prefix :: (FlaggedDeps comp qpn -> FlaggedDep comp' qpn) -> [FlaggedDeps comp qpn] -> FlaggedDeps comp' qpn
prefix _ []  = []
prefix :: (FlaggedDeps comp qpn -> FlaggedDep comp' qpn) -> [FlaggedDeps comp qpn] -> FlaggedDeps comp' qpn
prefix _ []  = []
prefix _ []  = []