Change small tables of arithmetic operators from 'longtable' to 'tabu…

…lar'

This removes the last uses of 'longtable' in this chapter.

chapters/operatorsandexpressions.tex

@@ -140,15 +140,20 @@ \subsection{Example: Guarding Expressions Against Incorrect Evaluation}\label{ex
 
 \section{Arithmetic Operators}\label{arithmetic-operators}
 
-Modelica supports five binary arithmetic operators that operate on any
-numerical type:
-\begin{longtable}[c]{ll}
+Modelica supports five binary arithmetic operators that operate on any numerical type:
+\begin{center}
+\begin{tabular}{c|l}
+\tablehead{Operator} & \tablehead{Description} \\
+\hline
+\hline
 \lstinline!^! & Exponentiation\\
 \lstinline!*! & Multiplication\\
 \lstinline!/! & Division\\
 \lstinline!+! & Addition\\
 \lstinline!-! & Subtraction\\
-\end{longtable}
+\hline
+\end{tabular}
+\end{center}
 
 Some of these operators can also be applied to a combination of a scalar
 type and an array type, see \cref{scalar-vector-matrix-and-array-operator-functions}.
@@ -174,29 +179,38 @@ \section{Arithmetic Operators}\label{arithmetic-operators}
 
 \section{Equality, Relational, and Logical Operators}\label{equality-relational-and-logical-operators}
 
-Modelica supports the standard set of relational and logical operators,
-all of which produce the standard boolean values \lstinline!true! or \lstinline!false!.
-
-
-\begin{longtable}[]{ll}
-\lstinline!>! & greater than\\
-\lstinline!>=! & greater than or equal\\
-\lstinline!<! & less than\\
-\lstinline!<=! & less than or equal to\\
-\lstinline!==! & equality within expressions\\
+Modelica supports the standard set of relational and logical operators, all of which produce the standard boolean values \lstinline!true! or \lstinline!false!:
+\begin{center}
+\begin{tabular}{c|l}
+\tablehead{Operator} & \tablehead{Description} \\
+\hline
+\hline
+\lstinline!>! & Greater than\\
+\lstinline!>=! & Greater than or equal\\
+\lstinline!<! & Less than\\
+\lstinline!<=! & Less than or equal to\\
+\lstinline!==! & Equality within expressions\\
 \lstinline!<>! & Inequality\\
-\end{longtable}
+\hline
+\end{tabular}
+\end{center}
 
 A single equals sign \lstinline!=! is never used in relational expressions, only in
 equations (\cref{equations}, \cref{equality-and-assignment}) and in function calls using named
 parameter passing (\cref{positional-or-named-input-arguments-of-functions}).
 
 The following logical operators are defined:
-\begin{longtable}[]{ll}
-\lstinline!not! & negation, unary operator\\
-\lstinline!and! & logical and\\
-\lstinline!or! & logical or\\
-\end{longtable}
+\begin{center}
+\begin{tabular}{c|l}
+\tablehead{Operator} & \tablehead{Description} \\
+\hline
+\hline
+\lstinline!not! & Logical negation (unary operator)\\
+\lstinline!and! & Logical \emph{and} (conjunction)\\
+\lstinline!or! & Logical \emph{or} (disjunction)\\
+\hline
+\end{tabular}
+\end{center}
 
 The grammar rules define the syntax of the relational and logical
 operators.