A Segment object cannot work without a host. If the object is default constructed, the host must be set by setHost before the segment can be used.

If a segment object is constructed by the copy constructor, the members of the new constructed object are set to the same values as the members in the source object; the host object is not modified. Note that this is a special case, since all other copy operations result in changes of the host object.

begin must be a valid position/iterator in host. If begin is omitted, the suffix segment corresponding to the whole sequence host is constructed. This is the same segment that is returned by goBegin.