(neg-int? x)
Return true if x is a negative fixed precision integer
(neg-int? -1)
;;=> true
(neg-int? -9223372036854775808)
;;=> true
;;;; false for non-negative values
(neg-int? 0)
;;=> false
(neg-int? 1)
;;=> false
;;;; false for decimal values
(neg-int? -1.0)
;;=> false
(neg-int? -1/2)
;;=> false
;;;; false for BigInt values
(neg-int? -1N)
;;=> false
(neg-int? -9223372036854775809)
;;=> false