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在数学模式下解释 unicode ²、³ 等字符

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在数学模式下解释 unicode ²、³ 等字符

简短问题：

是否存在某种字体编码或其他技巧可以让²LaTeX 正确解释 unicode 字符（指数 2），特别是在数学模式下（即将其自动转换为^{2}）？

（对于 ³、⁴、... 也同样如此）

详细理由：

通常，要在数学模式下引入指数，可以使用 ^ 符号，如x^2或e^{i\pi}。我已经使用 LaTeX 几十年了，这感觉很自然。但是，使用我当前的设置，当我x ^ 2在键盘上输入字符时，结果会是两个 unicode 字符x²。

\RequirePackage[utf8]{inputenc}我的个人风格文件开头确实有一个，并且 Unicode 字符通常被正确解释（重音字符等）。

通常我会考虑这个问题并输入x ^ ^ 2结果x^2，但我经常输入得很快，然后不得不返回到产生错误的每行代码LaTeX Error: Command \texttwosuperior unavailable in en。这很烦人。

我可以在编辑器级别实现一种解决方法（我使用 vim，因此添加一个映射将 ² 转换为 ^2 很简单），但我想知道是否有更好的独立于编辑器的方法来处理这个问题。

答案1

ConTeXt 做得对。

\starttext

x²³ and $x²³$

\stoptext

在此处输入图片描述

使用 LaTeX 和 可以实现同样的效果unicode-math。

\documentclass{article}
\usepackage{unicode-math}
\begin{document}
x²³ and $x²³$
\end{document}

在 pdfLaTeX 中，您必须使用newunicodechar重新定义²并³使其具有数学模式感知。

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{textcomp} % for \text...superior
\usepackage{newunicodechar}
\newunicodechar{²}{\ifmmode{}^2\else\texttwosuperior\fi}
\newunicodechar{³}{\ifmmode{}^3\else\textthreesuperior\fi}
\begin{document}
x²³ and $x²³$
\end{document}

在此处输入图片描述

答案2

笔记：这个答案大部分是多余的。你可以unicode-math按照其他答案，如果不适用，请使用我的包unicode-math-input。

以下是原始答案。

如果你想在不导入 Unicode-math 的情况下使用 XeTeX 或 LuaTeX 中的符号（因为它改变输出），可以复制部分 Unicode-math 源代码，并将其放在序言中。

基本思想是将字符定义为活动字符，当反复展开时（“扫描”字符向前，使用\__um_scan_sscript:及其辅助功能）

  • 偷看其右侧的字符（\peek_N_type:TF）
  • 检查它是否是另一个上标/下标字符 ( \prop_get:cxNTF)
  • 如果是，将其推到某处（\l__um_ss_chain_tl）并重复。

请参阅 unicode-math 源代码文档中的“19. Unicode 子标和上标”部分（加拿大运输安全局) 以获得更详细的解释。

另一种方法是做类似下面的事情，其灵感来自于数学模式下宏的实现中的一个想法（例如参见附录 B 第 6 部分“数学宏”→ TeXbook 中的'“一组有趣的转换f'''为的宏”）：f^{\prime\prime\prime}

  • make²扩展为^{2\continuesuperscript}，
  • 然后²³扩展为^{2\continuesuperscript}^{3\continuesuperscript}，
  • 该\continuesuperscript宏使得 ^{2\continuesuperscript}^{3} 等同于^{23}，
  • 此类宏的工作原理是：
    • 吸收以下内容}，
    • f然后对以下标记进行无限扩展（为了根据³需要扩展任何^{3...}标记，请注意，在数学模式下可能丢失空格并不重要），
    • 然后检查以下字符是否是^，
      • 如果是，则删除^，和另一个参数#2，并放回#2\egroup（因此^{2\continuesuperscript}^{34}变成^{234\egroup），
        • 有趣的是，这样做^{2\continuesuperscript}^\bgroup34\egroup会^{2\bgroup\egroup34\egroup变成#2\bgroup如预期，
      • 否则，放回并执行}。

