Caml_int64let mk: lo:int => hi:int => t;let min_int: t;let max_int: t;let one: t;let zero: t;let neg_one: t;let of_int32: int => t;let to_int32: t => int;let is_zero: t => bool;let equal_undefined: t => Js.undefined(t) => bool;let equal_nullable: t => Js.nullable(t) => bool;let to_float: t => float;let of_float: float => t;let float_of_bits: t => float;let bits_of_float: float => t;bits_of_float fl it is undefined behaivor when f is NaN
let unsafe_to_int64: t => int64;let unsafe_of_int64: int64 => t;