variable, and function. For a while I was connecting the lists by using void pointers and using casts to get their data, e.g.: void *previous, *next;
((struct variable *)temp->previous).
Basically, I am placing functions in the same list as variables and vice-versa. I was wondering, would it be better to just place them in separate lists? Is it not worth the trouble to do it my way?

did you say a list? I heard there's this language, called LISP, I think it's real good at lists.