a) i think that continuous auctions have a bunch of vulnerabilities and that for exchanges, a periodic crossing might be a better mechanism. this works better f

a) i think that continuous auctions have a bunch of vulnerabilities and that for exchanges, a periodic crossing might be a better mechanism. this works better for high volume instruments. it does come at the expense of immediate trading b) is it possible to make all the transactions in a block go "at once"? ie if any tx have some sequential interdependence, kick one and make it wait for the next block?