chapter18.tex

% -*- coding: utf-8 -*-
\documentclass{book}

\input{preamble}
\setcounter{chapter}{17}

\begin{document}

%\chapter{Paragraph Shape}\label{par:shape}
%\index{paragraph!shape|(}
\chapter{段落形状}\label{par:shape}
\index{paragraph!shape|(}

%This chapter discusses the parameters and commands that influence the
%shape of a paragraph.
本章讨论影响段落形状的参数和命令。

%\label{cschap:parindent2}\label{cschap:hsize2}\label{cschap:leftskip}\label{cschap:rightskip}\label{cschap:hangindent}\label{cschap:hangafter}\label{cschap:parshape}
%\begin{inventory}
%\item [\cs{parindent}] 
%      Width of the indentation box added in front of a paragraph.
%      Plain \TeX\ default:~\n{20pt}.
\label{cschap:parindent2}\label{cschap:hsize2}\label{cschap:leftskip}\label{cschap:rightskip}\label{cschap:hangindent}\label{cschap:hangafter}\label{cschap:parshape}
\begin{inventory}
\item [\cs{parindent}] 
      在段落开头添加的缩进盒子的宽度。Plain \TeX\ 默认为~\n{20pt}。

%\item [\cs{hsize}] 
%      Line width used for typesetting a paragraph.
%      Plain \TeX\ default:~\n{6.5in}.
\item [\cs{hsize}] 
      段落排版所用的行宽。Plain \TeX\ 默认为~\n{6.5in}。

%\item [\cs{leftskip}] 
%      Glue that is placed to the left of all lines of a paragraph.
\item [\cs{leftskip}] 
      放在段落各行左侧的粘连。


%\item [\cs{rightskip}] 
%      Glue that is placed to the right of all lines of a paragraph.
\item [\cs{rightskip}] 
      放在段落各行右侧的粘连。


%\item [\cs{hangindent}]   
%      If positive, this indicates indentation from the left margin; 
%      if negative, this is the negative of the indentation 
%      from the right margin.
\item [\cs{hangindent}]   
      若大于零，表示左侧的缩进量；若小于零，表示右侧缩进量的负值。

%\item [\cs{hangafter}]   
%      If positive, this denotes the number of lines 
%      before indenting starts; 
%      if negative, the absolute value of this is the number 
%      of indented lines starting with the first line of the paragraph.
%      Default:~\n1.
\item [\cs{hangafter}]   
      若大于零，表示仅不缩进段落的前面多少行；若小于零，其绝对值表示仅缩进段落的前面多少行。
      默认值为~\n1。

%\item [\cs{parshape}]
%      Command for general paragraph shapes.
\item [\cs{parshape}]
      用于设定段落形状的一般命令。

%\end{inventory}
\end{inventory}


%\begin{figure}[ht]
%  \input figs20
%\end{figure}
\begin{figure}[ht]
  \input figs20
\end{figure}

%%\point The width of text lines
%\section{The width of text lines}
%\index{line!width|(}
%\point The width of text lines
\section{文本行的宽度}
\index{line!width|(}

%When \TeX\ has finished absorbing a paragraph, 
%it has formed a horizontal list, starting with an indentation
%box, and ending with \cs{parfillskip} glue.
%This list is then broken into lines of length \cs{hsize}.
%\cstoidx hsize\par\cstoidx leftskip\par\cstoidx rightskip\par
%Each line of a paragraph is padded left and right with
%certain amounts of glue, the \cs{leftskip} and \cs{rightskip},
%which are taken into account in reaching \cs{hsize}.
在吸收完一个段落后，\TeX\ 形成了一个以缩进盒子开头，
以 \cs{parfillskip} 粘连结尾的水平列，然后将此列表分为长度相等的多行。
\cstoidx hsize\par\cstoidx leftskip\par\cstoidx rightskip\par
段落各行的宽度等于 \cs{hsize}，其中包括两侧填充的 \cs{leftskip} 和
\cs{rightskip} 粘连。

%The values of \cs{leftskip} and \cs{rightskip} are taken 
%into account in the line-breaking algorithm.
%Thus the main point about the \csidx{raggedright} 
%macro in plain \TeX\ and the \LaTeX\ `flushleft'
%environment is that they
%set the \cs{rightskip} to  zero plus some stretch.
\TeX\ 的断行算法将 \cs{leftskip} 和 \cs{rightskip} 的值考虑在内。
而 plain \TeX\ 的 \csidx{raggedright} 宏与 \LaTeX\ 的 `flushleft'
环境的要点就在于，将 \cs{rightskip} 设定为零加上某些伸长量。

