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>Design and Implementation of a validating XML parser in Haskell: Master's thesis; 
			University of Applied Sciences Wedel
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>Chapter 3. Package hparser</TD
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>3.2. Module HdomParser</H1
><P
>&#13;		The module <TT
CLASS="classname"
>HdomParser</TT
> provides functions for parsing XML files and building the generic tree data structure <TT
CLASS="literal"
>XmlTree</TT
> from these documents. The whole parsing process takes place in the State-I/O monad of the module <TT
CLASS="classname"
>XmlState</TT
>, so that well-formedness errors can be reported and different computations can be traced by outputting their results.
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><B
>Parse functions</B
></P
><DL
><DT
><TT
CLASS="function"
>parseDoc :: String -&#62; IO [XmlTree]</TT
></DT
><DD
><P
>&#13;					Parses the file specified by the first parameter.
					</P
></DD
><DT
><TT
CLASS="function"
>parseXmlFile :: IO [XmlTree]</TT
></DT
><DD
><P
>Parses an XML file specified by a command line argument:
					<P
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><UL
><LI
><P
>--source "source file" - XML file to parse</P
></LI
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><P
>--encoding "encoding" - Encoding scheme used in the file (optional)</P
></LI
></UL
>
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>&#13;		The following example shows how an XML parser is constructed in the module <TT
CLASS="classname"
>HdomParser</TT
>. The whole parsing process takes place in the State-I/O monad defined in the module <TT
CLASS="classname"
>XmlState</TT
>. All computations are of type <TT
CLASS="literal"
>XmlStateFilter</TT
>.
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>&#13;processXmlN	:: Int -&#62; XmlTree -&#62; IO [XmlTree]
processXmlN n t0
    = run' $ do
             setSysState (selXTagAttrl . getNode $ t0)
             setTraceLevel n
             t1 &#60;- getXmlContents $ t0
             t2 &#60;- parseXmlDoc    $$&#60; t1
             t3 &#60;- liftM transfAllCharRef $$&#60; t2
             t4 &#60;- processDTD     $$&#60; t3
             t5 &#60;- processGeneralEntities $$&#60; t4
             el &#60;- getErrorLevel
             return ( if el == 0
                      then t5
                      else [] )
		</PRE
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>Actions during parsing</B
></P
><DL
><DT
><TT
CLASS="function"
>getXmlContents :: XmlStateFilter a</TT
></DT
><DD
><P
>&#13;					 Returns a filter for reading the XML file. The filename is retrieved from the attribute with the name "<SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>source</I
></SPAN
>" which must be part of the initial node <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>t0</I
></SPAN
>.
					</P
></DD
><DT
><TT
CLASS="function"
>parseXmlDoc :: XmlStateFilter a</TT
></DT
><DD
><P
>&#13;					Parses the XML file and builds the <TT
CLASS="literal"
>XmlTree</TT
>.
					</P
></DD
><DT
><TT
CLASS="function"
>transfAllCharRef :: XmlFilter</TT
></DT
><DD
><P
>&#13;					The <TT
CLASS="literal"
>XmlFilter</TT
> <TT
CLASS="function"
>transfAllCharRef</TT
> has to be lifted to an <TT
CLASS="literal"
>XmlStateFilter</TT
>. The filter substitutes character references by their characters.
					</P
></DD
><DT
><TT
CLASS="function"
>processDTD :: XmlStateFilter a</TT
></DT
><DD
><P
>&#13;					 Substitutes parameter entities, adds include sections and removes exclude sections of DTDs, merges internal and external DTD subsets.
					</P
></DD
><DT
><TT
CLASS="function"
>processGeneralEntities :: XmlStateFilter a</TT
></DT
><DD
><P
>&#13;					 Substitutes general entities.
					</P
></DD
><DT
><TT
CLASS="function"
>getErrorLevel :: XState state Int</TT
></DT
><DD
><P
>&#13;					 If an error occurred during applying the <TT
CLASS="literal"
>XmlStateFilter</TT
>s, <TT
CLASS="function"
>&#13;					 processXmlN</TT
> returns an empty list, otherwise it returns the constructed <TT
CLASS="literal"
>XmlTree</TT
>.
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