检查以下字符是否^需要不可扩张在非LuaTeX引擎中的实现（使用\futurelet）。

看https://gist.github.com/user202729/9b599cdaec827a0bdf6478fb5729b157 用于概念验证实施。（答案太长了，我无法将其包括在内）

PDFTeX 中也可以使用类似的算法，但需要进行一些调整，因为每个 Unicode 字符（UTF-8 编码）在 PDFTeX 中对应多个标记。（一直向下滚动到下方即可查看概念验证实现）

Unicode 引擎的演示：（回想起来，这是一个丑陋的实现，但我并不特别想重写它）

%! TEX program = xelatex
\documentclass{article}
\usepackage{amssymb}


\ExplSyntaxOn

\prop_new:N \g__um_supers_prop
\prop_new:N \g__um_subs_prop

\cs_generate_variant:Nn \prop_gput:Nnn {Nxn}
\cs_generate_variant:Nn \prop_get:NnNTF {cxNTF}

\cs_new:Nn \__um_char_gmake_mathactive:n
  {
    \tex_global:D \tex_mathcode:D \int_eval:n {#1} = "8000 \scan_stop:
  }

\cs_new:Nn \__um_mathactive_remap:nn
  {
    \group_begin:
      \cs_set_protected:Npn \__um_tmp: {#2}
      \__um_char_gmake_mathactive:n {#1}
      \char_gset_active_eq:nN {#1} \__um_tmp:
    \group_end:
  }

