显示数学模式和“中心”环境

Question 1

你可以将示例简化为

\documentclass{article}

\begin{document}

\mbox{$ \times $}

\mbox{$$ \times $$}

\mbox{\begin{center} x \end{center}}

\end{document}

你没有得到任何错误$但$$产生了

! Missing $ inserted.
<inserted text> 
                $
l.7 \mbox{$$ \times $$}
                       
?

因为在 hbox 中$$类似于 $ $ 并创建一个空的数学列表所以\times它不处于数学模式，它位于两个空的数学列表之间的文本中。

并center产生

! LaTeX Error: Something's wrong--perhaps a missing \item.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...                                              
                                                  
l.9 \mbox{\begin{center} x \end{center}}
                                        
?

因为你不能在水平框中构建垂直显示结构。

所以你肯定不想

%% Define the command to hide the text body of the environment.
\newlength{\trashlength}%
\def\hide@text#1{%
    \settowidth{\trashlength}{#1}
}

它的作用类似于错误，\mbox并且是错误的原因，您可能也不想要\StrDel。您没有在任何地方说明您希望此代码执行什么操作，我猜不到，因此这个答案仅限于解释为什么会出现错误，我无法建议替代代码。

Answer

你可以将示例简化为

\documentclass{article}

\begin{document}

\mbox{$ \times $}

\mbox{$$ \times $$}

\mbox{\begin{center} x \end{center}}

\end{document}

你没有得到任何错误$但$$产生了

! Missing $ inserted.
<inserted text> 
                $
l.7 \mbox{$$ \times $$}
                       
?

因为在 hbox 中$$类似于 $ $ 并创建一个空的数学列表所以\times它不处于数学模式，它位于两个空的数学列表之间的文本中。

并center产生

! LaTeX Error: Something's wrong--perhaps a missing \item.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...                                              
                                                  
l.9 \mbox{\begin{center} x \end{center}}
                                        
?

因为你不能在水平框中构建垂直显示结构。

所以你肯定不想

%% Define the command to hide the text body of the environment.
\newlength{\trashlength}%
\def\hide@text#1{%
    \settowidth{\trashlength}{#1}
}

它的作用类似于错误，\mbox并且是错误的原因，您可能也不想要\StrDel。您没有在任何地方说明您希望此代码执行什么操作，我猜不到，因此这个答案仅限于解释为什么会出现错误，我无法建议替代代码。

Question 2

正如我在评论中指出的那样，在这种情况下避免使用\[..\](和)，而应使用。使用而不是环境。因此，将给出一个居中方程（如果需要限制居中范围，可以使用括号）。$$...$$ $...$ \centeringcenter\centering $...${\centering $...$\par}

\displaystyle如果您希望进一步模拟所提供的显示样式外观，您可能会或可能不会希望在等式开头添加材料\[...\]。

\documentclass[12pt,a4paper]{article}
\usepackage[tikz]{moodle}
\usepackage{ifthen}
\usepackage{etoolbox}
\usepackage{environ}
\usepackage{xstring}
\usepackage{amsmath,amssymb,yhmath,mathrsfs,fontawesome}
\usepackage{fancyhdr,enumerate,tkz-euclide,tikz-3dplot,tikz,tkz-tab}
\moodleregisternewcommands

