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<!-- 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 SET-MACRO-CHARACTER, GET-MACRO-CHARACTER</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_set__1.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Previous]" SRC="../Graphics/Prev.gif" ALIGN=Bottom></A><A REL=UP HREF="c_reader.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Up]" SRC="../Graphics/Up.gif" ALIGN=Bottom></A><A REL=NEXT HREF="f_set_sy.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Next]" SRC="../Graphics/Next.gif" ALIGN=Bottom></A></H1>
<HR>
<A NAME="set-macro-character"><A NAME="get-macro-character"><I>Function</I> <B>SET-MACRO-CHARACTER, GET-MACRO-CHARACTER</B></A></A> <P>
<P><B>Syntax:</B><P>
<P>
<B>get-macro-character</B> <I>char <TT>&amp;optional</TT> readtable</I> =&gt; <I>function, non-terminating-p</I><P>
<P>
<B>set-macro-character</B> <I>char new-function <TT>&amp;optional</TT> non-terminating-p readtable</I> =&gt; <I><A REL=DEFINITION HREF="a_t.htm#t"><B>t</B></A></I><P>
<P>
<P><B>Arguments and Values:</B><P>
<P>
<I>char</I>---a <A REL=DEFINITION HREF="26_glo_c.htm#character"><I>character</I></A>. <P>
<I>non-terminating-p</I>---a <A REL=DEFINITION HREF="26_glo_g.htm#generalized_boolean"><I>generalized boolean</I></A>. The default is <A REL=DEFINITION HREF="26_glo_f.htm#false"><I>false</I></A>. <P>
<I>readtable</I>---a <A REL=DEFINITION HREF="26_glo_r.htm#readtable_designator"><I>readtable designator</I></A>. The default is the <A REL=DEFINITION HREF="26_glo_c.htm#current_readtable"><I>current readtable</I></A>. <P>
<I>function</I>---<A REL=DEFINITION HREF="a_nil.htm#nil"><B>nil</B></A>, or a <A REL=DEFINITION HREF="26_glo_d.htm#designator"><I>designator</I></A> for a <A REL=DEFINITION HREF="26_glo_f.htm#function"><I>function</I></A> of two <A REL=DEFINITION HREF="26_glo_a.htm#argument"><I>arguments</I></A>. <P>
<I>new-function</I>---a <A REL=DEFINITION HREF="26_glo_f.htm#function_designator"><I>function designator</I></A>. <P>
<P><B>Description:</B><P>
<P>
<A REL=DEFINITION HREF="#get-macro-character"><B>get-macro-character</B></A> returns as its <A REL=DEFINITION HREF="26_glo_p.htm#primary_value"><I>primary value</I></A>, <I>function</I>, the <A REL=DEFINITION HREF="26_glo_r.htm#reader_macro_function"><I>reader macro function</I></A> associated with <I>char</I> in <I>readtable</I> (if any), or else <A REL=DEFINITION HREF="a_nil.htm#nil"><B>nil</B></A> if <I>char</I> is not a <A REL=DEFINITION HREF="26_glo_m.htm#macro_character"><I>macro character</I></A> in <I>readtable</I>. The <A REL=DEFINITION HREF="26_glo_s.htm#secondary_value"><I>secondary value</I></A>, <I>non-terminating-p</I>, is <A REL=DEFINITION HREF="26_glo_t.htm#true"><I>true</I></A> if <I>char</I> is a <A REL=DEFINITION HREF="26_glo_n.htm#non-terminating"><I>non-terminating</I></A> <A REL=DEFINITION HREF="26_glo_m.htm#macro_character"><I>macro character</I></A>; otherwise, it is <A REL=DEFINITION HREF="26_glo_f.htm#false"><I>false</I></A>. <P>
