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+\section{Error handling}
+
+All syntactic and semantic errors throw exceptions. In particular,
+the methods used to match tokens in the parser base class (match
+etc) throw §EdpgMismatchedToken§. The methods in the lexer base
+class used to match characters (match etc) throw exceptions
+similarly.
+
+\subsection{DPG exception hierarchy}
+
+DPG-generated parsers throw exceptions to signal recognition
+errors or other stream problems. All exceptions derive from
+EdpgException. The hierarchy is as follows:
+
+\begin{verbatim}
+   EdpgException
+      EdpgMismatchedChar
+      EdpgMismatchedToken
+      EdpgSemantic
+\end{verbatim}
+
+\subsection{EdpgException}
+The §EdpgException§ is the base class for all DPG exceptions. It
+defines the following read-only properties:
+\begin{alltt}
+   FileName : string;
+   Line     : integer;
+   Column   : integer;
+\end{alltt}
+These properties contain information about the location where the exception
+occurred.
+
+\subsection{EdpgMismatchedChar}
+The §EdpgMismatchedChar§ exception is thrown by the lexer when it
+is looking for a character, but finds a different one on the input
+stream than expected. It defines the following properties in
+addition to those of §EdpgException§.
+\begin{alltt}
+   FoundChar    : char;
+   FoundString  : string;
+   CharSet      : TdpgCharSet;
+   Str          : string;
+   Inverted     : boolean;
+\end{alltt}
+The §FoundChar§ and §FoundString§ properties contain the character
+or string that was found on the input stream. The §CharSet§ and
+§Str§ properties contain the values which the lexer expected to
+find. The §Inverted§ property is set only if the exception came
+from a §MatchNot(...)§ operation. In this case, the §CharSet§
+property contains the values, that the lexer must §not§ match. The
+validity of pro\-per\-ti\-es are shown in the next table,
+depending on the kind of exception.
+
+\begin{table}[H]
+  \small
+  \begin{center}
+      \begin{tabular}{lcc}
+                        & Mismatched char   & Mismatched string \\
+         \hline
+         FoundChar      &  valid            & -                 \\
+         FoundString    &   -               & valid             \\
+         CharSet        &  valid            & -                 \\
+         Str            &   -               & valid             \\
+         Inverted       &  valid            & -                 \\
+         \hline
+      \end{tabular}
+  \end{center}
+\end{table}
+
+\subsection{EdpgMismatchedToken}
+The §EdpgMismatchedToken§ exception is thrown by the parser when
+it is looking for a token, but finds a different one on the input
+token stream than expected. It defines the following properties in
+addition to those of §EdpgException§.
+\begin{alltt}
+   FoundToken   : IdpgToken;
+   TokenSet     : TdpgByteSet;
+   Inverted     : boolean;
+\end{alltt}
+The §FoundToken§ property contains the token the parser received from the
+lexer. The §TokenSet§ property contains the vaules the parser expected to
+get. The §Inverted§ property is set only if the exception came from a
+§MatchNot(...)§ operation. In this case, the §TokenSet§ property contains the
+values the parser must §not§ get.
+
+\subsection{EdpgSemantic}
+This exception is thrown by a validating semantic predicate. It
+defines the following property in addition to those of
+§EdpgException§.
+\begin{alltt}
+   Assert : string;
+\end{alltt}
+The §Assert§ property contains the validating expression that caused the
+exception.