Plain TeX：使用 \loop 设置 \parshape 参数时出现问题

Question

我试图编写一个宏来将文本环绕在图形周围。我知道它在 Latex 中可用，还有另一个包，figflow for plainTex。我刚刚学会自己写。我的第一步是使用 \parshape 为图形创建一个空白区域。我在这里卡住了。我定义宏如下：

\newcount\ln
\def\wrap#1#2{\parshape=#1 \loop\relax\ifnum\ln<#1 0cm #2 \advance\ln by 1\repeat}

没用。我试过了\edef，也没用。有人能帮忙吗？谢谢！

\parshape{6}{10cm} Here is the definitive guide to the use of TeX, written by the system's creator, Donald E. Knuth. TeX represents the state of the art in computer typesetting. It is particularly valuable where the document, article, or book to be produced contains a lot of mathematics, and where the user is concerned about typographic quality. TeX software offers both writers and publishers the opportunity to produce technical text of all kinds, in an attractive form, with the speed and efficiency of a computer system. Novice and expert users alike will gain from The TeXbook the level of information they seek. Knuth warns newcomers away from the more difficult areas, while he entices experienced users with new challenges. The novice need not learn much about TeX to prepare a simple manuscript with it. But for the preparation of more complex documents, The TeXbook contains all the detail required. Knuth's familiar wit, and illustrations specially drawn by Duane Bibby, add a light touch to an unusually readable software manual. The TeXbook is the first in a five-volume series on Computers and Typesetting, all authored by Knuth
\bye

Answer 1

答案展示了一个非常基本的循环\numexpr。

当您使用\parshape并且只希望特定数量的行受到影响时，您必须添加一个额外的行，以便在完成0cm \hsize后恢复为正常行，因为将对段落的剩余每一行重复最后的规范。\parshape\parshape

\catcode`\@=11
\long\def\@gobble#1{}
\long\def\@secondoftwo#1#2{#2}
\def\wrap#1#2%
  {%
    \parshape=\numexpr#1+1\relax \wrap@{0}{#1}{#2} 0cm \hsize\relax
  }
\def\wrap@#1#2#3%
  {%
    \ifnum#1<#2
      0cm #3
      \expandafter\@secondoftwo
    \fi
    \@gobble{\expandafter\wrap@\expandafter{\the\numexpr#1+1}{#2}{#3}}%
  }
\catcode`\@=12

\wrap{6}{10cm} Here is the definitive guide to the use of TeX, written by the
system's creator, Donald E. Knuth. TeX represents the state of the art in
computer typesetting. It is particularly valuable where the document, article,
or book to be produced contains a lot of mathematics, and where the user is
concerned about typographic quality. TeX software offers both writers and
publishers the opportunity to produce technical text of all kinds, in an
attractive form, with the speed and efficiency of a computer system. Novice and
expert users alike will gain from The TeXbook the level of information they
seek. Knuth warns newcomers away from the more difficult areas, while he entices
experienced users with new challenges. The novice need not learn much about TeX
to prepare a simple manuscript with it. But for the preparation of more complex
documents, The TeXbook contains all the detail required. Knuth's familiar wit,
and illustrations specially drawn by Duane Bibby, add a light touch to an
unusually readable software manual. The TeXbook is the first in a five-volume
series on Computers and Typesetting, all authored by Knuth.
\bye

Answer 2

对于像这样的相对简单的应用程序（缩进仅延伸到一个段落），纯 TeX 提供\hangafter（要缩进的行数，如果从左侧缩进则为正数，如果从右侧缩进则为负数，如这里）和\hangindent（如果缩进从给出的数字之后开始则为正数\hangafter，如果从第 1 行开始则为负数）— 参见 Knuth 的TeXbook，第 102 页。

\hangafter=-6 \hangindent=-6cm
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum. Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.

\bye

为了完整起见，\wrap可以定义一个简单的宏（输出相同）：

\def\wrap#1#2{\hangafter-#1\hangindent-#2}

\wrap{6}{6cm}
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum. Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.

Answer 3

一个简单的可扩展循环expl3；很容易指定所需的特殊线路数量，而不是一次性的。

\input expl3-generic

\ExplSyntaxOn

\cs_new:Npn \wrap #1 #2
 {
  \parshape
    \int_to_arabic:n { #1 + 1 } \c_space_tl % number of special lines
    \prg_replicate:nn { #1 } { 0pt~#2~ } % parameters for the special lines
    0pt~\hsize % further lines
  \ignorespaces
 }

\ExplSyntaxOff

\wrap{6}{10cm} Here is the definitive guide to the use of TeX, written by 
the system's creator, Donald E. Knuth. TeX represents the state of the art 
in computer typesetting. It is particularly valuable where the document, 
article, or book to be produced contains a lot of mathematics, and where 
the user is concerned about typographic quality. TeX software offers both 
writers and publishers the opportunity to produce technical text of all 
kinds, in an attractive form, with the speed and efficiency of a computer 
system. Novice and expert users alike will gain from The TeXbook the level 
of information they seek. Knuth warns newcomers away from the more difficult 
areas, while he entices experienced users with new challenges. The novice 
need not learn much about TeX to prepare a simple manuscript with it. But 
for the preparation of more complex documents, The TeXbook contains all 
the detail required. Knuth's familiar wit, and illustrations specially 
drawn by Duane Bibby, add a light touch to an unusually readable software 
manual. The TeXbook is the first in a five-volume series on Computers and 
Typesetting, all authored by Knuth

\bye

宏\wrap本身是可扩展的，因此你可以这样做

\edef\wrapsix{\wrap{6}{10cm}}

\wrapsix Here is the definitive guide to the use of TeX, written by
the system's creator, Donald E. Knuth. TeX represents the state of the art
in computer typesetting. It is particularly valuable where the document,
article, or book to be produced contains a lot of mathematics, and where
[...]

并在一开始就定义该类的各种形状。

Answer 4

OpTeX 支持扩展\fornum命令，因此另一种方法是在参数\fonrum中使用此命令\parshape。但 OpTeX 不是纯粹的纯 TeX，它是扩展的纯 TeX：

\def\wrap#1#2{\parshape \numexpr#1+1\relax\space \fornum 1..#1\do{0cm#2}0cm\hsize}

\wrap{6}{10cm}\lipsum[1]
\bye