\cs_new:Nn \__um_setup_active_superscript:nn
  {
    \prop_gput:Nxn \g__um_supers_prop { \int_eval:n {#1} } {#2}
    \__um_mathactive_remap:nn {#1}
       {
        \tl_set:Nn \l__um_ss_chain_tl {#2}
        \cs_set_eq:NN \__um_sub_or_super:n \sp
        \tl_set:Nn \l__um_tmpa_tl {supers}
        \__um_scan_sscript:
       }
  }
\cs_new:Nn \__um_setup_active_subscript:nn
  {
    \prop_gput:Nxn \g__um_subs_prop { \int_eval:n {#1} } {#2}
    \__um_mathactive_remap:nn {#1}
      {
        \tl_set:Nn \l__um_ss_chain_tl {#2}
        \cs_set_eq:NN \__um_sub_or_super:n \sb
        \tl_set:Nn \l__um_tmpa_tl {subs}
        \__um_scan_sscript:
      }
  }
\cs_new_protected:Nn \__um_scan_sscript:
  {
    \__um_scan_sscript:TF
      { \__um_scan_sscript: }
      { \__um_sub_or_super:n {\l__um_ss_chain_tl} }
  }
\cs_new_protected:Nn \__um_scan_sscript:TF
  {
    \peek_N_type:TF
      {
        \group_align_safe_begin:
        \__um_scan_sscript_aux:nnN {#1} {#2}
      }
      {#2}
  }
\cs_new_protected:Nn \__um_scan_sscript_aux:nnN
  {
    \tl_set:Nx \l__um_tmpa_key_tl { \tl_to_str:n {#3} }
    \prop_get:cxNTF {g__um_\l__um_tmpa_tl _prop}
      { \int_eval:n { \exp_after:wN ` \l__um_tmpa_key_tl } }
      \l__um_tmpb_tl
      {
        \tl_put_right:NV \l__um_ss_chain_tl \l__um_tmpb_tl
        \group_align_safe_end:
        #1
      }
      { \group_align_safe_end: #2 #3 }
  }
\__um_setup_active_superscript:nn {"2070} {0}
\__um_setup_active_superscript:nn {"00B9} {1}
\__um_setup_active_superscript:nn {"00B2} {2}
\__um_setup_active_superscript:nn {"00B3} {3}
\__um_setup_active_superscript:nn {"2074} {4}
\__um_setup_active_superscript:nn {"2075} {5}
\__um_setup_active_superscript:nn {"2076} {6}
\__um_setup_active_superscript:nn {"2077} {7}
\__um_setup_active_superscript:nn {"2078} {8}
\__um_setup_active_superscript:nn {"2079} {9}
\__um_setup_active_superscript:nn {"207A} {+}
\__um_setup_active_superscript:nn {"207B} {-}
\__um_setup_active_superscript:nn {"207C} {=}
\__um_setup_active_superscript:nn {"207D} {(}
\__um_setup_active_superscript:nn {"207E} {)}
\__um_setup_active_superscript:nn {"1D2C} {A}
\__um_setup_active_superscript:nn {"1D2E} {B}
\__um_setup_active_superscript:nn {"1D30} {D}
\__um_setup_active_superscript:nn {"1D31} {E}
\__um_setup_active_superscript:nn {"1D33} {G}
\__um_setup_active_superscript:nn {"1D34} {H}
\__um_setup_active_superscript:nn {"1D35} {I}
\__um_setup_active_superscript:nn {"1D36} {J}
\__um_setup_active_superscript:nn {"1D37} {K}
\__um_setup_active_superscript:nn {"1D38} {L}
\__um_setup_active_superscript:nn {"1D39} {M}
\__um_setup_active_superscript:nn {"1D3A} {N}
\__um_setup_active_superscript:nn {"1D3C} {O}
\__um_setup_active_superscript:nn {"1D3E} {P}
\__um_setup_active_superscript:nn {"1D3F} {R}
\__um_setup_active_superscript:nn {"1D40} {T}
\__um_setup_active_superscript:nn {"1D41} {U}
\__um_setup_active_superscript:nn {"2C7D} {V}
\__um_setup_active_superscript:nn {"1D42} {W}
\__um_setup_active_superscript:nn {"1D43} {a}
\__um_setup_active_superscript:nn {"1D47} {b}
\__um_setup_active_superscript:nn {"1D9C} {c}
\__um_setup_active_superscript:nn {"1D48} {d}
\__um_setup_active_superscript:nn {"1D49} {e}
\__um_setup_active_superscript:nn {"1DA0} {f}
\__um_setup_active_superscript:nn {"1D4D} {g}
\__um_setup_active_superscript:nn {"02B0} {h}
\__um_setup_active_superscript:nn {"2071} {i}
\__um_setup_active_superscript:nn {"02B2} {j}
\__um_setup_active_superscript:nn {"1D4F} {k}
\__um_setup_active_superscript:nn {"02E1} {l}
\__um_setup_active_superscript:nn {"1D50} {m}
\__um_setup_active_superscript:nn {"207F} {n}
\__um_setup_active_superscript:nn {"1D52} {o}
\__um_setup_active_superscript:nn {"1D56} {p}
\__um_setup_active_superscript:nn {"02B3} {r}
\__um_setup_active_superscript:nn {"02E2} {s}
\__um_setup_active_superscript:nn {"1D57} {t}
\__um_setup_active_superscript:nn {"1D58} {u}
\__um_setup_active_superscript:nn {"1D5B} {v}
\__um_setup_active_superscript:nn {"02B7} {w}
\__um_setup_active_superscript:nn {"02E3} {x}
\__um_setup_active_superscript:nn {"02B8} {y}
\__um_setup_active_superscript:nn {"1DBB} {z}
\__um_setup_active_superscript:nn {"1D5D} {\beta}
\__um_setup_active_superscript:nn {"1D5E} {\gamma}
\__um_setup_active_superscript:nn {"1D5F} {\delta}
\__um_setup_active_superscript:nn {"1D60} {\phi}
\__um_setup_active_superscript:nn {"1D61} {\chi}
\__um_setup_active_superscript:nn {"1DBF} {\theta}
\__um_setup_active_subscript:nn {"2080} {0}
\__um_setup_active_subscript:nn {"2081} {1}
\__um_setup_active_subscript:nn {"2082} {2}
\__um_setup_active_subscript:nn {"2083} {3}
\__um_setup_active_subscript:nn {"2084} {4}
\__um_setup_active_subscript:nn {"2085} {5}
\__um_setup_active_subscript:nn {"2086} {6}
\__um_setup_active_subscript:nn {"2087} {7}
\__um_setup_active_subscript:nn {"2088} {8}
\__um_setup_active_subscript:nn {"2089} {9}
\__um_setup_active_subscript:nn {"208A} {+}
\__um_setup_active_subscript:nn {"208B} {-}
\__um_setup_active_subscript:nn {"208C} {=}
\__um_setup_active_subscript:nn {"208D} {(}
\__um_setup_active_subscript:nn {"208E} {)}
\__um_setup_active_subscript:nn {"2090} {a}
\__um_setup_active_subscript:nn {"2091} {e}
\__um_setup_active_subscript:nn {"2095} {h}
\__um_setup_active_subscript:nn {"1D62} {i}
\__um_setup_active_subscript:nn {"2C7C} {j}
\__um_setup_active_subscript:nn {"2096} {k}
\__um_setup_active_subscript:nn {"2097} {l}
\__um_setup_active_subscript:nn {"2098} {m}
\__um_setup_active_subscript:nn {"2099} {n}
\__um_setup_active_subscript:nn {"2092} {o}
\__um_setup_active_subscript:nn {"209A} {p}
\__um_setup_active_subscript:nn {"1D63} {r}
\__um_setup_active_subscript:nn {"209B} {s}
\__um_setup_active_subscript:nn {"209C} {t}
\__um_setup_active_subscript:nn {"1D64} {u}
\__um_setup_active_subscript:nn {"1D65} {v}
\__um_setup_active_subscript:nn {"2093} {x}
\__um_setup_active_subscript:nn {"1D66} {\beta}
\__um_setup_active_subscript:nn {"1D67} {\gamma}
\__um_setup_active_subscript:nn {"1D68} {\rho}
\__um_setup_active_subscript:nn {"1D69} {\phi}
\__um_setup_active_subscript:nn {"1D6A} {\chi}