\makeatletter
\newcounter{c@ex}%
\setcounter{c@ex}{0}
\newcounter{ans@wer}%
\newcounter{correct@answer}%
\newcommand{\True}{}%
\newcommand\exname{MC}
%% Define the command to hide the text body of the environment.
\newlength{\trashlength}%
\def\hide@text#1{%
    \settowidth{\trashlength}{#1}
}
%% Define the command to find the correct answer.
\def\begin@ans{\@ifnextchar\True
{\setcounter{correct@answer}{\theans@wer}}{\stepcounter{ans@wer}}%
}
\environbodyname\@body
\htmlregister\@body
\htmlregister\final@result
\htmlregister\ans@one
\htmlregister\ans@two
\htmlregister\ans@three
\htmlregister\ans@four
\htmlregister\feed@back
\htmlregister\envbody
\newcommand{\choice}[4]{
    \gdef\ans@one{#1}
    \gdef\ans@two{#2}
    \gdef\ans@three{#3}
    \gdef\ans@four{#4}
    \gdef\del@choice{\choice
    {#1}
    {#2}
    {#3}
    {#4}
    }%
}%
\newcommand{\loigiai}[1]{
    \gdef\feed@back{#1}
    \gdef\del@feedback{\loigiai{#1}}
}%
\NewEnviron{ex}{%
}%
\AtEndEnvironment{ex}{%
    \stepcounter{c@ex}
    \hide@text{\@body}
%% Delete the macro \choice and \loigiai in the body of environment
    \hide@text{
        \global\let\@result\@body
        \expandarg
        \StrDel{\@result}{\del@choice}[\re@sult]
        \StrDel{\re@sult}{\del@feedback}[\re@@sult]
        \global\let\final@result\re@@sult
    }
%   \let\envbody\noexpand{\funal@result}
%% Finding the correct answer
\setcounter{ans@wer}{1}
\hide@text{\expandafter\begin@ans\ans@one}
\hide@text{\expandafter\begin@ans\ans@two}
\hide@text{\expandafter\begin@ans\ans@three}
\hide@text{\expandafter\begin@ans\ans@four}
%% Write the data in `milti' environment
\def\ex@name{\exname\thec@ex}
\ifnum\the\value{correct@answer}=1%
    \begin{multi}[numbering=ABCD,penalty=0,feedback={\feed@back}]{\ex@name}         
            \final@result
            \item* \ans@one%
            \item \ans@two%
            \item \ans@three%
            \item \ans@four%
    \end{multi}
\else
\ifnum\the\value{correct@answer}=2%
    \begin{multi}[numbering=ABCD,penalty=0,feedback={\feed@back}]{\exname\thec@ex}
            \final@result
            \item \ans@one%
            \item* \ans@two%
            \item \ans@three%
            \item \ans@four%
    \end{multi}
\else
\ifnum\the\value{correct@answer}=3
    \begin{multi}[numbering=ABCD,penalty=0,feedback={\feed@back}]{\exname\thec@ex}
            \final@result
            \item \ans@one%
            \item \ans@two%
            \item* \ans@three%
            \item \ans@four%
    \end{multi}
\else
\ifnum\the\value{correct@answer}=4
    \begin{multi}[numbering=ABCD,penalty=0,feedback={\feed@back}]{\exname\thec@ex}
            \final@result
            \item \ans@one%
            \item \ans@two%
            \item \ans@three%
            \item* \ans@four%   
    \end{multi}
\else
\relax
\fi
\fi
\fi
\fi
}%
\makeatother

\begin{document}
\begin{quiz}{My first test}
\begin{ex}
\centering This is my question. $\dfrac{a}{b}$

 $\dfrac{c}{d}$
\choice
{\True Answer one}
{Answer two}
{Answer three}
{Answer four}
\loigiai{This is a detail answer.}
\end{ex}
\end{quiz}
\end{document}

Answer

正如我在评论中指出的那样，在这种情况下避免使用\[..\](和)，而应使用。使用而不是环境。因此，将给出一个居中方程（如果需要限制居中范围，可以使用括号）。$$...$$ $...$ \centeringcenter\centering $...${\centering $...$\par}

\displaystyle如果您希望进一步模拟所提供的显示样式外观，您可能会或可能不会希望在等式开头添加材料\[...\]。

\documentclass[12pt,a4paper]{article}
\usepackage[tikz]{moodle}
\usepackage{ifthen}
\usepackage{etoolbox}
\usepackage{environ}
\usepackage{xstring}
\usepackage{amsmath,amssymb,yhmath,mathrsfs,fontawesome}
\usepackage{fancyhdr,enumerate,tkz-euclide,tikz-3dplot,tikz,tkz-tab}
\moodleregisternewcommands

