Define a sheme function ca (for count-atoms) that will count the number of atoms in a list, at all levels

How do you best explain a data structure that uses a double-linked list?

struct insert_at_back_of_sll { // Function takes a constant Book as a parameter, inserts that book at the // back of a singly linked list, and returns nothing. void operator()(const Book& book) { /// TO-DO (3) /// // Write the lines of code to insert "book" at the back of "my_sll". Since // the SLL has no size() function and no tail pointer, you must walk the // list looking for the last node. // // HINT: Do not attempt to insert after "my_sll.end()". // ///// END-T0-DO (3) ||||// } std::forward_list& my_sll; };

Lists and tuples are two distinct data structures.