\ExplSyntaxOff

\begin{document}

$x²³₄₅ + \mathbb{R} + \varnothing$

\end{document}

输出：

输出图像

如你所见，ℝ 和 ∅ 不受影响。（这是可能的，但要恢复旧符号很复杂，请参阅1 2。另外unicode-math编译起来比较慢）

ucs这是 PDFTeX包的实现。

（警告：该实现极其脆弱，可能会在下一个 UCS 版本中崩溃）

阅读评论以了解更多详细信息。

不建议使用。

这是标准（推荐）编码的版本utf8。

%! TEX program = pdflatex
% vim: ts=2 sw=2 et:
\documentclass[12pt]{article}


%\usepackage[mathletters]{ucs}
%\usepackage[utf8x]{inputenc}
\usepackage[utf8]{inputenc}

\ExplSyntaxOn

% (originally) key: int value (Unicode code point), value: the corresponding (non-sscript) character
% (modified) key: sequence of UTF8,
%   value: either \__um_partial:n or \__um_complete {non-sscript character}


\prop_new:N \g__um_supers_prop
\prop_new:N \g__um_subs_prop

\cs_generate_variant:Nn \prop_gput:Nnn {Nxn}
\cs_generate_variant:Nn \prop_get:NnNTF {cxNTF}

\cs_generate_variant:Nn \exp_args:Nx {c}

\cs_new:Nn \__um_mathactive_remap:nn
  {
    \group_begin:
      % for [utf8]
      \exp_args:Nx \DeclareUnicodeCharacter {\tl_tail:n {#1}} {#2}

      % for [utf8x] (require decimal, briefly mentioned in https://github.com/latex3/latex2e/issues/24)
      %\exp_args:Nx \DeclareUnicodeCharacter {\int_eval:n {#1}} {#2}