\makeatletter
\newcounter{c@ex}%
\setcounter{c@ex}{0}
\newcounter{ans@wer}%
\newcounter{correct@answer}%
\newcommand{\True}{}%
\newcommand\exname{MC}
%% Define the command to hide the text body of the environment.
\newlength{\trashlength}%
\def\hide@text#1{%
    \settowidth{\trashlength}{#1}
}
%% Define the command to find the correct answer.
\def\begin@ans{\@ifnextchar\True
{\setcounter{correct@answer}{\theans@wer}}{\stepcounter{ans@wer}}%
}
\environbodyname\@body
\htmlregister\@body
\htmlregister\final@result
\htmlregister\ans@one
\htmlregister\ans@two
\htmlregister\ans@three
\htmlregister\ans@four
\htmlregister\feed@back
\htmlregister\envbody
\newcommand{\choice}[4]{
    \gdef\ans@one{#1}
    \gdef\ans@two{#2}
    \gdef\ans@three{#3}
    \gdef\ans@four{#4}
    \gdef\del@choice{\choice
    {#1}
    {#2}
    {#3}
    {#4}
    }%
}%
\newcommand{\loigiai}[1]{
    \gdef\feed@back{#1}
    \gdef\del@feedback{\loigiai{#1}}
}%
\NewEnviron{ex}{%
}%
\AtEndEnvironment{ex}{%
    \stepcounter{c@ex}
    \hide@text{\@body}
%% Delete the macro \choice and \loigiai in the body of environment
    \hide@text{
        \global\let\@result\@body
        \expandarg
        \StrDel{\@result}{\del@choice}[\re@sult]
        \StrDel{\re@sult}{\del@feedback}[\re@@sult]
        \global\let\final@result\re@@sult
    }
%   \let\envbody\noexpand{\funal@result}
%% Finding the correct answer
\setcounter{ans@wer}{1}
\hide@text{\expandafter\begin@ans\ans@one}
\hide@text{\expandafter\begin@ans\ans@two}
\hide@text{\expandafter\begin@ans\ans@three}
\hide@text{\expandafter\begin@ans\ans@four}
%% Write the data in `milti' environment
\def\ex@name{\exname\thec@ex}
\ifnum\the\value{correct@answer}=1%
    \begin{multi}[numbering=ABCD,penalty=0,feedback={\feed@back}]{\ex@name}         
            \final@result
            \item* \ans@one%
            \item \ans@two%
            \item \ans@three%
            \item \ans@four%
    \end{multi}
\else
\ifnum\the\value{correct@answer}=2%
    \begin{multi}[numbering=ABCD,penalty=0,feedback={\feed@back}]{\exname\thec@ex}
            \final@result
            \item \ans@one%
            \item* \ans@two%
            \item \ans@three%
            \item \ans@four%
    \end{multi}
\else
\ifnum\the\value{correct@answer}=3
    \begin{multi}[numbering=ABCD,penalty=0,feedback={\feed@back}]{\exname\thec@ex}
            \final@result
            \item \ans@one%
            \item \ans@two%
            \item* \ans@three%
            \item \ans@four%
    \end{multi}
\else
\ifnum\the\value{correct@answer}=4
    \begin{multi}[numbering=ABCD,penalty=0,feedback={\feed@back}]{\exname\thec@ex}
            \final@result
            \item \ans@one%
            \item \ans@two%
            \item \ans@three%
            \item* \ans@four%   
    \end{multi}
\else
\relax
\fi
\fi
\fi
\fi
}%
\makeatother

\begin{document}
\begin{quiz}{My first test}
\begin{ex}
\centering This is my question. $\dfrac{a}{b}$

 $\dfrac{c}{d}$
\choice
{\True Answer one}
{Answer two}
{Answer three}
{Answer four}
\loigiai{This is a detail answer.}
\end{ex}
\end{quiz}
\end{document}

Question 3

实际上，您需要做的就是将输入结构转换为moodle期望的输入结构。这里我假设你的输入数据总是具有以下结构

\begin{ex}
  Question text
  \choice{...}{...}{...}{...}
  \loigiai{...}
\end{ex}

（特别是，\choice总是出现在“问题文本”之后，并且\loigiai总是出现在最后，并且每个问题都有一个\loigiai命令（反馈不是可选的）。）

在这种情况下，如果你ex使用进行定义\NewEnviron，则可以\BODY用以下形式的分隔宏进行解析

\long\def\@transformBody#1\choice#2#3#4#5\loigiai#6{...}

其中#1成为问题文本，#2...#5是选项，#6是反馈。人们可以尝试执行适当的转换并将内容塞入\begin{multi}...\end{multi}，但由于后者也是从构建的\NewEnviron，我们也可以省去中间人，只需复制的定义并multi放入适当的内容即可。

