Function 3: zipper (CLISP)

Define a function that takes two lists as arguments and returns a single list of pairs (i.e. two element sublists). The first pair should both be the first elements from the respective lists. The second pair should be the second elements from the respective lists, and so on. If one input list is longer than the other, extra elements of the longer list are ignored. Your implementation must be recursive.

Input: Two Lists of elements of any type, potentially heterogenous. The two lists do not have to be the same length.

Output: A new list whose elements are each two-element sublists.

Examples:

> (zipper '(1 2 3 4) '(a b c d))

'((1 a) (2 b) (3 c) (4 d))

> (zipper '(1 2 3) '(4 9 5 7))

'((1 4) (2 9) (3 5))

> (zipper '(5) '( ))

'( )