      % for [utf8x] with clash (see https://tex.stackexchange.com/a/620231/250119)
      %\exp_args:cx {uc@dclc} {\int_eval:n {#1}} {mathletters} {#2}
    \group_end:
  }

\cs_generate_variant:Nn \int_step_inline:nn {xn}

% #1: property list
% #2: the code point as "AAAA
% #3: the non-sscript corresponding character
\cs_new:Nn \__um_put_prefixes:Nnn
{

  \tl_set:Nx \l__um_utfviii_bytes {\char_to_utfviii_bytes:n {#2}}


  % drop the trailing empty groups (nonexistent bytes)
  \tl_set:Nx \l__um_last_byte {\tl_item:Nn \l__um_utfviii_bytes {-1}}
  \bool_while_do:nn {
    \tl_if_empty_p:N \l__um_last_byte
  } {
    \tl_set:Nx \l__um_utfviii_bytes {\tl_range:Nnn \l__um_utfviii_bytes {1} {-2}}
    \tl_set:Nx \l__um_last_byte {\tl_item:Nn \l__um_utfviii_bytes {-1}}
  }

  \cs_set:Nn \__um_char_generate_as_other:n {
    \char_generate:nn {##1} {12} % 12: other, same as output of \tl_to_str:n
  }

  % convert hex to bytes
  \tl_set:Nx \l__um_utfviii_bytes {
    \tl_map_function:NN \l__um_utfviii_bytes \__um_char_generate_as_other:n
  }


  % iterate through incomplete prefixes and define
  \int_step_inline:xn {\tl_count:N \l__um_utfviii_bytes - 1}
  {
    \prop_gput:Nxn #1 { \tl_range:Nnn \l__um_utfviii_bytes {1} {##1} } {\__um_partial:nnnn}
  }

  % define for the only complete prefix
  \prop_gput:Nxn #1 \l__um_utfviii_bytes {\__um_complete:nnnnn {#3}}
  
}






\cs_new:Nn \__um_setup_active_superscript:nn
  {
    \__um_put_prefixes:Nnn \g__um_supers_prop {#1} {#2}
    \__um_mathactive_remap:nn {#1}
       {
        \tl_set:Nn \l__um_ss_chain_tl {#2}
        \cs_set_eq:NN \__um_sub_or_super:n \sp
        \tl_set:Nn \l__um_tmpa_tl {supers}
        \__um_scan_sscript:
       }
  }
\cs_new:Nn \__um_setup_active_subscript:nn
  {
    \__um_put_prefixes:Nnn \g__um_subs_prop {#1} {#2}
    \__um_mathactive_remap:nn {#1}
      {
        \tl_set:Nn \l__um_ss_chain_tl {#2}
        \cs_set_eq:NN \__um_sub_or_super:n \sb
        \tl_set:Nn \l__um_tmpa_tl {subs}
        \__um_scan_sscript:
      }
  }
\cs_new_protected:Nn \__um_scan_sscript:
  {
    \__um_scan_sscript:nnn
      { \__um_scan_sscript: }  % true (got a new character), keep scanning
      { \__um_sub_or_super:n {\l__um_ss_chain_tl} }  % "typesets what it has collected"
      {}
  }

% #1, #2, #3: same as below
\cs_new_protected:Nn \__um_scan_sscript:nnn
  {
    \peek_N_type:TF
      {
        \group_align_safe_begin:
        \__um_scan_sscript_aux:nnnN {#1} {#2} {#3}
      }
      {
        #2 % execute false code
        #3 % return the partial token
      }
  }

