我正在寫一份包含問題和答案的文檔。例如
\question{What is 2+3?}{2+3=5}
\question{What is cheese?}{Food made from milk.}
答案會被保存起來，以便在後面的部分中收集，但答案會被打亂以防止偷看。這意味著問題必須包含答案編號的前向引用。例如：
Q2.1 什麼是2+3？（見答案104）
Q2.2 什麼是起司？（見答案57）
我有這個幾乎在職的。
該\question命令將所有答案寫入臨時文件，稍後的\printtheanswers命令將其發送到外部程序
A。打亂答案，
b.為答案部分生成 Latex，並且
C。產生一個輔助文件，其中qa.aux定義等來保存前向引用。\answernumber1\answernumber2
這是一個兩遍編譯。qa.aux如果檔案存在，則在開始時載入該檔案。該\question命令必須\answernumberN為每個不存在的命令進行定義，以擴展為佔位符。
目前，\question是部分定義的——它總是定義\answernumberN為佔位符：
\newcommand{\question}[2]{
\stepcounter{questionnumber}
\stepcounter{questionnumberinchapter}
% Define the placeholder for \answernumberN
\expandafter\edef\expandafter\answernumber\roman{questionnumber}{PLACEHOLDER:\arabic{questionnumber}}
% FOR DEBUGGING
DEFINING \texttt{\textbackslash answernumber\roman{questionnumber} as \{PLACEHOLDER:\arabic{questionnumber}\}}
% Write "x.y #2" to \qainpfilename
\immediate\write\qafile{\arabic{chapter}.\arabic{questionnumberinchapter} \unexpanded{#2}}
% Print the qustion to the document.
Q\arabic{chapter}.\arabic{questionnumberinchapter} #1 \emph{(See answer \expandafter\answernumber\roman{questionnumber}.)}
}
這是有興趣的線：
\expandafter\edef\expandafter\answernumber\roman{questionnumber}{PLACEHOLDER:\arabic{questionnumber}}
問題是this 總是定義\answernumberN，無論它是否在輔助檔案中定義。
這是一個 MWE，儘管沒有外部程式您實際上無法編譯它。
\documentclass[a4paper,10pt,openany]{scrbook}
\usepackage{verbatim}
% Define \bashline command
% Taken from https://gist.github.com/w495/7328b76e76aee49657e0bd7a3b46c870
\makeatletter
\newcommand{\bashline@file@name}[1]{%
/tmp/${USER}-${HOSTNAME}-\jobname-#1.tex%
}
\newread\bashline@file
\newcommand{\bashline@command@one}[2][tmp]{%
\immediate\write18{#2 > \bashline@file@name{#1}}
\openin\bashline@file=\bashline@file@name{#1}
% The group localizes the change to \endlinechar
\bgroup
\endlinechar=-1
\read\bashline@file to \localline
% Since everything in the group is local,
% we have to explicitly make the assignment global
\global\let\bashline@result\localline
\egroup
\closein\bashline@file
% Clean up after ourselves
\immediate\write18{rm \bashline@file@name{#1}}
\bashline@result
}
\newcommand{\bashline@command@many}[2][tmp]{%
\immediate\write18{#2 > \bashline@file@name{#1}}
\openin\bashline@file=\bashline@file@name{#1}
% The group localizes the change to \endlinechar
\newcount\linecnt
\bgroup
\endlinechar=-1
\loop\unless\ifeof\bashline@file
\read\bashline@file to \localline%
\localline
\newline
\repeat
\egroup
\closein\bashline@file
% Clean up after ourselves
\immediate\write18{rm \bashline@file@name{#1}}
}
\newcommand{\bashline}[2][tmp]{%
\bashline@command@one[#1]{#2}%
}
\newcommand{\bashlines}[2][tmp]{%
\bashline@command@many[#1]{#2}%
}
\makeatother
% Question-answer stuff.
\def\qainpfilename{qa.inp}
\def\qaauxfilename{qa.aux}
\def\qatexfilename{qa.tex}
\newwrite\qafile
\immediate\openout\qafile=\qainpfilename
\newcounter{questionnumber}
\newcounter{questionnumberinchapter}[chapter]
\newcommand{\question}[2]{
\stepcounter{questionnumber}
\stepcounter{questionnumberinchapter}
% Define the placeholder for \answernumberN
\expandafter\edef\expandafter\answernumber\roman{questionnumber}{PLACEHOLDER:\arabic{questionnumber}}
DEFINING \texttt{\textbackslash answernumber\roman{questionnumber} as \{PLACEHOLDER:\arabic{questionnumber}\}}
% Write "x.y #2" to \qainpfilename
\immediate\write\qafile{\arabic{chapter}.\arabic{questionnumberinchapter} \unexpanded{#2}}
% Print the qustion to the document.
Q\arabic{chapter}.\arabic{questionnumberinchapter} #1 \emph{(See answer \expandafter\answernumber\roman{questionnumber}.)}
}
\newcommand{\printtheanswers}{
\immediate\closeout\qafile
\bashline{bash bin/generate-answers.sh '\qainpfilename' '\qatexfilename' '\qaauxfilename'}
\input{\qatexfilename}
}
% Demonstrate that this will not be expanded until after qa.tex has been
% generated loaded into the document.
\def\examplething{this is expanded later}
\begin{document}
TEST
\IfFileExists{\qaauxfilename}{\input{\qaauxfilename}}{AUX DOES NOT EXIST}
\chapter{Maths}
\question{What is $1+2$?}{$1+2=3$ \examplething}
\question{What is $2\times 3$?}{$2\times 3=6$}
\chapter{Science}
\question{Name the six quarks.}{Up down, charm, strange, truth, and beauty.}
\question{How many planets orbit the Sun?}{Eight. Deal with it.}
\chapter{Answers}
\printtheanswers
\end{document}
qa.aux為此文件產生的文件是
\def\answernumberi{3}% (Q1.1): $1+2=3$ \examplething
\def\answernumberii{1}% (Q1.2): $2\times 3=6$
\def\answernumberiii{4}% (Q2.1): Up down, charm, strange, truth, and beauty.
\def\answernumberiv{2}% (Q2.2): Eight. Deal with it.
我知道您可以使用\providecommand各種 if-then 結構，但是當命令名稱使用\expandafter\answernumber\roman{questionnumber}.如何有條件地定義一個命令，其名稱是由這樣的數字建構的？
答案1
感謝cfr，我現在使用\label和\ref
該\question命令現在包括
Q\arabic{chapter}.\arabic{questionnumberinchapter} #1 \emph{(See answer \expandafter\ref{\expandafter qanswer\arabic{questionnumber}}.)}
該\printtheanswers指令產生如下 tex：
\item\label{qanswer123} (text of answer to the 123rd question)