Cookbooks
Haskell
Chapter 10. Data Formats and Serialization
Working with XML

Haskell:
Working with XML

How to:

Haskell offers libraries like xml-conduit for dealing with XML. The following example demonstrates parsing an XML string and querying elements:

{-# LANGUAGE OverloadedStrings #-}

import qualified Data.Text as T
import Text.XML
import Text.XML.Cursor

main :: IO ()
main = do
  let xmlContent = "<greetings><hello>World!</hello></greetings>"
  let document = parseLBS_ def $ T.encodeUtf8 $ T.pack xmlContent
  let cursor = fromDocument document

  let helloTexts = cursor $// element "hello" &/ content
  print helloTexts  -- ['World!']

Sample output:

["World!"]

Deep Dive

XML, short for eXtensible Markup Language, has been a staple in data serialization long before JSON’s ascent. It’s verbose, but rigid and standardized, making it suitable for strict enterprise environments, legacy systems, and industries like finance and healthcare.

Haskell has several libraries for XML; however, xml-conduit is among the most powerful and widely-used due to its efficient streaming and parsing capabilities, part of the conduit family for handling data streams.

Alternatives include HXT (Haskell XML Toolbox) which uses arrows for parsing and transformation, providing a different paradigm for XML manipulations. Although HXT is less popular now due to its steeper learning curve, it still remains a solid choice for some use cases.

When implementing XML processing in Haskell, you have to care about encoding, as Haskell strings are Unicode and XML data might not be. Additionally, XML namespaces can add extra complexity to parsing.

See Also:

Working with TOMLWorking with YAML