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在以下情况下，是否有技巧可以减少计数器的数量？

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在以下情况下，是否有技巧可以减少计数器的数量？

我想避免使用\tmp。是否可以在保持相同输出的情况下将其删除？

在此处输入图片描述

% Declare counters.
\newcount\pages% \pages is given so you cannot remove it!
\newcount\x
\newcount\tmp

% Initializing.
\pages=9% Try it for an odd or even integer.
\tmp=\pages
\advance\tmp by 1
\x=1

\loop
    \ifnum\x<\tmp
    \noindent\hfill\the\x
    \advance\x by 1
    \ifnum\x>\pages
        \hfill\null\endgraf
    \else
        \hfill\the\x\hfill\null\endgraf
    \fi
    \advance\x by 1
\repeat

\bye

注意：请不要使用e-TeX扩展，因为我现在正在学习 Knuth 的原始 TeX。

答案1

从 开始\x=0，尽快执行并反转内部条件：

\newcount\pages % \pages is given so you cannot remove it!
\newcount\x

% Initializing.
\pages=9 % Try it for an odd or even integer.
\x=0

\loop
  \ifnum\x<\pages
  \advance\x by 1
  \noindent\hfill\the\x
  \ifnum\x<\pages
    \advance\x by 1
    \hfill\the\x
  \fi
  \hfill\null\endgraf
\repeat

\bye

答案2

在循环结束时简单地测试相等性有什么问题：

% Declare counters.
\newcount\pages% \pages is given so you cannot remove it!
\newcount\x

% Initializing.
\pages=9 % Try it for an odd or even integer.

\x=1 %

\loop
  \ifnum\x=\pages
    \noindent
    \hfill
    \number\x
    \hfill
    \null
    \endgraf
  \fi
  \ifnum\x<\pages
    \noindent
    \hfill
    \number\x
    \advance\x by 1 %
    \hfill
    \number\x
    \hfill
    \null
    \endgraf
    \advance\x by 1 %
\repeat

\bye

（我添加了一些空格以正确终止数字。）

答案3

\tmp您在回答中已经将其删除，这\x也会将其删除。

% Declare counters.
\newcount\pages% \pages is given so you cannot remove it!

% Initializing.
\pages=9% Try it for an odd or even integer.


\def\z#1{%
\ifnum#1<\numexpr\pages+1\relax
    \noindent\hfill#1%
  \ifnum#1=\pages
        \hfill\null\endgraf
    \else
        \hfill\number\numexpr#1+1\hfill\null\endgraf
    \fi
    \expandafter\z\expandafter{\number\numexpr#1+2\expandafter\relax\expandafter}%
\fi}
\z1
\bye

答案4

使用\numexpr\pages+1\relax似乎有效：

代码：

% Declare counters.
\newcount\pages% \pages is given so you cannot remove it!
\newcount\x
%\newcount\tmp

% Initializing.
\pages=9% Try it for an odd or even integer.
%\tmp=\pages
%\advance\tmp by 1
\x=1

\loop
    \ifnum\x<\numexpr\pages+1\relax
    \noindent\hfill\the\x
    \advance\x by 1
    \ifnum\x>\pages
        \hfill\null\endgraf
    \else
        \hfill\the\x\hfill\null\endgraf
    \fi
    \advance\x by 1
\repeat

\bye

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