%The commands \cs{parshape} and \cs{hangindent}
%also affect line width. They work by altering the
%\cs{hsize} and afterwards shifting the boxes 
%containing the lines.
命令 \cs{parshape} 和 \cs{hangindent} 也影响行宽。
它们通过改变 \cs{hsize} 然后移动文本行所在盒子来实现。

%\index{line!width|)}
\index{line!width|)}

%%\point Shape parameters
%\section{Shape parameters}
%\point Shape parameters
\section{段落形状参数}

%%\spoint Hanging indentation
%\subsection{Hanging indentation}
%\index{indentation!hanging|(}
%\spoint Hanging indentation
\subsection{悬挂缩进}
\index{indentation!hanging|(}

%\message{twolines?}
%A simple, and frequently occurring, paragraph shape is that
%\cstoidx hangafter\par\cstoidx hangindent\par
%with a number of starting or trailing lines indented.
%\TeX\ can realize such shapes using two parameters:
%\cs{hangafter} and \cs{hangindent}.
%Both can assume positive and negative values.
\message{twolines?}
有种简单而常见的段落形状是开头或结尾若干行缩进。
\cstoidx hangafter\par\cstoidx hangindent\par
\TeX\ 用 \cs{hangafter} 和 \cs{hangindent} 这两个参数实现这种形状。
这两者都可以设定为正值或负值。

%The \cs{hangindent} controls the amount of indentation:
%\begin{itemize}\item \cs{hangindent}${}>0$: the paragraph
%is indented at the left margin by this amount.
%\item\cs{hangindent}${}<0$: the paragraph is indented
%at the right margin by the absolute value of this amount.
%\end{itemize}
%\def\exnul{\leftskip=0pt \rightskip=0pt \relax}
%For example (assume \cs{parindent=0pt}),
%\begin{disp}\leavevmode\message{Check parshape example!}%
%\hbox{%\Distance:verbatimwhiteleft=0pt
%$\vcenter{\hsize=3.5in \snugbox{\begin{verbatim}
% a a a a a a a a a a a a ...
%
% \hangindent=10pt
% a a a a a a a a a a a a ...
%
% \hangindent=-10pt
% a a a a a a a a a a a a ...
%\end{verbatim}
%}}$\quad gives\quad\quad
%$\vcenter{\parindent0pt \setbox0\hbox{a a a a a}\hsize\wd0
% \leftskip=0pt %\parskip6pt 
% a a a a a a a a a a a a \dots\par%\vskip\baselineskip
% \hangindent=10pt
% a a a a a a a a a a a a \dots\par%\vskip\baselineskip
% \hangindent=-10pt
% a a a a a a a a a a a a \dots\par}$
%}\end{disp}
%The default value of \cs{hangindent} is~\n{0pt}.
\cs{hangindent} 控制缩进量的大小：
\begin{itemize}\item \cs{hangindent}${}>0$：段落根据它的大小在左侧缩进。
\item\cs{hangindent}${}<0$：段落根据它的绝对值的大小在右侧缩进。
\end{itemize}
\def\exnul{\leftskip=0pt \rightskip=0pt \relax}
举个例子（假设 \cs{parindent=0pt}），
\begin{disp}\leavevmode\message{Check parshape example!}%
\hbox{%\Distance:verbatimwhiteleft=0pt
$\vcenter{\hsize=2.7in \snugbox{\begin{verbatim}
a a a a a a a a a a a a ...

\hangindent=10pt
a a a a a a a a a a a a ...

\hangindent=-10pt
a a a a a a a a a a a a ...
\end{verbatim}
}}$\quad 给出\quad\quad
$\vcenter{\parindent0pt \setbox0\hbox{a a a a a}\hsize\wd0
 \leftskip=0pt %\parskip6pt 
 a a a a a a a a a a a a \dots\par%\vskip\baselineskip
 \hangindent=10pt
 a a a a a a a a a a a a \dots\par%\vskip\baselineskip
 \hangindent=-10pt
 a a a a a a a a a a a a \dots\par}$
}\end{disp}
\cs{hangindent} 的默认值为~\n{0pt}。

