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content/blog/hiding-answers-lecture-slides-latex-beamer.md

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+---
+title: "Hiding Answers in Lecture Slides using Latex Beamer"
+date: 2023-10-09T11:40:36-04:00
+draft: false
+tags: ["LaTex"]
+math: false
+medium_enabled: false
+---
+
+Asking questions is a great way to try to solicitate engagement from students. However, it can feel at odds with trying to provide a fully comprehensive slide deck at times. Similar to having notes [hidden for yourself](/blog/notes-beamer-latex/), we should also have a way to hide answers for the students of the present but not the students of the future.
+
+LaTex beamer has the `\invisible` command which holds the space for the text but doesn't display it. We can create a new command with an if statement stating whether or not we want to use `\invisible`.
+
+For this, I called the variable `showanswer`, but you can call it whatever you like. Put the following code in the preamble of your beamer document.
+
+```latex
+\newif\ifshowanswer
+%\showanswertrue % Uncomment when you want to show the answer
+\newcommand{\HideAns}[1]{\unless\ifshowanswer \invisible{#1} \else #1 \fi}
+```
+
+To write `if not` in LaTex, we need to use `\unless\if`.
+
+Now let's see this in action. Here is a slide I gave in a recent lecture about Unification:
+
+```latex
+\begin{frame}{Examples}
+	\begin{enumerate}
+		\item $f(x, y) \eq f(g(x), b)$
+		\begin{itemize}
+			\item Answer: \HideAns{None - Occurs Check}
+		\end{itemize}
+		
+		\item $f(x, a) \eq f(a, b)$
+		\begin{itemize}
+			\item Answer: \HideAns{None - Function Clash}
+		\end{itemize}
+		
+		\item $g(x) \eq g(y)$
+		\begin{itemize}
+			\item Answer: \HideAns{$x \mapsto y$}
+		\end{itemize}
+	\end{enumerate}
+\end{frame}
+```
+
+The left shows the hidden version, and the right shows the version I can distribute afterwards.
+
+![Screenshot showing example with and without hidden answers](/files/images/blog/20231009120041.png)
+
+Minimal Working Example:
+```latex
+\documentclass{beamer}
+\usetheme{Copenhagen}
+\usepackage[utf8]{inputenc}
+
+\newcommand{\eq}{\stackrel{?}{=}}
+
+\newif\ifshowanswer
+% \showanswertrue % Uncomment when you want to show the answer
+\newcommand{\HideAns}[1]{\unless\ifshowanswer \invisible{#1} \else #1 \fi}
+
+\begin{document}
+\begin{frame}{Examples}
+	\begin{enumerate}
+		\item $f(x, y) \eq f(g(x), b)$
+		\begin{itemize}
+			\item Answer: \HideAns{None - Occurs Check}
+		\end{itemize}
+		\item $f(x, a) \eq f(a, b)$
+		\begin{itemize}
+			\item Answer: \HideAns{None - Function Clash}
+		\end{itemize}
+		\item $g(x) \eq g(y)$
+		\begin{itemize}
+			\item Answer: \HideAns{$x \mapsto y$}
+		\end{itemize}
+	\end{enumerate}
+\end{frame}
+\end{document}
+
+```
+
+
+