Package 'bit64' provides serializable S3 atomic 64bit (signed)
integers. These are useful for handling database keys and exact
counting in +-2^63. WARNING: do not use them as replacement for 32bit
integers, integer64 are not supported for subscripting by R-core and
they have different semantics when combined with double,
e.g. integer64 + double => integer64. Class integer64 can be used in
vectors, matrices, arrays and data.frames. Methods are available for
coercion from and to logicals, integers, doubles, characters and
factors as well as many elementwise and summary functions. Many fast
algorithmic operations such as 'match' and 'order' support interactive
data exploration and manipulation and optionally leverage caching.