66 lines
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66 lines
5.3 KiB
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<TITLE>CLHS: Macro PRINT-UNREADABLE-OBJECT</TITLE>
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<A NAME="print-unreadable-object"><I>Macro</I> <B>PRINT-UNREADABLE-OBJECT</B></A> <P>
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<P><B>Syntax:</B><P>
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<P>
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<B>print-unreadable-object</B> <I>(object stream <TT>&key</TT> type identity) <I>form</I><B>*</B></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>object</I>---an <A REL=DEFINITION HREF="26_glo_o.htm#object"><I>object</I></A>; evaluated. <P>
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<I>stream</I>---a <A REL=DEFINITION HREF="26_glo_s.htm#stream_designator"><I>stream designator</I></A>; evaluated. <P>
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<I>type</I>---a <A REL=DEFINITION HREF="26_glo_g.htm#generalized_boolean"><I>generalized boolean</I></A>; evaluated. <P>
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<I>identity</I>---a <A REL=DEFINITION HREF="26_glo_g.htm#generalized_boolean"><I>generalized boolean</I></A>; evaluated. <P>
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<I>forms</I>---an <A REL=DEFINITION HREF="26_glo_i.htm#implicit_progn"><I>implicit progn</I></A>. <P>
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<P><B>Description:</B><P>
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<P>
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Outputs a printed representation of <I>object</I> on <I>stream</I>, beginning with ``<TT>#<</TT>'' and ending with ``<TT>></TT>''. Everything output to <I>stream</I> by the body <I>forms</I> is enclosed in the the angle brackets. If <I>type</I> is <A REL=DEFINITION HREF="26_glo_t.htm#true"><I>true</I></A>, the output from <I>forms</I> is preceded by a brief description of the <I>object</I>'s <A REL=DEFINITION HREF="26_glo_t.htm#type"><I>type</I></A> and a space character. If <I>identity</I> is <A REL=DEFINITION HREF="26_glo_t.htm#true"><I>true</I></A>, the output from <I>forms</I> is followed by a space character and a representation of the <I>object</I>'s identity, typically a storage address. <P>
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If either <I>type</I> or <I>identity</I> is not supplied, its value is <A REL=DEFINITION HREF="26_glo_f.htm#false"><I>false</I></A>. It is valid to omit the body <I>forms</I>. If <I>type</I> and <I>identity</I> are both true and there are no body <I>forms</I>, only one space character separates the type and the identity. <P>
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<P><B>Examples:</B><P>
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<P>
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;; Note that in this example, the precise form of the output ;; is <A REL=DEFINITION HREF="26_glo_i.htm#implementation-dependent"><I>implementation-dependent</I></A>. <P>
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<PRE>
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(defmethod print-object ((obj airplane) stream)
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(print-unreadable-object (obj stream :type t :identity t)
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(princ (tail-number obj) stream)))
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(prin1-to-string my-airplane)
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=> "#<Airplane NW0773 36000123135>"
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OR=> "#<FAA:AIRPLANE NW0773 17>"
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</PRE>
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</TT> <P>
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<P><B>Affected By:</B> None.
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<P>
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<P><B>Exceptional Situations:</B><P>
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<P>
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If <A REL=DEFINITION HREF="v_pr_rda.htm#STprint-readablyST"><B>*print-readably*</B></A> is <A REL=DEFINITION HREF="26_glo_t.htm#true"><I>true</I></A>, <A REL=DEFINITION HREF="#print-unreadable-object"><B>print-unreadable-object</B></A> signals an error of <A REL=DEFINITION HREF="26_glo_t.htm#type"><I>type</I></A> <A REL=DEFINITION HREF="e_pr_not.htm#print-not-readable"><B>print-not-readable</B></A> without printing anything. <P>
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<P><B>See Also:</B> None.
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<P>
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<P><B>Notes:</B> None.
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<P>
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<P>
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<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/iss089.htm">DATA-IO:ADD-SUPPORT</A><P></UL><HR>
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