current_stream(File, Mode, Stream) succeeds if
Stream is a stream that is currently open on file File in mode
Mode, where Mode is either read, write, or
append. None of the arguments need be initially instantiated.
This predicate is nondeterminate and can be used to backtrack through all
open streams.
current_stream/3 ignores certain predefined streams, including
the initial values of the special streams for the standard input,
output, and error channels.
See mpg-ref-current_stream.
stream_property(Stream, Property) succeeds if
Stream is a currently open stream with property Property.
Predefined streams, like the three standard channels, are not ignored.
See mpg-ref-stream_property.