set_stream(+StreamId, +Stream)

+StreamId

Atom.

+Stream

Integer (stream number) or Atom (reserved or user-defined symbolic stream name).

Description

Logical streams may be matched to their physical stream numbers by using get_stream/2.

Stream can be any existing stream number or symbolic stream name as long as it has a mode compatible with that of StreamId.

StreamId can be a user-defined symbolic stream name, or else one of the system systems: input , output , error, user, warning_output, log_output.

A user-defined symbolic stream is not automatically updated when the stream to which it points is changed or closed.

Fail Conditions

Resatisfiable

Exceptions

(4) instantiation fault

Either StreamId or Stream is uninstantiated.

(5) type error

Either StreamId is not an atom or Stream is not a stream number or symbolic stream name.

(193) illegal stream specification

Stream is an illegal stream specification.

(194) too many symbolic names of a stream

A physical stream has more than 255 logical stream names assigned to it.

Examples

Success:
      [eclipse]: open(file1,update,s), set_stream(output,s),
      > writeln(output,hi), flush(output).
      yes.
      [eclipse]: seek(s,0), read(s,X).
      X = hi
      yes.
Error:
      set_stream(a, S).        (Error 4).
      set_stream(1.0, S).      (Error 5).
      set_stream(a, nonex).    (Error 193).

See Also