open_null_stream/1open_null_stream(-Stream)
opens an output stream that is not connected to any file and unifies its stream object with Stream.
Characters or terms that are sent
to this stream are thrown away. This predicate is useful because
various pieces of local state are kept for null streams: the
predicates character_count/2, line_count/2, and
line_position/2 can be used on these streams (see
ref-iou-sos).
If Stream is fully instantiated at the time of the call to
open_null_stream/1, the call simply fails.
character_count/2, line_count/2,
line_position/2