úÎϺFChecks whether Control.Exception.evaluate (or rwhnf) would do no work K when applied to the value. May produce false negatives (where isEvaluated ( thinks it would, but it actually wouldn't) in some cases. HUse case: if isEvaluated foo returns True, then evaluate foo will never E throw an exception, or indeed take more than constant (small) time. isevaluated-0.2Data.IsEvaluated isEvaluated