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  ANSI Common Lisp   21 Streams   21.2 Dictionary of Streams

21.2.34 listen Function

listen &optional input-stream    generalized-boolean

Arguments and Values:
input-stream - an input stream designator. The default is standard input.

generalized-boolean - a generalized boolean.

Returns true if there is a character immediately available from input-stream; otherwise, returns false. On a non-interactive input-stream, listen returns true except when at end of file1. If an end of file is encountered, listen returns false. listen is intended to be used when input-stream obtains characters from an interactive device such as a keyboard.

 (progn (unread-char (read-char)) (list (listen) (read-char)))
 (T #\1)
 (progn (clear-input) (listen))
  NIL ;Unless you're a very fast typist!

Affected By:

See Also:
interactive-stream-p, read-char-no-hang

Allegro CL Implementation Details:

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