%The \cs{hangafter} parameter determines the number of
%lines that is indented:
%\begin{itemize}\item \cs{hangafter}${}\geq0$: 
%after this number of lines the rest of the lines will be
%indented; in other words, this many lines from the
%start of the paragraph will not be indented.
%\item \cs{hangafter}${}<0$: the absolute value of this
%is the number of lines that will be indented starting
%at the beginning of the paragraph.\end{itemize}
%For example,
%\message{check left align}
%\begin{disp}\leavevmode\hbox{%\Distance:verbatimwhiteleft=0pt
%$\vcenter{\hsize=3.5in \snugbox{\begin{verbatim}
% a a a a a a a a a a a a ...
%
% \hangindent=10pt \hangafter=2
% a a a a a a a a a a a a ...
%
% \hangindent=10pt \hangafter=-2
% a a a a a a a a a a a a ...
%\end{verbatim}
%}}$\quad looks like\quad\quad
%$\vcenter{\parindent0pt \setbox0\hbox{a a a a a}\hsize\wd0
% \leftskip=0pt %\parskip6pt
% a a a a a a a a a a a a \dots\par%\vskip\baselineskip
% \hangindent=10pt \hangafter=2
% a a a a a a a a a a a a \dots\par%\vskip\baselineskip
% \hangindent=10pt \hangafter=-2
% a a a a a a a a a a a a \dots\par}$
%}\end{disp}
\cs{hangafter} 参数确定需要缩进的行的数目：
\begin{itemize}
\item \cs{hangafter}${}\geq0$：
这么多行除外的其他行都被缩进；也就是说，段落开头的这么多行将不会被缩进。
\item \cs{hangafter}${}<0$：它的绝对值就是段落开头将被缩进的行的数目。
\end{itemize}
举个例子，
\message{check left align}
\begin{disp}\leavevmode\hbox{%\Distance:verbatimwhiteleft=0pt
$\vcenter{\hsize=2.8in \snugbox{\begin{verbatim}
a a a a a a a a a a a a ...

\hangindent=10pt \hangafter=2
a a a a a a a a a a a a ...

\hangindent=10pt \hangafter=-2
a a a a a a a a a a a a ...
\end{verbatim}
}}$\quad 给出\quad\quad
$\vcenter{\parindent0pt \setbox0\hbox{a a a a a}\hsize\wd0
 \leftskip=0pt %\parskip6pt
 a a a a a a a a a a a a \dots\par%\vskip\baselineskip
 \hangindent=10pt \hangafter=2
 a a a a a a a a a a a a \dots\par%\vskip\baselineskip
 \hangindent=10pt \hangafter=-2
 a a a a a a a a a a a a \dots\par}$
}\end{disp}
%The default value for \cs{hangafter} is~\n1.
\cs{hangafter} 的默认值为~\n1。

%With both parameters having the possibility to
%be positive and negative,
%four ways of hanging indentation result. See below
%for hanging indentation into the margin (`outdent').
这两个参数都可正可负，总共有四种悬挂缩进结果。
下面还将介绍探出边界的悬挂缩进（`outdent'）。

%Hanging indentation is implemented as follows.
%The amount of hanging indentation is subtracted
%from the \cs{hsize} for the lines that indent;
%after the paragraph has been broken into horizontal
%boxes, the lines that should indent on the left are
%shifted right.
悬挂缩进是这样实现的：先从缩进行的 \cs{hsize} 中减去缩进量，
接着将段落分段为行，然后往右移动那些左侧缩进行。

%Regular indentation of size \cs{parindent} is not
%influenced by hanging indentation. Thus you should
%start a paragraph with hanging indentation 
%explicitly by~\cs{noindent} if the extra
%indentation is unwanted.
正常的 \cs{parindent} 缩进不受悬挂缩进影响。
如果不想要这个多余缩进，你应该在悬挂缩进段落开头使用 \cs{noindent}。

%The default values of \cs{hangindent} and \cs{hangafter} are
%restored after every \cs{par} command.
在每个 \cs{par} 命令之后 \cs{hangindent} 和 \cs{hangafter} 被还原为它们的默认值。

