\mapsto 等同于 \rightrightarrows？

Question

命令\rightrightarrows(的amsfonts) 垂直堆叠两个\to/ \rightarrow，是否有等效命令可以堆叠两个\mapsto？如果没有，如何定义它以与 的定义一致\rightrightarrows？

Answer 1

实际上并\mapstochar不允许将两个字符堆叠得像\rightrightarrows

\documentclass{article}

\usepackage{amsmath} % for scalable \fontdimen8
\usepackage{amssymb} % for comparison with \rightrightarrow
\usepackage[old]{old-arrows} % for smaller arrow heads

\makeatletter
\newcommand{\mapsmapsto}{\mathpalette\@mapsmapsto\relax}
\newcommand*{\@mapsmapsto}[2]{%
   \dimen@\fontdimen8
       \ifx#1\displaystyle\textfont\else
       \ifx#1\textstyle\textfont\else
       \ifx#1\scriptstyle\scriptfont\else
       \scriptscriptfont\fi\fi\fi 3
   \mathrel{%
      \vcenter{%
         \vbox{%
            \baselineskip\z@skip
            \lineskip\z@
            \ialign{##\cr$#1\mapstochar\varrightarrow$\cr
            \noalign{\kern\dimen@}%
            $#1\mapstochar\varrightarrow$\cr}%
         }%
      }%
   }%
}
\makeatother

\begin{document}

$A \rightrightarrows B \mapsmapsto C$

$\scriptstyle A \rightrightarrows B \mapsmapsto C$

$\scriptscriptstyle A \rightrightarrows B \mapsmapsto C$

\end{document}

评论：

• 整个\fontdimen内容分配给\dimen@分数规则的厚度。使用此包，amsmath这将根据当前的数学样式进行缩放。
• 该软件包-old-arrows提供了“旧式”箭头。加载此选项后，old它不会替换标准定义，而是定义\var...现有箭头的一个版本。

如果你不介意两个垂直笔划几乎互相接触，你可以删除整个\fontdimen东西和包含的行\noalign

\newcommand*{\@mapsmapsto}[2]{%
    \mathrel{%
      \vcenter{%
         \vbox{%
            \baselineskip\z@skip
            \lineskip\z@
            \ialign{##\cr$#1\mapstochar\varrightarrow$\cr
            $#1\mapstochar\varrightarrow$\cr}%
         }%
      }%
   }%
}

获取

Answer 2

毕竟这就是我正在使用的。本质上，我使用 campa 的模板重新定义\tto以保持一致性，并定义了两个符号的长版本。

\usepackage{amsmath}
\usepackage{amssymb}
\usepackage[old]{old-arrows}

\makeatletter
\renewcommand{\tto}{\mathpalette\@tto\relax}
\newcommand*{\@tto}[2]{%
   \dimen@\fontdimen8
       \ifx#1\displaystyle\textfont\else
       \ifx#1\textstyle\textfont\else
       \ifx#1\scriptstyle\scriptfont\else
       \scriptscriptfont\fi\fi\fi 3
   \mathrel{%
      \vcenter{%
         \vbox{%
            \baselineskip\z@skip
            \lineskip\z@
            \ialign{##\cr$#1\varrightarrow$\cr
            \noalign{\kern-\dimen@}%
            $#1\varrightarrow$\cr}%
         }%
      }%
   }%
}

\makeatletter
\newcommand{\longtto}{\mathpalette\@longtto\relax}
\newcommand*{\@longtto}[2]{%
   \dimen@\fontdimen8
       \ifx#1\displaystyle\textfont\else
       \ifx#1\textstyle\textfont\else
       \ifx#1\scriptstyle\scriptfont\else
       \scriptscriptfont\fi\fi\fi 3
   \mathrel{%
      \vcenter{%
         \vbox{%
            \baselineskip\z@skip
            \lineskip\z@
            \ialign{##\cr$#1\varlongrightarrow$\cr
            \noalign{\kern-\dimen@}%
            $#1\varlongrightarrow$\cr}%
         }%
      }%
   }%
}

\makeatletter
\newcommand{\mapstto}{\mathpalette\@mapstto\relax}
\newcommand*{\@mapstto}[2]{%
   \dimen@\fontdimen8
       \ifx#1\displaystyle\textfont\else
       \ifx#1\textstyle\textfont\else
       \ifx#1\scriptstyle\scriptfont\else
       \scriptscriptfont\fi\fi\fi 3
   \mathrel{%
      \vcenter{%
         \vbox{%
            \baselineskip\z@skip
            \lineskip\z@
            \ialign{##\cr$#1\mapstochar\varrightarrow$\cr
            \noalign{\kern-\dimen@}%
            $#1\mapstochar\varrightarrow$\cr}%
         }%
      }%
   }%
}

\makeatletter
\newcommand{\longmapstto}{\mathpalette\@longmapstto\relax}
\newcommand*{\@longmapstto}[2]{%
   \dimen@\fontdimen8
       \ifx#1\displaystyle\textfont\else
       \ifx#1\textstyle\textfont\else
       \ifx#1\scriptstyle\scriptfont\else
       \scriptscriptfont\fi\fi\fi 3
   \mathrel{%
      \vcenter{%
         \vbox{%
            \baselineskip\z@skip
            \lineskip\z@
            \ialign{##\cr$#1\mapstochar\varlongrightarrow$\cr
            \noalign{\kern-\dimen@}%
            $#1\mapstochar\varlongrightarrow$\cr}%
         }%
      }%
   }%
}