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converter for Maybe type

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This commit is contained in:
Scott R. Parish 2010-03-08 07:01:32 -06:00
parent 3c0b57db7c
commit 34599280f5
1 changed files with 6 additions and 0 deletions
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6
Database/MongoDB/BSON.hs
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@ -567,3 +567,9 @@ instance BsonConv [BsonDoc] where
toBson = BsonArray . List.map toBson
fromBson (BsonArray ss) = List.map fromBson ss
fromBson _ = throwUnsupConv
instance (BsonConv a) => BsonConv (Maybe a) where
toBson Nothing = BsonNull
toBson (Just a) = toBson a
fromBson BsonNull = Nothing
fromBson a = Just $ fromBson a