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at(+Stream, -Pointer)

Succeeds if Position is the position of the stream Stream.
Stream
Integer (stream number) or Atom (reserved or user-defined symbolic stream name).
Pointer
Integer or variable.

Description

Unifies Position with the position of the given Stream, which is defined as follows: Stream can be a symbolic stream name or a physical stream number.

Modes and Determinism

Exceptions

(4) instantiation fault
Stream is not instantiated.
(5) type error
Pointer is instantiated to a non-integer.
(5) type error
Stream is instantiated to neither an integer nor an atom.
(192) illegal stream mode
Stream is an illegal stream mode.

Examples

Success:
      [eclipse]: open(file1,write,s), at(s, P1),
      > write(s, 1234567890), at(s, P2), close(s).
      P1 = 0
      P2 = 10
      yes.
      [eclipse]: open(file1,update,s), at(s, P1), read(s, T),
      > at(s, P2), close(s).
      P1 = 0
      T = 1234567890
      P2 = 10
      yes.

Error:
      at(Stream, 4).      (Error 4).
      at("3", Position).   (Error 5).
      at(7, 4.3).         (Error 5).



See Also

at_eof / 1, seek / 2