%\index{indentation!hanging|)}
\index{indentation!hanging|)}

%\subsection{General paragraph shapes: \cs{parshape}}
\subsection{一般形状}

%Quite general paragraph shapes can be implemented
%using \csidx{parshape}. With this command line lengths and indentation
%for the first $n$ lines
%of a paragraph can be specified. Thus this command
%takes $2n+1$ parameters: the number of lines $n$, followed
%by $n$ pairs of an indentation   and a line length.
%\begin{disp} \cs{parshape}\gr{equals}
%    $n$ $i_1$ $\ell_1$ $\ldots$ $i_n$ $\ell_n$\end{disp}
%The   specification for the last line is repeated if the
%paragraph following has more than $n$ lines. If there are fewer
%than $n$ lines the remaining specifications are ignored.
%The default value is (naturally) \cs{parshape${}={}$0}.
用 \csidx{parshape} 可以实现很一般的段落形状。
这个命令可以指定段落前 $n$ 行的缩进量和行宽，因此它有 $2n+1$ 个参数：
先是行数 $n$，接着是 $n$ 对缩进量和行宽。
\begin{disp} \cs{parshape}\gr{equals}
    $n$ $i_1$ $\ell_1$ $\ldots$ $i_n$ $\ell_n$\end{disp}
如果段落超过 $n$ 行，剩下的各行将重复第$n$行的指定。
如果段落少于 $n$ 行，多余的指定将被忽略。
默认值（当然）是 \cs{parshape${}={}$0}。

%A \cs{parshape} command takes precedence over a \cs{hangindent}
%if both have been specified. 
%%Regular \cs{parindent} indentation
%%is suppressed if \cs{parshape} is in effect.
%Regular \cs{parindent}, \cs{leftskip}, 
%and \cs{rightskip} are still obeyed if \cs{parshape} is in effect.
如果两者同时给出，那么 \TeX 执行 \cs{parshape} 命令而忽略掉 \cs{hangindent}。
%Regular \cs{parindent} indentation
%is suppressed if \cs{parshape} is in effect.
在 \cs{parshape} 生效时，原本的 \cs{parindent}、\cs{leftskip} 和
\cs{rightskip} 仍然有效。

%The \cs{parshape} parameter is, like \cs{hangindent}, \cs{hangafter},
%and \cs{looseness} (see Chapter~\ref{line:break}),
%cleared after a \cs{par}
%command. Since every empty line generates a \cs{par} token,
%one should not leave an empty line
%between a paragraph shape (or hanging indentation)
%declaration and the following paragraph.
如同 \cs{hangindent}、\cs{hangafter} 和 \cs{looseness} 命令，
\cs{parshape}参数也会在 \cs{par} 命令后被重置（见第~\ref{line:break}~章）。
由于每个空行生成一个 \cs{par} 记号，
在段落形状（或悬挂缩进）定义和段落内容之间你不应该留下空行。

%The control sequence
%\alt
%\cs{parshape} is an \gr{internal integer}:
%its value is the number of lines $n$ with which
%it was set.
控制序列
\alt
\cs{parshape} 是一个 \gr{internal integer}：
它的值等于所设定的行数 $n$。

%%\point Assorted remarks
%\section{Assorted remarks}
%\point Assorted remarks
\section{杂项注记}

%%\spoint Centred last lines
%\subsection{Centred last lines}
%\spoint Centred last lines
\subsection{末尾行居中}

%Equal stretch and shrink amounts for the \cs{leftskip} and 
%\cs{rightskip}
%give centred texts, in the sense that each line is
%centred. 
%For proper centring of the first
%and last lines of a paragraph the \cs{parindent} and
%\cs{parfillskip} have to be made zero.
%However, the margins are ragged.
给 \cs{leftskip} 和 \cs{rightskip} 设定相等的伸长量和收缩量将给出居中文本，
在各行都居中的意义上。要让段落首行和尾行真正地居中，
必须将 \cs{parindent} 和 \cs{parfillskip} 都设定为零。
然而，两侧边界是不对齐的。

