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30 lines
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<TITLE>CLHS: Section 23.1.3.1</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="23_ac.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Previous]" SRC="../Graphics/Prev.gif" ALIGN=Bottom></A><A REL=UP HREF="23_ac.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Up]" SRC="../Graphics/Up.gif" ALIGN=Bottom></A><A REL=NEXT HREF="23_acb.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Next]" SRC="../Graphics/Next.gif" ALIGN=Bottom></A></H1>
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<H2>
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23.1.3.1 The EOF-ERROR-P argument</H2> <P>
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<I>Eof-error-p</I> in input function calls controls what happens if input is from a file (or any other input source that has a definite end) and the end of the file is reached. If <I>eof-error-p</I> is <A REL=DEFINITION HREF="26_glo_t.htm#true"><I>true</I></A> (the default), an error of <A REL=DEFINITION HREF="26_glo_t.htm#type"><I>type</I></A> <A REL=DEFINITION HREF="e_end_of.htm#end-of-file"><B>end-of-file</B></A> is signaled at end of file. If it is <A REL=DEFINITION HREF="26_glo_f.htm#false"><I>false</I></A>, then no error is signaled, and instead the function returns <I>eof-value</I>. <P>
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Functions such as <A REL=DEFINITION HREF="f_rd_rd.htm#read"><B>read</B></A> that read the representation of an <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>object</I></A> rather than a single character always signals an error, regardless of <I>eof-error-p</I>, if the file ends in the middle of an object representation. For example, if a file does not contain enough right parentheses to balance the left parentheses in it, <A REL=DEFINITION HREF="f_rd_rd.htm#read"><B>read</B></A> signals an error. If a file ends in a <A REL=DEFINITION HREF="26_glo_s.htm#symbol"><I>symbol</I></A> or a <A REL=DEFINITION HREF="26_glo_n.htm#number"><I>number</I></A> immediately followed by end-of-file, <A REL=DEFINITION HREF="f_rd_rd.htm#read"><B>read</B></A> reads the <A REL=DEFINITION HREF="26_glo_s.htm#symbol"><I>symbol</I></A> or <A REL=DEFINITION HREF="26_glo_n.htm#number"><I>number</I></A> successfully and when called again will act according to <I>eof-error-p</I>. Similarly, the <A REL=DEFINITION HREF="26_glo_f.htm#function"><I>function</I></A> <A REL=DEFINITION HREF="f_rd_lin.htm#read-line"><B>read-line</B></A> successfully reads the last line of a file even if that line is terminated by end-of-file rather than the newline character. Ignorable text, such as lines containing only <A REL=DEFINITION HREF="26_glo_w.htm#whitespace"><I>whitespace</I></A>[2] or comments, are not considered to begin an <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>object</I></A>; if <A REL=DEFINITION HREF="f_rd_rd.htm#read"><B>read</B></A> begins to read an <A REL=DEFINITION HREF="26_glo_e.htm#expression"><I>expression</I></A> but sees only such ignorable text, it does not consider the file to end in the middle of an <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>object</I></A>. Thus an <I>eof-error-p</I> argument controls what happens when the file ends between <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>objects</I></A>. <P>
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<A REL=COPYRIGHT HREF="../Front/Help.htm#Legal"><I>Copyright 1996-2005, LispWorks Ltd. All rights reserved.</I></A><P>
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