I've thought about bidirectional value propagation too, but except for cases where no information is lost (e.g. cons) I'm similarly stumped (e.g. append). I'v

I've thought about bidirectional value propagation too, but except for cases where no information is lost (e.g. cons) I'm similarly stumped (e.g. append). I've got bidirectional type propagation working though. There are bidirectional logic gates, e.g. Fredkin gate, but they operate on individual bits.