function
(cmp x y )
Returns -1 if x is strictly less than y , 1 if y is strictly greater
than x , and 0 otherwise. To return 0 , x and y must be the exact
same type.
(cmp 0.0 0 )
# => 0
(cmp [1 2 ] [1 2 3 ])
# => -1
(cmp 1.0 2 )
# => -1