template <class stateT> class fpos;
Stream position class template
Class template used as a template for types to indicate positions in streams. The template depends on the state type stateT.
The details of this class are implementation-defined, but has at least two members:
stateT state() const;
Each either getting or setting the value of the state type (stateT) kept internally by the object.
Objects of any fpos instanced type support construction and conversion from
int, and allow consistent conversions to/from values of type streamoff (as well as being added or subtracted values of this type).
Two objects of this type can be compared with operators == and !=. They can also be subtracted, which yields a value of type streamoff.
The synonym types streampos and wstreampos are instantiations of this template with mbstate_t as stateT.