old_s = Container.find old_sdx nl
int_p = Node.removePri old_p inst
int_s = Node.removeSec old_s inst
- new_p = Node.addPri int_s inst
- new_s = Node.addSec int_p inst old_sdx
- new_nl = if isNothing(new_p) || isNothing(new_s) then Nothing
- else Just $ Container.addTwo old_pdx (fromJust new_s)
- old_sdx (fromJust new_p) nl
+ new_nl = do -- Maybe monad
+ new_p <- Node.addPri int_s inst
+ new_s <- Node.addSec int_p inst old_sdx
+ return $ Container.addTwo old_pdx new_s old_sdx new_p nl
in (new_nl, Instance.setBoth inst old_sdx old_pdx, old_sdx, old_pdx)
-- Replace the primary (f:, r:np, f)
tgt_n = Container.find new_pdx nl
int_p = Node.removePri old_p inst
int_s = Node.removeSec old_s inst
- new_p = Node.addPri tgt_n inst
- new_s = Node.addSec int_s inst new_pdx
- new_nl = if isNothing(new_p) || isNothing(new_s) then Nothing
- else Just $ Container.add new_pdx (fromJust new_p) $
- Container.addTwo old_pdx int_p
- old_sdx (fromJust new_s) nl
+ new_nl = do -- Maybe monad
+ new_p <- Node.addPri tgt_n inst
+ new_s <- Node.addSec int_s inst new_pdx
+ return $ Container.add new_pdx new_p $
+ Container.addTwo old_pdx int_p old_sdx new_s nl
in (new_nl, Instance.setPri inst new_pdx, new_pdx, old_sdx)
-- Replace the secondary (r:ns)
old_s = Container.find old_sdx nl
tgt_n = Container.find new_sdx nl
int_s = Node.removeSec old_s inst
- new_s = Node.addSec tgt_n inst old_pdx
- new_nl = if isNothing(new_s) then Nothing
- else Just $ Container.addTwo new_sdx (fromJust new_s)
- old_sdx int_s nl
+ new_nl = Node.addSec tgt_n inst old_pdx >>=
+ \new_s -> return $ Container.addTwo new_sdx
+ new_s old_sdx int_s nl
in (new_nl, Instance.setSec inst new_sdx, old_pdx, new_sdx)
-- Replace the secondary and failover (r:np, f)
tgt_n = Container.find new_pdx nl
int_p = Node.removePri old_p inst
int_s = Node.removeSec old_s inst
- new_p = Node.addPri tgt_n inst
- new_s = Node.addSec int_p inst new_pdx
- new_nl = if isNothing(new_p) || isNothing(new_s) then Nothing
- else Just $ Container.add new_pdx (fromJust new_p) $
- Container.addTwo old_pdx (fromJust new_s)
- old_sdx int_s nl
+ new_nl = do -- Maybe monad
+ new_p <- Node.addPri tgt_n inst
+ new_s <- Node.addSec int_p inst new_pdx
+ return $ Container.add new_pdx new_p $
+ Container.addTwo old_pdx new_s old_sdx int_s nl
in (new_nl, Instance.setBoth inst new_pdx old_pdx, new_pdx, old_pdx)
-- Failver and replace the secondary (f, r:ns)
tgt_n = Container.find new_sdx nl
int_p = Node.removePri old_p inst
int_s = Node.removeSec old_s inst
- new_p = Node.addPri int_s inst
- new_s = Node.addSec tgt_n inst old_sdx
- new_nl = if isNothing(new_p) || isNothing(new_s) then Nothing
- else Just $ Container.add new_sdx (fromJust new_s) $
- Container.addTwo old_sdx (fromJust new_p)
- old_pdx int_p nl
+ new_nl = do -- Maybe monad
+ new_p <- Node.addPri int_s inst
+ new_s <- Node.addSec tgt_n inst old_sdx
+ return $ Container.add new_sdx new_s $
+ Container.addTwo old_sdx new_p old_pdx int_p nl
in (new_nl, Instance.setBoth inst old_sdx new_sdx, old_sdx, new_sdx)
checkSingleStep :: Table -- ^ The original table