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Function CLEAR-INPUT

Syntax:

clear-input &optional input-stream => nil

Arguments and Values:

input-stream---an input stream designator. The default is standard input.

Description:

Clears any available input from input-stream.

If clear-input does not make sense for input-stream, then clear-input does nothing.

Examples:

;; The exact I/O behavior of this example might vary from implementation
;; to implementation depending on the kind of interactive buffering that
;; occurs. (The call to SLEEP here is intended to help even out the 
;; differences in implementations which do not do line-at-a-time buffering.)
(defun read-sleepily (&optional (clear-p nil) (zzz 0))
 (list (progn (print '>) (read))
 ;; Note that input typed within the first ZZZ seconds 
 ;; will be discarded.
 (progn (print '>) 
 (if zzz (sleep zzz))
 (print '>>)
 (if clear-p (clear-input))
 (read))))
(read-sleepily)
>> > 10
>> >
>> >> 20
=> (10 20)
(read-sleepily t)
>> > 10
>> >
>> >> 20
=> (10 20)
(read-sleepily t 10)
>> > 10
>> > 20 ; Some implementations won't echo typeahead here.
>> >> 30
=> (10 30)

Side Effects:

The input-stream is modified.

Affected By:

*standard-input*

Exceptional Situations:

Should signal an error of type type-error if input-stream is not a stream designator.

See Also:

clear-output

Notes: None.