然而还有最后一个问题：你原来的格式用标记了正确答案，\Truemoodle 使用*。在这里我做了另一个假设：你总是把\True答案放在开头。基本上，我希望能够扩展\True为*而不影响其余的选择文本；对于列表中的第一个标记来说，这很容易做到。

备注：可能还有其他我没考虑到的因素，但至少对于基本测试用例，以下方法有效。以下方法包含一些解释

\documentclass{article}
\usepackage[tikz]{moodle}
\usepackage{amsmath}
\usepackage{ifthen}
\usepackage{etoolbox}
\usepackage{environ}

\newcommand\True{*} %% Makes \True expand to *

\makeatletter
%%%%
\long\def\@transformBody#1\choice#2#3#4#5\loigiai#6{%
        %% The purpose of the next four lines are to expand the first token
        %% of the answer choices, so that \True -> *
        \ExpandArgs{Nf}\def\my@choice@A{#2}
        \ExpandArgs{Nf}\def\my@choice@B{#3}
        \ExpandArgs{Nf}\def\my@choice@C{#4}
        \ExpandArgs{Nf}\def\my@choice@D{#5}
        %% The next command creates the processed body text to pass on for
        %% processing by Moodle's internal commands. The complicated 
        %% string of \expandafter's are all because of the \True -> * replacement
        \long\edef\ex@NewBody{\unexpanded{#1}
                \noexpand\item\expandafter\unexpanded\expandafter{\my@choice@A}
                \noexpand\item\expandafter\unexpanded\expandafter{\my@choice@B}
                \noexpand\item\expandafter\unexpanded\expandafter{\my@choice@C}
                \noexpand\item\expandafter\unexpanded\expandafter{\my@choice@D}}%
        %% This stashes the feedback somewhere
        \def\ex@feedback{#6}%
}
\newcounter{mymulti}
\NewEnviron{ex}{%
        \refstepcounter{mymulti}
        \expandafter\@transformBody\BODY   %Process the \BODY
    \bgroup
      \setkeys{moodle}{numbering=ABCD,penalty=0,feedback={\ex@feedback},questionname={MC\themymulti}}% Sets most of the Moodle parameters for the MC question
      \global\advance\moodle@totalmarks by \csname moodle@default grade\endcsname pt
      \expandafter\gatheritems\xa{\ex@NewBody}% Feed the Moodle Processor the transformed body text
      %% everything below is copied straight from the definition of the 
      %% multi environment in moodle.sty
      \let\moodle@questionheader=\gatheredheader
      %First, the LaTeX processing
      \item \moodle@begin@samepage \textbf{\moodle@questionname}
      \ifmoodle@handout
        \moodle@makelatextag@qtype{multi}
      \else
        \moodle@latex@writetags
        \par
        \noindent
        \moodle@makelatextag@qtype{multi}%
        \moodle@makelatextag@value{default grade}{marked out of}
        \moodle@makelatextag@value{penalty}{penalty}%
      \fi
      \moodle@makelatextag@multi\par
      \noindent
      \moodle@questionheader
      \edef\moodle@generalfeedback{\expandonce\moodle@feedback}
      \csname moodle@multi@latexprocessing\endcsname
      \moodle@end@samepage
      %Now, writing information to XML
      \@moodle@ifgeneratexml{%
        \xa\questiontext\xa{\moodle@questionheader}% Save the question text.
        \csname writemultiquestion\endcsname
        \bgroup
          \gdef\moodle@answers@xml{}%
          \setkeys{moodle}{feedback={}}%
          \xa\loopthroughitemswithcommand\xa{\csname savemultianswer\endcsname}%
          \passvalueaftergroup{\moodle@answers@xml}%
        \egroup
        \moodle@writeanswers%
        \moodle@writetags%
        \writetomoodle{</question>}%
      }{}%
    \egroup
}%

%%%%






\makeatother

\moodleregisternewcommands


\begin{document}
\begin{quiz}{A}
\begin{ex}
This is my question. $\dfrac{a}{b}$

\choice
{\True Answer one}
{$15$ Answer two}
{Answer three}
{Answer four}
\loigiai{This is a detail answer.}
\end{ex}
\end{quiz}
\end{document}

Answer