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byorgey/Knotty.hs

Created October 13, 2012 16:01
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Creating a tree with shared links back to parent nodes
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Knotty.hs
type AccountName = String
data Account = Account {
aname :: AccountName,
asubs :: [Account]
}
deriving Show
data Account2 = Account2 {
aname2 :: AccountName,
aparent2 :: Maybe Account2,
asubs2 :: [Account2]
}
tie :: Account -> Account2
tie = tie' Nothing
where
tie' parent (Account nm subs)
= let acct = Account2 nm parent (map (tie' (Just acct)) subs)
in acct
exAcct =
Account "foo" [Account "bar" [Account "baz" []], Account "quux" []]
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byorgey commented Oct 13, 2012

Here's a visualization of tie exAcct after being fully evaluated, using ghc-vis:

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