☰

如何修复自定义上划线宏的错误输出？

tag-icon • tag-icon macros math-operators subscripts superscripts
如何修复自定义上划线宏的错误输出？

为了改变垂直位置，\overline我发现了以下宏：

\newcommand*\oline[1]{%
    \vbox{%
        \hrule height 0.5pt%                  % Line above with certain width
        \kern0.4ex%                          % Distance between line and content
        \hbox{%
            \kern-0.1em%                        % Distance between content and left side of box, negative values for lines shorter than content
            \ifmmode#1\else\ensuremath{#1}\fi%  % The content, typeset in dependence of mode
            \kern-0.1em%                        % Distance between content and left side of box, negative values for lines shorter than content
        }% end of hbox
    }% end of vbox
}

但它在上标/下标中效果不好。例如参见以下 MWE：

\documentclass[12pt,a4paper]{article}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\newcommand*\oline[1]{%
    \vbox{%
        \hrule height 0.5pt%                  % Line above with certain width
        \kern0.4ex%                          % Distance between line and content
        \hbox{%
            \kern-0.1em%                        % Distance between content and left side of box, negative values for lines shorter than content
            \ifmmode#1\else\ensuremath{#1}\fi%  % The content, typeset in dependence of mode
            \kern-0.1em%                        % Distance between content and left side of box, negative values for lines shorter than content
        }% end of hbox
    }% end of vbox
}
\begin{document}
    \section{title}
    \[\overline{h},\overline{h_t},\overline{h_{t_1}},\overline{h}_{t_1}\]

    \[\oline{h}, \oline{h_t}, \oline{h_{t_1}}, \oline{h}_{t_1}\]
\end{document}

及其输出：

在此处输入图片描述

如何修复此错误输出\oline？

答案1

不良影响不仅限于下标：

\documentclass[12pt,a4paper]{article}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\newcommand*\oline[1]{%
    \vbox{%
        \hrule height 0.5pt%                  % Line above with certain width
        \kern0.4ex%                          % Distance between line and content
        \hbox{%
            \kern-0.1em%                        % Distance between content and left side of box, negative values for lines shorter than content
            \ifmmode#1\else\ensuremath{#1}\fi%  % The content, typeset in dependence of mode
            \kern-0.1em%                        % Distance between content and left side of box, negative values for lines shorter than content
        }% end of hbox
    }% end of vbox
}
\begin{document}

$a\oline{h}b$

\end{document}

在此处输入图片描述

问题在于您没有取消所应用的负字距，从而欺骗上划线使其比其上方应有的字符更短。

\documentclass[12pt,a4paper]{article}
\usepackage{amsmath}
\usepackage{amssymb}

\newcommand*\oline[1]{%
  \kern0.1em            % Counteract the inner kern
  \vbox{%
    \hrule height 0.5pt % Line above with certain width
    \kern0.4ex          % Distance between line and content
    \hbox{%
      \kern-0.1em       % Shorten the content on the left
      $#1$%             % The content, typeset math mode
      \kern-0.1em       % Shorten the content on the right
    }% end of hbox
  }% end of vbox
  \kern0.1em            % Counteract the inner kern
}

\begin{document}

$a\oline{h}b+\oline{h}_{t}+\oline{h_t}$

$ahb+h_t+h_t$

\end{document}

\ifmmode代码中的条件根本不执行任何操作，因为它出现在模式\hbox为的内部，不是\vboxmath：TeX 在启动 a或 a时不会继承模式\hbox：它分别以内部垂直模式和受限水平模式启动它们。因此，您只需启动数学模式即可。

在此处输入图片描述

紧跟%在pt、ex和em后面的字符是错误的：TeX 会在所需测量单位后寻找（并忽略）空格标记。省略空格可能会导致不合时宜的扩展问题。例如，\ifmmode在实际放置 kern 之前，您的 就已扩展；在这种情况下，这并不是什么问题，因为条件被评估为 false。

相关内容