HaXml

HaXml is a collection of utilities for parsing, filtering, transforming, and generating Extensible Markup Language documents using the programming language Haskell.

Overview

HaXml utilities include:

XML parser
XML validator
a separate error-correcting parser for HTML
pretty-printers for XML and HTML
stream parser for XML events
translator from DTD to Haskell
translator from XML Schema definitions to Haskell data types

HaXml provides a combinator library with a set of higher-order functions which process the XML documents after they are represented using the native Haskell data types. The basic data type is Content which represents the document subset of XML.
HaXml allows converting XML to Haskell data and vice versa, and XML to XML. The common use of the HaXml's parser includes defining the method of traversing the XML data and it has the CFilter type, where type CFilter = Content -> . It means that this function defined by the user will take a fragment of an XML data and either return more fragments or none at all. This approach allows to choose XML elements satisfying certain conditions.

Example

In the chapter 22 "Extended Example: Web Client Programming" of the Real World Haskell by Bryan O'Sullivan, Don Stewart, and John Goerzen, the following example is considered. The XML file looks like this :

Haskell <a href="/wiki/Radio">Radio</a>
http://www.example.com/radio/
Description of this podcast
First item
Second item

The following content filter is constructed:

channel :: CFilter
channel = tag "rss" /> tag "channel"

This filter is later used to get the title of the channel:

getTitle :: Content -> String
getTitle doc = contentToStringDefault "Untitled Podcast"