66 lines
3.8 KiB
HTML
66 lines
3.8 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3O//DTD W3 HTML 2.0//EN">
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<!Converted with LaTeX2HTML 0.6.5 (Tue Nov 15 1994) by Nikos Drakos (nikos@cbl.leeds.ac.uk), CBLU, University of Leeds >
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<HEAD>
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<TITLE>27.1. Introduction</TITLE>
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</HEAD>
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<BODY>
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<meta name="description" value=" Introduction">
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<meta name="keywords" value="clm">
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<meta name="resource-type" value="document">
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<meta name="distribution" value="global">
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<P>
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<b>Common Lisp the Language, 2nd Edition</b>
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<BR> <HR><A NAME=tex2html4740 HREF="node255.html"><IMG ALIGN=BOTTOM ALT="next" SRC="icons/next_motif.gif"></A> <A NAME=tex2html4738 HREF="node253.html"><IMG ALIGN=BOTTOM ALT="up" SRC="icons/up_motif.gif"></A> <A NAME=tex2html4732 HREF="node253.html"><IMG ALIGN=BOTTOM ALT="previous" SRC="icons/previous_motif.gif"></A> <A NAME=tex2html4742 HREF="node1.html"><IMG ALIGN=BOTTOM ALT="contents" SRC="icons/contents_motif.gif"></A> <A NAME=tex2html4743 HREF="index.html"><IMG ALIGN=BOTTOM ALT="index" SRC="icons/index_motif.gif"></A> <BR>
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<B> Next:</B> <A NAME=tex2html4741 HREF="node255.html"> Pretty Printing Control </A>
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<B>Up:</B> <A NAME=tex2html4739 HREF="node253.html"> Pretty Printing</A>
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<B> Previous:</B> <A NAME=tex2html4733 HREF="node253.html"> Pretty Printing</A>
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<HR> <P>
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<H1><A NAME=SECTION003110000000000000000>27.1. Introduction</A></H1>
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<P>
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<img align=bottom alt="change_begin" src="gif/change_begin.gif"><br>
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Pretty printing has traditionally been a black box process, displaying
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program code using a set of fixed layout rules. Its utility can be greatly
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enhanced by opening it up to user control. The facilities described
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in this chapter provide general and powerful means for specifying pretty-printing
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behavior.
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<P>
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By providing direct access to the mechanisms within the pretty printer that
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make dynamic decisions about layout, the macros and functions
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<tt>pprint-logical-block</tt>, <tt>pprint-newline</tt>, and <tt>pprint-indent</tt> make
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it possible to specify pretty printing layout rules as a part of any
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function that produces output. They also make it very easy for the
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function to support
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detection of circularity and sharing and abbreviation based on length and
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nesting depth. Using the function
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<tt>set-pprint-dispatch</tt>, one can associate a user-defined pretty
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printing function with any type of object. A small set of new <tt>format</tt>
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directives allows concise implementation of user-defined pretty-printing
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functions.
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Together, these facilities
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enable users to redefine the way code is displayed and allow the full power
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of pretty printing to be applied to complex combinations of data
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structures.
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<P>
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<hr>
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<b>Implementation note:</b> This chapter describes the interface of
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the XP pretty printer. XP is described fully
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in [<A HREF="node368.html#XPPRETTYPRINTER">54</A>],
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which also explains how to obtain a portable implementation. XP uses
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a highly efficient linear-time algorithm. When properly integrated into a
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Common Lisp, this algorithm supports pretty printing that is only
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fractionally slower than ordinary printing.
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<hr>
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<br><img align=bottom alt="change_end" src="gif/change_end.gif">
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<P>
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<BR> <HR><A NAME=tex2html4740 HREF="node255.html"><IMG ALIGN=BOTTOM ALT="next" SRC="icons/next_motif.gif"></A> <A NAME=tex2html4738 HREF="node253.html"><IMG ALIGN=BOTTOM ALT="up" SRC="icons/up_motif.gif"></A> <A NAME=tex2html4732 HREF="node253.html"><IMG ALIGN=BOTTOM ALT="previous" SRC="icons/previous_motif.gif"></A> <A NAME=tex2html4742 HREF="node1.html"><IMG ALIGN=BOTTOM ALT="contents" SRC="icons/contents_motif.gif"></A> <A NAME=tex2html4743 HREF="index.html"><IMG ALIGN=BOTTOM ALT="index" SRC="icons/index_motif.gif"></A> <BR>
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<B> Next:</B> <A NAME=tex2html4741 HREF="node255.html"> Pretty Printing Control </A>
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<B>Up:</B> <A NAME=tex2html4739 HREF="node253.html"> Pretty Printing</A>
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<B> Previous:</B> <A NAME=tex2html4733 HREF="node253.html"> Pretty Printing</A>
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<HR> <P>
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<HR>
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<P><ADDRESS>
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AI.Repository@cs.cmu.edu
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</ADDRESS>
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</BODY>
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