And still haven't. The most interesting attempts, like Ed Ashcroft's and Bill Wadge's Lucid, seem to have withered. It's not clear to me whether that was becaus

And still haven't. The most interesting attempts, like Ed Ashcroft's and Bill Wadge's Lucid, seem to have withered. It's not clear to me whether that was because they didn't offer enough that was different, or it was too hard to make the implementations efficient, or both. And yet it all does still "look very interesting".