%A surprising application of \cs{leftskip} and \cs{rightskip}
%\mdqon
%\howto Centre the first/""last line of a paragraph\par
%\mdqoff
%leads to paragraphs with flush margins and a centred
%last line.
%\begin{verbatim}
%\leftskip=0cm plus 0.5fil \rightskip=0cm plus -0.5fil
%\parfillskip=0cm plus 1fil
%\end{verbatim}
出人意料地，\cs{leftskip} 和 \cs{rightskip}
\mdqon
\howto Centre the first/""last line of a paragraph\par
\mdqoff
可以让段落两侧对齐而末尾行居中：
\begin{verbatim}
\leftskip=0cm plus 0.5fil \rightskip=0cm plus -0.5fil
\parfillskip=0cm plus 1fil
\end{verbatim}
%For all lines of a paragraph but the 
%last one the stretch components
%add up to zero so the \cs{leftskip} and \cs{rightskip}
%inserted are zero.
%On the last line the \cs{parfillskip} adds \hbox{\n{plus 1fil}}
%of stretch; therefore there is a total of
%\hbox{\n{plus 0.5fil}} of stretch at both the left and right
%end of the line.
在段落的非末尾行，伸长量加起来等于零，
所以插入的 \cs{leftskip} 和 \cs{rightskip} 等于零。
而在末尾行，\cs{parfillskip} 添加了 \hbox{\n{plus 1fil}} 的伸长量；
因此左右两边的总伸长量都是 \hbox{\n{plus 0.5fil}}。

%It would have been incorrect to specify
%\begin{verbatim}
%\leftskip=0cm plus 0.5fil \rightskip=0cm minus 0.5fil
%\end{verbatim}
%\TeX\ gives an error about this: it complains about
%`infinite shrinkage'.
如果这样写将会是错误的：
\begin{verbatim}
\leftskip=0cm plus 0.5fil \rightskip=0cm minus 0.5fil
\end{verbatim}
对此 \TeX\ 将给出一个错误：它抱怨 `infinite shrinkage'。
%%【译注】完整的错误信息如下：
%%! Infinite glue shrinkage found in a paragraph.
%%
%%The paragraph just ended includes some glue that has
%%infinite shrinkability, e.g., `\hskip 0pt minus 1fil'.
%%Such glue doesn't belong there---it allows a paragraph
%%of any length to fit on one line. But it's safe to proceed,
%%since the offensive shrinkability has been made finite.

%Centring not only the last line, but also the
%first line of a paragraph can be done by
%the parameter settings
%\begin{verbatim}
%\parindent=0pt \everypar{\hskip 0pt plus -1fil}
%\leftskip=0pt plus .5fil
%\rightskip=0pt plus -.5fil
%\end{verbatim}
%This time a horizontal skip inserted by \cs{everypar}
%combines with the \cs{leftskip} to give the same
%amount of stretchability on both sides of the
%first line of the paragraph.
要让首行和尾行一样居中，可以用下面的参数设定：
\begin{verbatim}
\parindent=0pt \everypar{\hskip 0pt plus -1fil}
\leftskip=0pt plus .5fil
\rightskip=0pt plus -.5fil
\end{verbatim}
此时用 \cs{everypar} 插入的水平间距和 \cs{leftskip}
间距合起来将使得段落首行两侧的伸展能力相同。

%%\spoint Indenting into the margin
%\subsection{Indenting into the margin}
%\spoint Indenting into the margin
\subsection{凸出边界}

%Suppose you want a hanging indent of \n{1cm} {\sl into\/}
%\howto Indent into the margin\par
%the left margin after the first two lines of a paragraph. 
%Specifying \verb/\hangindent=-1cm/ will give
%a hanging indentation of one centimetre from the {\sl right\/}
%margin, so another approach is necessary. The following does the
%job:
%\begin{verbatim}
% \leftskip=-1cm \hangindent=1cm \hangafter=-2
%\end{verbatim}
%The only problem with this is that
%the leftskip needs to be reset after the paragraph.
%Suitable redefinition of \cs{par} removes this objection:
%\begin{verbatim}
%\def\hangintomargin{\bgroup
%    \leftskip=-1cm \hangindent=1cm \hangafter=-2
%    \def\par{\endgraf\egroup}}
%\end{verbatim}
%The redefinition of \cs{par} is here local to the paragraph that
%should be outdented.
假设你想要的悬挂缩进是让段落第二行以后各行{\sl 凸出\/}左边界 \n{1cm}。
\howto Indent into the margin\par
设定 \verb/\hangindent=-1cm/ 将得到在{\sl 右边界\/}缩进 \n{1cm} 的悬挂缩进，
所以需要另想办法。下面的方法可以完成此任务：
\begin{verbatim}
 \leftskip=-1cm \hangindent=1cm \hangafter=-2
\end{verbatim}
此方法的唯一问题在于段落结束后需要重设 \cs{leftskip}。
我们可以通过重定义 \cs{par} 解决此问题：
\begin{verbatim}
\def\hangintomargin{\bgroup
    \leftskip=-1cm \hangindent=1cm \hangafter=-2
    \def\par{\endgraf\egroup}}
\end{verbatim}
这里对 \cs{par} 的重定义是局部的，只对需要凸出的段落生效。

