clear-input

clear-input Function

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

Expanded Reference: clear-input

tip

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(clear-input )