%\cs_generate_variant:Nn \__um_scan_sscript:nnn {nnx}

% #1: true code (if the new token continues the chain, then \tl_put_right:NV it to the chain and execute this)
% #2: false code
% #3: the partial token (must **not** be stringified, in case it's returned later)
% #4: the new token (also not stringified)
\cs_new_protected:Nn \__um_scan_sscript_aux:nnnN
  {
    \tl_set:Nx \l__um_tmpa_key_tl { \tl_to_str:n {#4} }
    \prop_get:cxNTF {g__um_\l__um_tmpa_tl _prop}
      %{ \int_eval:n { \exp_after:wN ` \l__um_tmpa_key_tl } }
      { \tl_to_str:n {#3}  \l__um_tmpa_key_tl }
      \l__um_tmpb_tl
      {
        % if there is, do something depends on the result
        \group_align_safe_end:
        \l__um_tmpb_tl {#1} {#2} {#3} {#4}
      }
      { \group_align_safe_end: #2 #3 #4 }  % execute the false code, then return the non-matching part back
  }


% #1: corresponding non-sscript character
% rest: as above
\cs_new:Nn \__um_complete:nnnnn
  {
    \tl_put_right:Nn \l__um_ss_chain_tl #1
    #2
  }

% 1-4: as __um_scan_sscript_aux:nnnN
\cs_new:Nn \__um_partial:nnnn
  {
    \__um_scan_sscript:nnn {#1} {#2} {#3 #4}
  }


