gistfile1.hs

-- | From a list of account names, select those which are direct                                                                                                                   
-- subaccounts of the given account name.                                                                                                                                          
subAccountNamesFrom ∷ [AccountName] → AccountName → [AccountName]
subAccountNamesFrom accts a = filter (`isSubAccountNameOf` a) accts

accountNameTreeFrom accts =
   Node "top" $ unfoldForest (λa → (a, subs a)) $ topAccountNames accts
        where
          subs = subAccountNamesFrom allaccts
          allaccts = expandAccountNames accts

          -- subs' a = subsmap ! a                                                                                                                                                 
          -- subsmap :: Map AccountName [AccountName]                                                                                                                              
          -- subsmap = Data.Map.fromList [(a, subAccountNamesFrom allaccts a) | a <- allaccts]