(* 
 * See the relevant discussion in sum-lists.fmsl.  And see also the further
 * treatment of these ideas in ./list-funcs.fmsl.
 *)
function car(l:integer*) =
    if #l = 0 then nil
    else l[1];

function cdr(l:integer*) =
    if (#l = 0) then nil
    else l[2..#l];

> car([]);
> cdr([]);
> car([1]);
> cdr([1]);
> car([1,2]);
> cdr([1,2]);
> car([1,2,3]);
> cdr([1,2,3]);