CLHS: Function CLEAR-INPUT

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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.

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