插入 \forall 后

Question

\documentclass{article}
\usepackage[ruled,vlined]{algorithm2e}
\usepackage{amsmath}

\begin{document}

\begin{algorithm}

\SetKwInOut{Input}{input}
\SetKwInOut{Output}{output}

\Input{A set of relations $R(x,y)$ participating in query, JoinKey}
\Output{ key , value pairs}

\forall{\text{$joinKey$}}{
\eIf{$joinKey$ is missing from $R$}{
$Key \leftarrow {\tt JoiningElement}$ 
$Value \leftarrow {\tt 1stTableName + OtherElements}$ \tcc*[r]{first round=$R,a$ / second round=$R',a,b$}
}{
$Key \leftarrow {\tt JoiningElement}$\;
$Value \leftarrow {\tt 2ndTableName + OtherElements}$\; 
}
}
\caption{ Phase 1 \label{IR}}
\end{algorithm}

为什么我会收到此错误

Missing $ inserted.
<inserted text> 
                $
l.15 \forall
            {\text{$joinKey$}}{ 

Answer 1

\forall是一个数学符号。algorithm2e定义\ForAll：

\documentclass{article}

\usepackage[ruled,vlined]{algorithm2e}

\SetKwInOut{Input}{input}
\SetKwInOut{Output}{output}
\newcommand{\var}{\texttt}% Formatting of variables

\begin{document}

\begin{algorithm}

  \Input{A set of relations $R(x,y)$ participating in query, \var{JoinKey}}
  \Output{key, value pairs}

  \ForAll{\var{joinKey}}{
    \eIf{\var{joinKey} is missing from $R$}{
      $\var{Key} \leftarrow \var{JoiningElement}$
      $\var{Value} \leftarrow \var{1stTableName} + \var{OtherElements}$ \tcc*[r]{first round = $R,a$ / second round = $R',a,b$}
    }{
      $\var{Key} \leftarrow \var{JoiningElement}$
      $\var{Value} \leftarrow \var{2ndTableName} + \var{OtherElements}$
    }
  }
  \caption{Phase 1}
\end{algorithm}

\end{document}