![字母 i 上的短长音符号](https://linux22.com/image/331449/%E5%AD%97%E6%AF%8D%20i%20%E4%B8%8A%E7%9A%84%E7%9F%AD%E9%95%BF%E9%9F%B3%E7%AC%A6%E5%8F%B7%20.png)
答案1
\vbox{\halign{}}
对于这种特殊情况,您可以使用构造:
\def\macroni{\leavevmode\vbox{\offinterlineskip\ialign{\hfil##\hfil\cr
\vrule height.03em width.25em\cr\noalign{\kern.13em}\i\cr}}}
\let\macronori=\=
\def\=#1{\ifx\i#1\macroni\else\macronori{#1}\fi}
S\=a\={\i}