<A REL=DEFINITION HREF="#set-macro-character"><B>set-macro-character</B></A> causes <I>char</I> to be a <A REL=DEFINITION HREF="26_glo_m.htm#macro_character"><I>macro character</I></A> associated with the <A REL=DEFINITION HREF="26_glo_r.htm#reader_macro_function"><I>reader macro function</I></A> <I>new-function</I> (or the <A REL=DEFINITION HREF="26_glo_d.htm#designator"><I>designator</I></A> for <I>new-function</I>) in <I>readtable</I>. If <I>non-terminating-p</I> is <A REL=DEFINITION HREF="26_glo_t.htm#true"><I>true</I></A>, <I>char</I> becomes a <A REL=DEFINITION HREF="26_glo_n.htm#non-terminating"><I>non-terminating</I></A> <A REL=DEFINITION HREF="26_glo_m.htm#macro_character"><I>macro character</I></A>; otherwise it becomes a <A REL=DEFINITION HREF="26_glo_t.htm#terminating"><I>terminating</I></A> <A REL=DEFINITION HREF="26_glo_m.htm#macro_character"><I>macro character</I></A>. <P>
<P><B>Examples:</B><P>
<P>
<PRE>
(get-macro-character #\{) =&gt; NIL, <A REL=DEFINITION HREF="26_glo_f.htm#false">false</A>
(not (get-macro-character #\;)) =&gt; <A REL=DEFINITION HREF="26_glo_f.htm#false">false</A>
</PRE>
</TT> <P>
The following is a possible definition for the <A REL=DEFINITION HREF="26_glo_s.htm#single-quote"><I>single-quote</I></A> <A REL=DEFINITION HREF="26_glo_r.htm#reader_macro"><I>reader macro</I></A> in <A REL=DEFINITION HREF="26_glo_s.htm#standard_syntax"><I>standard syntax</I></A>: <P>
<PRE>
(defun single-quote-reader (stream char)
(declare (ignore char))
(list 'quote (read stream t nil t))) =&gt; SINGLE-QUOTE-READER
(set-macro-character #\' #'single-quote-reader) =&gt; T
</PRE>
</TT> <P>
Here <TT>single-quote-reader</TT> reads an <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>object</I></A> following the <A REL=DEFINITION HREF="26_glo_s.htm#single-quote"><I>single-quote</I></A> and returns a <A REL=DEFINITION HREF="26_glo_l.htm#list"><I>list</I></A> of <A REL=DEFINITION HREF="s_quote.htm#quote"><B>quote</B></A> and that <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>object</I></A>. The <I>char</I> argument is ignored. <P>
The following is a possible definition for the <A REL=DEFINITION HREF="26_glo_s.htm#semicolon"><I>semicolon</I></A> <A REL=DEFINITION HREF="26_glo_r.htm#reader_macro"><I>reader macro</I></A> in <A REL=DEFINITION HREF="26_glo_s.htm#standard_syntax"><I>standard syntax</I></A>: <P>
<PRE>
(defun semicolon-reader (stream char)
(declare (ignore char))
;; First swallow the rest of the current input line.
;; End-of-file is acceptable for terminating the comment.
(do () ((char= (read-char stream nil #\Newline t) #\Newline)))
;; Return zero values.
(values)) =&gt; SEMICOLON-READER
(set-macro-character #\; #'semicolon-reader) =&gt; T
</PRE>
</TT> <P>
<P><B>Side Effects:</B><P>
<P>
The <I>readtable</I> is modified. <P>
<P><B>Affected By:</B> None.
<P>
<P><B>Exceptional Situations:</B> None.
<P>
<P><B>See Also:</B><P>
<P>
<A REL=DEFINITION HREF="v_rdtabl.htm#STreadtableST"><B>*readtable*</B></A> <P>
<P><B>Notes:</B> None.
<P>
<P><HR>The following <A REL=META HREF="../Front/X3J13Iss.htm">X3J13 cleanup issue</A>, <I>not part of the specification</I>, applies to this section:<P><UL><LI> <A REL=CHILD HREF="../Issues/iss184.htm">GET-MACRO-CHARACTER-READTABLE:NIL-STANDARD</A><P></UL><HR>
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