90 lines
4.5 KiB
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90 lines
4.5 KiB
HTML
<!-- Common Lisp HyperSpec (TM), version 7.0 generated by Kent M. Pitman on Mon, 11-Apr-2005 2:31am EDT -->
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<TITLE>CLHS: Function CLEAR-INPUT</TITLE>
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<H1><A REV=MADE HREF="http://www.lispworks.com/"><IMG WIDTH=80 HEIGHT=65 ALT="[LISPWORKS]" SRC="../Graphics/LWSmall.gif" ALIGN=Bottom></A><A REL=TOP HREF="../Front/index.htm"><IMG WIDTH=237 HEIGHT=65 ALT="[Common Lisp HyperSpec (TM)]" SRC="../Graphics/CLHS_Sm.gif" ALIGN=Bottom></A> <A REL=PREV HREF="f_listen.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Previous]" SRC="../Graphics/Prev.gif" ALIGN=Bottom></A><A REL=UP HREF="c_stream.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Up]" SRC="../Graphics/Up.gif" ALIGN=Bottom></A><A REL=NEXT HREF="f_finish.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Next]" SRC="../Graphics/Next.gif" ALIGN=Bottom></A></H1>
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<A NAME="clear-input"><I>Function</I> <B>CLEAR-INPUT</B></A> <P>
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<P><B>Syntax:</B><P>
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<P>
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<B>clear-input</B> <I><TT>&optional</TT> input-stream</I> => <I><A REL=DEFINITION HREF="a_nil.htm#nil"><B>nil</B></A></I><P>
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<P>
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<P><B>Arguments and Values:</B><P>
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<P>
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<I>input-stream</I>---an <A REL=DEFINITION HREF="26_glo_i.htm#input"><I>input</I></A> <A REL=DEFINITION HREF="26_glo_s.htm#stream_designator"><I>stream designator</I></A>. The default is <A REL=DEFINITION HREF="26_glo_s.htm#standard_input"><I>standard input</I></A>. <P>
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<P><B>Description:</B><P>
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<P>
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Clears any available input from <I>input-stream</I>. <P>
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If <A REL=DEFINITION HREF="#clear-input"><B>clear-input</B></A> does not make sense for <I>input-stream</I>, then <A REL=DEFINITION HREF="#clear-input"><B>clear-input</B></A> does nothing. <P>
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<P><B>Examples:</B><P>
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<PRE>
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;; The exact I/O behavior of this example might vary from implementation
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;; to implementation depending on the kind of interactive buffering that
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;; occurs. (The call to SLEEP here is intended to help even out the
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;; differences in implementations which do not do line-at-a-time buffering.)
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(defun read-sleepily (&optional (clear-p nil) (zzz 0))
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(list (progn (print '>) (read))
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;; Note that input typed within the first ZZZ seconds
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;; will be discarded.
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(progn (print '>)
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(if zzz (sleep zzz))
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(print '>>)
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(if clear-p (clear-input))
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(read))))
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(read-sleepily)
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>> > 10
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>> >
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>> >> 20
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=> (10 20)
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(read-sleepily t)
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>> > 10
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>> >
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>> >> 20
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=> (10 20)
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(read-sleepily t 10)
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>> > 10
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>> > 20 ; Some implementations won't echo typeahead here.
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>> >> 30
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=> (10 30)
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</PRE>
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</TT> <P>
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<P><B>Side Effects:</B><P>
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<P>
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The <I>input-stream</I> is modified. <P>
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<P><B>Affected By:</B><P>
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<P>
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<A REL=DEFINITION HREF="v_debug_.htm#STstandard-inputST"><B>*standard-input*</B></A> <P>
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<P><B>Exceptional Situations:</B><P>
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<P>
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Should signal an error of <A REL=DEFINITION HREF="26_glo_t.htm#type"><I>type</I></A> <A REL=DEFINITION HREF="e_tp_err.htm#type-error"><B>type-error</B></A> if <I>input-stream</I> is not a <A REL=DEFINITION HREF="26_glo_s.htm#stream_designator"><I>stream designator</I></A>. <P>
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<P><B>See Also:</B><P>
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<P>
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<A REL=DEFINITION HREF="f_finish.htm#clear-output"><B>clear-output</B></A> <P>
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<P><B>Notes:</B> None.
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<P>
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