%Another, elegant, solution uses \cs{parshape}:
%\begin{verbatim}
% 
%\dimen0=\hsize \advance\dimen0 by 1cm
%\parshape=3        % three lines:
%    0cm\hsize      % first  line specification
%    0cm\hsize      % second line specification
%    -1cm\dimen0    % third  line specification
%\end{verbatim}
还有一种更简洁的做法是利用 \cs{parshape}：
\begin{verbatim}
\dimen0=\hsize \advance\dimen0 by 1cm
\parshape=3        % three lines:
    0cm\hsize      % first  line specification
    0cm\hsize      % second line specification
    -1cm\dimen0    % third  line specification
\end{verbatim}

%%\spoint Hang a paragraph from an object
%\subsection{Hang a paragraph from an object}
%\spoint Hang a paragraph from an object
\subsection{悬挂在对象上}

%The \LaTeX\ format has a macro, \cs{@hangfrom}, to have
%\howto Hang a paragraph from an object\par
%one paragraph of text hanging from some object, usually a box
%or a short line of text. 
\LaTeX\ 格式有一个 \cs{@hangfrom} 宏，
\howto Hang a paragraph from an object\par
用于将整个段落的文本悬挂在某个对象上，此对象通常是盒子或短文本。

%\begingroup
%\medskip
%\def\hangobject{Example \ }
%\setbox0=\hbox{\hangobject}
%\hangindent \wd0 \noindent \hangobject
%This paragraph is an example of the \cs{hangfrom} macro
%defined below.
%In the \LaTeX\ document
%styles, the \cs{@hangfrom} macro (which is similar to this)
%is used for multi-line section headings.\par
%\endgroup
\begingroup
\medskip
\def\hangobject{悬挂例子 \ }
\setbox0=\hbox{\hangobject}
\hangindent \wd0 \noindent \hangobject
这个段落是下面定义的 \cs{hangfrom} 宏的一个例子。在 \LaTeX\ 文档类中，
有一个 \cs{@hangfrom} 宏（与这里定义的类似）用于排版多行节标题。\par
\endgroup

%Consider then the macro \cs{hangfrom}:
%\begin{verbatim}
% 
%\def\hangfrom#1{\def\hangobject{#1}\setbox0=\hbox{\hangobject}%
%    \hangindent \wd0 \noindent \hangobject \ignorespaces}
%\end{verbatim}
%Because of the default \cs{hangafter=1}, this 
%will produce one line of width \cs{hsize}, after which the
%rest of the paragraph will be left indented  by the width of the
%\cs{hangobject}.
现在来看 \cs{hangfrom} 宏的定义：
\begin{verbatim}
 
\def\hangfrom#1{\def\hangobject{#1}\setbox0=\hbox{\hangobject}%
    \hangindent \wd0 \noindent \hangobject \ignorespaces}
\end{verbatim}
由于默认情形 \cs{hangafter=1}，这将使得段落首行的宽度为 \cs{hsize}，
而后面各行按照 \cs{hangobject} 的宽度左缩进。

%%\spoint Another approach to hanging indentation
%\subsection{Another approach to hanging indentation}
%\spoint Another approach to hanging indentation
\subsection{另一种悬挂缩进方法}

%Hanging indentation can also be attained by a combination
%of shifting the left margin and outdenting.
%Itemized lists can for instance be implemented in this manner:
%\begin{verbatim}
%\newdimen\listindent
%\def\itemize{\begingroup
%    \advance\leftskip by \listindent
%    \parindent=-\listindent}
%\def\stopitemize{\par\endgroup}
%\def\item#1{\par\leavevmode
%    \hbox to \listindent{#1\hfil}\ignorespaces
%    }
%\end{verbatim}
%If an item should encompass more than one paragraph, the
%implementation could be
%\begin{verbatim}
%\newdimen\listindent \newdimen\listparindent
%\def\itemize{\begingroup
%    \advance\leftskip by \listindent
%    \parindent=\listparindent}
%\def\stopitemize{\par\endgroup}
%\def\item#1{\par\noindent
%    \hbox to 0cm{\kern-\listindent #1\hfil}\ignorespaces
%    }
%\end{verbatim}
将移动边界和凸出边界结合起来也可以得到悬挂缩进。
比如逐项列表就可以用这种方式实现：
\begin{verbatim}
\newdimen\listindent
\def\itemize{\begingroup
    \advance\leftskip by \listindent
    \parindent=-\listindent}
\def\stopitemize{\par\endgroup}
\def\item#1{\par\leavevmode
    \hbox to \listindent{#1\hfil}\ignorespaces
    }
\end{verbatim}
若想让列表项包含多个段落，可以这样实现：
\begin{verbatim}
\newdimen\listindent \newdimen\listparindent
\def\itemize{\begingroup
    \advance\leftskip by \listindent
    \parindent=\listparindent}
\def\stopitemize{\par\endgroup}
\def\item#1{\par\noindent
    \hbox to 0cm{\kern-\listindent #1\hfil}\ignorespaces
    }
\end{verbatim}

