<h3>Introduction to IxSet</h3>
<p>There's another utility package included in the Happstack suite, happstack-ixset, which you might find useful</p>
<p>In a nutshell, the package provides a module Happstack.Data.IxSet, that defines a new data type which acts
an awful lot like the old familiar Data.Map but allows you to easily select subsets based upon component data.</p>
<p>An example is included with this tutorial at <a href="/src/IxSetExample.hs">IxSetExample.hs</a>.</p>
<p>I suggest reading over the code included to supplement the haddock documentation for Happstack.Data.IxSet and
playing with all of the values starting with "ex" to make sure you feel comfortable with the values they have and why.</p>
<p>I make no attempt to cover all of the combinators defined in Happstack.Data.IxSet, but I hope I cover enough of them
to give you a good start.</p>
<p>A final note about IxSet is that if the contained type is an instance of Serialize, then the entire IxSet will
be an instance of Serialize thus making it suitable for use with Happstack.State<p>