niceTransDbAlgebras.hs

type TransId = Integer
data State -- AffineSpace wh Diff is just a Monoid (name?), Diff State ~ Trans
data Trans -- Monoid
data Query -- JoinSemilattice
runTrans :: Trans -> State -> State -- modifies the state arbitrarily
runQuery :: Query -> State -> State -- selects a subset of the state


forceCommit :: Trans -> m Bool
tryCommit :: TransId -> Trans -> m Bool
lastTrans :: m TransId
query :: TransId -> Query -> State

-- Relation to get/set and lenses
-- Query as Getter (s -> a)
-- Trans as Setter (s -> b -> t)