\__um_setup_active_superscript:nn {"2070} {0}
\__um_setup_active_superscript:nn {"00B9} {1}
\__um_setup_active_superscript:nn {"00B2} {2}
\__um_setup_active_superscript:nn {"00B3} {3}
\__um_setup_active_superscript:nn {"2074} {4}
\__um_setup_active_superscript:nn {"2075} {5}
\__um_setup_active_superscript:nn {"2076} {6}
\__um_setup_active_superscript:nn {"2077} {7}
\__um_setup_active_superscript:nn {"2078} {8}
\__um_setup_active_superscript:nn {"2079} {9}
\__um_setup_active_superscript:nn {"207A} {+}
\__um_setup_active_superscript:nn {"207B} {-}
\__um_setup_active_superscript:nn {"207C} {=}
\__um_setup_active_superscript:nn {"207D} {(}
\__um_setup_active_superscript:nn {"207E} {)}
\__um_setup_active_superscript:nn {"1D2C} {A}
\__um_setup_active_superscript:nn {"1D2E} {B}
\__um_setup_active_superscript:nn {"1D30} {D}
\__um_setup_active_superscript:nn {"1D31} {E}
\__um_setup_active_superscript:nn {"1D33} {G}
\__um_setup_active_superscript:nn {"1D34} {H}
\__um_setup_active_superscript:nn {"1D35} {I}
\__um_setup_active_superscript:nn {"1D36} {J}
\__um_setup_active_superscript:nn {"1D37} {K}
\__um_setup_active_superscript:nn {"1D38} {L}
\__um_setup_active_superscript:nn {"1D39} {M}
\__um_setup_active_superscript:nn {"1D3A} {N}
\__um_setup_active_superscript:nn {"1D3C} {O}
\__um_setup_active_superscript:nn {"1D3E} {P}
\__um_setup_active_superscript:nn {"1D3F} {R}
\__um_setup_active_superscript:nn {"1D40} {T}
\__um_setup_active_superscript:nn {"1D41} {U}
\__um_setup_active_superscript:nn {"2C7D} {V}
\__um_setup_active_superscript:nn {"1D42} {W}
\__um_setup_active_superscript:nn {"1D43} {a}
\__um_setup_active_superscript:nn {"1D47} {b}
\__um_setup_active_superscript:nn {"1D9C} {c}
\__um_setup_active_superscript:nn {"1D48} {d}
\__um_setup_active_superscript:nn {"1D49} {e}
\__um_setup_active_superscript:nn {"1DA0} {f}
\__um_setup_active_superscript:nn {"1D4D} {g}
\__um_setup_active_superscript:nn {"02B0} {h}
\__um_setup_active_superscript:nn {"2071} {i}
\__um_setup_active_superscript:nn {"02B2} {j}
\__um_setup_active_superscript:nn {"1D4F} {k}
\__um_setup_active_superscript:nn {"02E1} {l}
\__um_setup_active_superscript:nn {"1D50} {m}
\__um_setup_active_superscript:nn {"207F} {n}
\__um_setup_active_superscript:nn {"1D52} {o}
\__um_setup_active_superscript:nn {"1D56} {p}
\__um_setup_active_superscript:nn {"02B3} {r}
\__um_setup_active_superscript:nn {"02E2} {s}
\__um_setup_active_superscript:nn {"1D57} {t}
\__um_setup_active_superscript:nn {"1D58} {u}
\__um_setup_active_superscript:nn {"1D5B} {v}
\__um_setup_active_superscript:nn {"02B7} {w}
\__um_setup_active_superscript:nn {"02E3} {x}
\__um_setup_active_superscript:nn {"02B8} {y}
\__um_setup_active_superscript:nn {"1DBB} {z}
\__um_setup_active_superscript:nn {"1D5D} {\beta}
\__um_setup_active_superscript:nn {"1D5E} {\gamma}
\__um_setup_active_superscript:nn {"1D5F} {\delta}
\__um_setup_active_superscript:nn {"1D60} {\phi}
\__um_setup_active_superscript:nn {"1D61} {\chi}
\__um_setup_active_superscript:nn {"1DBF} {\theta}
\__um_setup_active_subscript:nn {"2080} {0}
\__um_setup_active_subscript:nn {"2081} {1}
\__um_setup_active_subscript:nn {"2082} {2}
\__um_setup_active_subscript:nn {"2083} {3}
\__um_setup_active_subscript:nn {"2084} {4}
\__um_setup_active_subscript:nn {"2085} {5}
\__um_setup_active_subscript:nn {"2086} {6}
\__um_setup_active_subscript:nn {"2087} {7}
\__um_setup_active_subscript:nn {"2088} {8}
\__um_setup_active_subscript:nn {"2089} {9}
\__um_setup_active_subscript:nn {"208A} {+}
\__um_setup_active_subscript:nn {"208B} {-}
\__um_setup_active_subscript:nn {"208C} {=}
\__um_setup_active_subscript:nn {"208D} {(}
\__um_setup_active_subscript:nn {"208E} {)}
\__um_setup_active_subscript:nn {"2090} {a}
\__um_setup_active_subscript:nn {"2091} {e}
\__um_setup_active_subscript:nn {"2095} {h}
\__um_setup_active_subscript:nn {"1D62} {i}
\__um_setup_active_subscript:nn {"2C7C} {j}
\__um_setup_active_subscript:nn {"2096} {k}
\__um_setup_active_subscript:nn {"2097} {l}
\__um_setup_active_subscript:nn {"2098} {m}
\__um_setup_active_subscript:nn {"2099} {n}
\__um_setup_active_subscript:nn {"2092} {o}
\__um_setup_active_subscript:nn {"209A} {p}
\__um_setup_active_subscript:nn {"1D63} {r}
\__um_setup_active_subscript:nn {"209B} {s}
\__um_setup_active_subscript:nn {"209C} {t}
\__um_setup_active_subscript:nn {"1D64} {u}
\__um_setup_active_subscript:nn {"1D65} {v}
\__um_setup_active_subscript:nn {"2093} {x}
\__um_setup_active_subscript:nn {"1D66} {\beta}
\__um_setup_active_subscript:nn {"1D67} {\gamma}
\__um_setup_active_subscript:nn {"1D68} {\rho}
\__um_setup_active_subscript:nn {"1D69} {\phi}
\__um_setup_active_subscript:nn {"1D6A} {\chi}


\ExplSyntaxOff

\begin{document}

\[ x²³₄₅ + \left( \frac{1}{2} \right) ⁶⁷₈₉ + \int ₁² x \, dx\]

\end{document}

这可能不是实现它的最佳方法，但我想不出更好的方法。

答案3

OpTeX 做得对。

\fontfam[lm]

x²³ and $x²³$.

\bye

在此处输入图片描述

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