I think I finally found the cause of a key laziness bug in reactive.&nbsp; It took me a long time to track down.&nbsp; The way I structured the AddBounds type stops me from getting partial info I need.&nbsp; There&#39;s a critical max on times in joinE.&nbsp; It&#39;ll be &#39;max (NoBound t0) ta&#39;, and I know that ta is either a NoBound or a MaxBound, but without knowing which, no info can come out, which stops the consumer of that max from knowing that the time is at least NoBound t0.&nbsp; Now I think I have to make some pervasive changes to reactive.<br>
<br>I&#39;d like to develop the QC tests that will catch these mistakes much earlier.&nbsp;&nbsp; I recently read the &quot;Chasing Bottoms&quot; paper, which some good techniques.<br><br>&nbsp;&nbsp; - Conal<br><br>