free_term (Conditional t1 f t2 r) = Conditional t1' f' t2' r
     where t1' = free_term t1
           t2' = free_term t2
           f' = free_formula f
free_term (Conditional t1 f t2 r) = Conditional t1' f' t2' r
     where t1' = free_term t1
           t2' = free_term t2
           f' = free_formula f
free_term (Conditional t1 f t2 r) = Conditional t1' f' t2' r
     where t1' = free_term t1
           t2' = free_term t2
           f' = free_formula f