%\begin{example}
%\begin{verbatim}
%\itemize\item{1.}First item\par
%Is two paragraphs long.
%\item{2.}Second item.\stopitemize
%\end{verbatim}
%gives
%\begin{disp}
%\def\itemize{\begingroup
%    \advance\leftskip by \parindent
%    \parindent=1em\relax}
%\def\stopitemize{\par\endgroup}
%\def\item#1{\par\noindent
%    \hbox to 0cm{\kern-\parindent #1\hfil}\ignorespaces
%    }
%\itemize\item{1.}First item\par
%Is two paragraphs long.
%\item{2.}Second item.\stopitemize
%\end{disp}
%\end{example}
\begin{example}
\begin{verbatim}
\itemize\item{1.}First item\par
Is two paragraphs long.
\item{2.}Second item.\stopitemize
\end{verbatim}
给出
\begin{disp}
\def\itemize{\begingroup
    \advance\leftskip by \parindent
    \parindent=1em\relax}
\def\stopitemize{\par\endgroup}
\def\item#1{\par\noindent
    \hbox to 0cm{\kern-\parindent #1\hfil}\ignorespaces
    }
\itemize\item{1.}First item\par
Is two paragraphs long.
\item{2.}Second item.\stopitemize
\end{disp}
\end{example}

%%\spoint Hanging indentation versus \cs{leftskip} shifting
%\subsection{Hanging indentation versus \cs{leftskip} shifting}
%\spoint Hanging indentation versus \cs{leftskip} shifting
\subsection{悬挂缩进对比边界移动}

%From the above examples it would seem that
%hanging indentation and modifying the \cs{leftskip} and \cs{rightskip}
%are interchangeable. They are, but only to a certain   extent.
%\altt
上面的例子似乎表明悬挂缩进与修改 \cs{leftskip} 和 \cs{rightskip} 是可互换的。
它们确实可以，但只在一定程度上。
\altt

%Setting \cs{leftskip} to some positive value for a paragraph
%means that the \cs{hsize} stays the same, but every line
%starts with a glue item. Hanging indentation, on the other hand,
%is implemented by decreasing the \cs{hsize} value for the
%lines that hang, and shifting the finished 
%horizontal boxes horizontally in the surrounding vertical list.
将段落的 \cs{leftskip} 设为某个正值意味着 \cs{hsize} 保持不变，
但各行都以一个粘连项开始。另一方面，悬挂缩进是通过减少缩进行的
\cs{hsize} 值，然后在竖直列中移动水平盒子实现的。

%The difference between the two approaches becomes visible
%mainly in the fact that display formulas are not shifted
%when the \cs{leftskip} is altered.
%See Chapter~\ref{rules} for an example showing how leaders
%are affected by margin shifting.
这两种方法的区别可以从这个事实中看到：改变 \cs{leftskip} 并不会移动陈列公式。
见第~\ref{rules}~章中展示的指引线如何受边界移动影响的例子。

%%\spoint More examples
%\subsection{More examples}
%\spoint More examples
\subsection{更多例子}

%Some more examples of paragraph shapes (effected by
%various means) can be found in~\cite{E1}. One example
%from that article appears on page~\pageref{varioset}.
段落形状（用各种方式修改）的更多例子可以在~\cite{E1}~中找到。
第~\pageref{varioset}~页的一个例子就取自该文章。

%\index{paragraph!shape|)}
%\endofchapter
\index{paragraph!shape|)}
\endofchapter

\end{document}