Right, to fully evaluate something you'd use Deepseq. With data structures like Data.HashMap.Strict, Data.Text, etc., the HNF gained from strict data fields ten

Right, to fully evaluate something you'd use Deepseq. With data structures like Data.HashMap.Strict, Data.Text, etc., the HNF gained from strict data fields tends to be sufficient to avoid most issues caused by space leaks -- but even for something like !String, i.e. ![Char], you'd have to try pretty hard to blow up the stack. (Evaluating the first cell is also more useful than it might seem at first glance.) I find myself using deepseq the most when I want to be sure a data structure (and any exceptions any pending operations might throw) has been fully evaluated before passing it off to another thread, not to prevent space leaks.