在 TeX4ht 中使用 \ifdefined\HCode 时出错，但在 LuaTeX 中可以正常工作

Question 1

编辑：

您还可以使用make4ht过滤器编辑 HTML 文件中的数学内容以获取 MathJax 支持的内容。例如，以下构建文件将dgroup*环境转换为align*，并且还将数学内容更改为合适的形式：

local filter = require "make4ht-filter"

local function process_options(options)
  -- convert [number={foo}] to \tag{foo}
  local number = options:match("number%s*=%s*{?(%w+)")
  if number then
    return "\\tag{" .. number .. "}"
  end
  return ""
end


local function escape_equal(str)
  -- there can be multiple equal characters in the string. we should put the & character
  -- just before the one which is not inside any group
  -- escape nested equal signs
  str = str:gsub("({[^{^}]+)=([^{^}]+})", "%1:EQUAL:%2")
  -- replace remaining =
  str = str:gsub("=", "&=")
  -- return escaped =
  str = str:gsub(":EQUAL:", "=")
  return str
end

local function make_align(dgroup)
  -- change breqn environment contents to align*
  -- change = to &=
  local dgroup = escape_equal(dgroup)
  -- return the fixed text in align* environment
  return "\\begin{align*}" ..  dgroup .. "\\end{align*}"
end

local function process_dgroup(s, env_name)
  return s:gsub("\\begin%s*{" .. env_name .. "}(.-)\\end%s*{" .. env_name .. "}",
  function(dgroup)
    -- remove environemnts
    -- change dmath[...,number={label}] to \tag{label}
    dgroup = dgroup:gsub("\\begin%s*{dmath}%s*(%b[])", process_options)
    -- remove all other environemnts
    dgroup = dgroup:gsub("\\begin%s*{.-}","")
    dgroup = dgroup:gsub("\\end%s*{.-}", "\\\\")
    return make_align(dgroup)
  end)
end

-- process remaining dmath environments
local function process_dmath(s, env_name)
  return s:gsub("\\begin%s*{" .. env_name .. "}(.-)\\end%s*{" .. env_name .. "}",
  function(dmath)
    -- options can be still here
    local dmath = dmath:gsub("^%s*(%b[])", process_options)
    return make_align(dmath)
  end)
end

local process = filter {
  -- find all dgroup* environments and convert them to align*
  function(s)
    local s = process_dgroup(s,"dgroup%*")
    s = process_dgroup(s, "dgroup")
    -- process remaining dmath environments in the document
    s = process_dmath(s, "dmath%*")
    s = process_dmath(s, "dmath")
    return s
  end
}


-- install filter to match HTML files
Make:match("html?$", process)

它生成以下 HTML 代码：

<p class='noindent'>test 1, OK
</p><!-- l. 15 --><p class='indent'>   \begin{align*}  A &amp;= B \\  C &amp;= D \\ \end{align*}
</p><!-- l. 17 --><p class='indent'>   test 2 FAIL
</p><!-- l. 26 --><p class='indent'>   \begin{align*}  A &amp;= B \\ \tag{1} C &amp;= D \\ \end{align*}
</p><!-- l. 29 --><p class='indent'>   test 3 OK
</p><!-- l. 33 --><p class='indent'>   \begin{align*} A &amp;= B \end{align*}
</p><!-- l. 35 --><p class='indent'>   test 4 FAIL
</p><!-- l. 39 --><p class='indent'>   \begin{align*}\tag{1} A &amp;= B \end{align*}
</p><!-- l. 41 --><p class='indent'>   test 5 OK
</p><!-- l. 45 --><p class='indent'>   \begin{align*} A &amp;= B \end{align*}
</p>

MathJax 显示如下：

原始答案：

或者，您可以使用此配置文件向 MathJax 添加对数学环境的支持：

\Preamble{xhtml} 
\Configure{MathJaxConfig}{{ 
    tex: { 
      tags: "ams", 
      \detokenize{% 
      environments: {
        "dgroup*": ["", ""],
        "dmath*": ["", ""],
      } 
  } 
} 
}} 
\VerbMath{dgroup*}
\begin{document} 
\EndPreamble

该\VerbMath{dgroup*}命令确保 TeX4ht 将dgroup*环境的全部内容传递到 HTML 文件。然后您需要配置 MathJax 以支持dgroup*和dmath*环境。这要归功于：

  environments: {
    "dgroup*": ["", ""],
    "dmath*": ["", ""],
  }

我发现您不需要提供任何其他代码，MathJax 只需切换到显示数学模式并打印内容。

你的 TeX 文件可以简化：

\documentclass[12pt]{book}    
\usepackage{amsmath} 
\usepackage{breqn}

\begin{document}    
\begin{dgroup*}
\begin{dmath*}
   A = B
\end{dmath*}     %error is around here           
\end{dgroup*}
\end{document}

结果如下：

Answer

编辑：