39 lines
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39 lines
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<TITLE>CLHS: Section 1.4.4.20.1</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="01_ddt.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Previous]" SRC="../Graphics/Prev.gif" ALIGN=Bottom></A><A REL=UP HREF="01_ddt.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Up]" SRC="../Graphics/Up.gif" ALIGN=Bottom></A><A REL=NEXT HREF="01_ddtb.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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1.4.4.20.1 Special ``Syntax'' Notations for Overloaded Operators</H2> <P>
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If two descriptions exist for the same operation but with different numbers of arguments, then the extra arguments are to be treated as optional. For example, this pair of lines: <P>
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<B>file-position</B> <I>stream</I> => <I>position</I><P>
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<B>file-position</B> <I>stream position-spec</I> => <I>success-p</I><P>
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<P>
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is operationally equivalent to this line: <P>
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<B>file-position</B> <I>stream <TT>&optional</TT> position-spec</I> => <I>result</I><P>
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<P>
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and differs only in that it provides on opportunity to introduce different names for <A REL=DEFINITION HREF="26_glo_p.htm#parameter"><I>parameter</I></A> and <A REL=DEFINITION HREF="26_glo_v.htm#value"><I>values</I></A> for each case. The separated (multi-line) notation is used when an <A REL=DEFINITION HREF="26_glo_o.htm#operator"><I>operator</I></A> is overloaded in such a way that the <A REL=DEFINITION HREF="26_glo_p.htm#parameter"><I>parameters</I></A> are used in different ways depending on how many <A REL=DEFINITION HREF="26_glo_a.htm#argument"><I>arguments</I></A> are supplied (e.g., for the <A REL=DEFINITION HREF="26_glo_f.htm#function"><I>function</I></A> <A REL=DEFINITION HREF="f_sl.htm#SL"><B>/</B></A>) or the return values are different in the two cases (e.g., for the <A REL=DEFINITION HREF="26_glo_f.htm#function"><I>function</I></A> <A REL=DEFINITION HREF="f_file_p.htm#file-position"><B>file-position</B></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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