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根据难度筛选练习

tag-icon • tag-icon key-value exercises
根据难度筛选练习

这在某种程度上是一个后续问题这个问题。我在写答案的时候遇到了这个问题，但我以为我以后可以轻松解决这个问题，结果却错了。真可惜。

问题是，虽然过滤器对于诸如的键可以正常工作type，但对于键却不行difficulty。

以下是 MWE：

\documentclass{article}

\usepackage{exercise}

\begin{document}

Here is a short exercise :

\ExerciseSelect[type={short}]

\begin{Exercise}[type={short}]
  Prove that $1+1=2$. 
\end{Exercise}

\begin{Exercise}[type={long}]
  Prove that $P \neq NP$.
\end{Exercise}

\ExerciseStopSelect

\vspace{1cm}\hrule\vspace{1cm}

Now here is a hard exercise :
\ExerciseSelect[difficulty={2}]

\begin{Exercise}[difficulty=0]
  Prove that $1+1=2$. 
\end{Exercise}

\begin{Exercise}[difficulty=2]
  Prove that $P \neq NP$.
\end{Exercise}

\ExerciseStopSelect

Or an easy one :

\ExerciseSelect[difficulty={0}]

\begin{Exercise}[difficulty={0}]
  Prove that $1+1=2$. 
\end{Exercise}

\begin{Exercise}[difficulty={2}]
  Prove that $P \neq NP$.
\end{Exercise}

\ExerciseStopSelect


\end{document}

其输出如下：

输出

正如您所见，过滤器没有选择任何内容difficulty。

答案1

解决方案比我最初想象的要复杂一些。该软件包exercise过于依赖计数器来确定难度级别，因此我的第一个方法没有用。我认为，在测试难度标志时，是其对应的计数器导致标志无法升起。

我在这里所做的是保存代码中exercise我认为不需要重写但确实需要扩充的部分。我还创建了一个新的标志调用howdifficult。它的设置方式与相同，difficult我相信具有相同的预期效果。（我还没有测试所有可能的情况，但这需要我比以前更彻底地阅读手册。）

下面的代码似乎有效。该difficulty键触发了几个标志。我认为此代码触发了所有必要的标志。但就目前而言，这确实提供了一个无错误的补丁。

\makeatletter
%% Adding new key to the "Exercise" environment
%% save old initialization code in a temporary command and then redefine.
\let\@tmp@InitExe\@InitExe
\def\@InitExe{\@tmp@InitExe%
    \gdef\ExerciseHowDifficult{}%
    \global\@ExeHowDifficultfalse%
}
%% For "Exercise" environment flags, set key-value="howdifficult" and
%% corresponding flags to true.  Also, set the counter for
%% key-value='difficult'. These additional settings for 'difficulty' may
%% not be necessary; I've put it here just to be on the safe side.
\newif\if@ExeHowDifficult \@ExeHowDifficultfalse
\define@key{PPExercise}{howdifficult}%
{\global\@ExeHowDifficulttrue\gdef\ExerciseHowDifficult{#1}%
    \global\@ExeDifficultytrue%
    \global\ExerciseDifficulty=\number#1}
%% set the Header       for key-value="howdifficult" 
%% to be the header used by key-value="difficulty"
\let\@tmp@getExerciseInfo\@getExerciseInfo
\def\@getExerciseInfo{\@tmp@getExerciseInfo%
    \if@ExeHowDifficult\else\def\ExerciseHeaderDifficulty{}\fi%
}
%% Adding new key to "Exercise Selection" routine to guarantee shipout
%% routine is properly carried out.
%% save old initialization code in a temporary command and then redefine.
\let\@tmp@selectExercise\@selectExercise
\def\@selectExercise{\@tmp@selectExercise%
    \if@ExeSelectHowDifficult
    \@for\@howdifficult:=\ExerciseSelectHowDifficult\do
    { \ifthenelse{\equal{\@howdifficult}{\ExerciseHowDifficult}}{
            \global\@@ShipThisExercisetrue
        }{}
    }
    \if@@ShipThisExercise\else\@ShipThisExercisefalse\fi
    \global\@@ShipThisExercisefalse
    \fi
}
%% Set appropriate difficulty flags for exercise selection.
\newif\if@ExeSelectHowDifficult          \@ExeSelectHowDifficultfalse
\define@key{PPExerciseSelect}{howdifficult}%
{\global\@ExeSelectHowDifficulttrue\gdef\ExerciseSelectHowDifficult{#1}}
%----------------------------------------------------------------------
%% It's not clear to me that the following code is at all necessary.  I
%% put it here so that the user of the package can completely dispense with
%% all uses of the key-value="difficulty".
%----------------------------------------------------------------------
%% translate infor from key-value="howdifficult" to "\QuestionDifficulty"
\define@key{PPQuestion}{howdifficult}{%
\global\@QuestionDifficultytrue\global\QuestionDifficulty=\number#1}
%% translate infor from key-value="howdifficult" to "\subQuestionDifficulty"
\define@key{PPsubQuestion}{howdifficult}{%
\global\@subQuestionDifficultytrue\global\subQuestionDifficulty=\number#1}
%% translate infor from key-value="howdifficult" to "\subsubQuestionDifficulty"
\define@key{PPsubsubQuestion}{howdifficult}{%
\global\@subsubQuestionDifficultytrue\global\subsubQuestionDifficulty=\number#1}
%% translate infor from key-value="howdifficult" to "\ExePartDifficulty"
\define@key{PPExePart}{howdifficult}{\global\@ExePartDifficultytrue%
\global\ExePartDifficulty=\number#1}
\makeatother

我应该指出，同时使用键值difficulty和可能会导致不确定的结果。因此，我添加了代码，虽然不是完全必要的，但允许包的用户在所有可能需要的情况下howdifficult忘记密钥difficulty和用户。howdifficult

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