Another problem is have is to filter entries in a map. If I have a map<br><br>Ord k =&gt; Map k [a]<br><br>(essentially, which combines data with the same key into a list)<br><br>and I have a predicte  (k,a) -&gt; Bool<br>
<br>(which takes the key and one element in its list and checks it)<br><br>and I need to regenerate the map, what would be a good way to do that?<br><br><br><br>