Hi all,
I have some program data that I'd like to persist. I could just
use read and show and file I/O to store arrays as files. [1] This
works and it is easy and simple (which I like) but it is also
inefficient and a little cumbersome.
I imagine that this is a very common task, and I know of utilities
in other environments like object databases, embedded databases, XML
persistence, etc. that can make this kind of persistence simple *and*
relatively efficient and reliable. E.g.) I have found the HSQLDB
embedded database [2] to be useful when writing Java applications.
What do you do for quick and easy persistence in Haskell? Are there
any libraries or techniques that are especially useful for this?
[1]
> type SimpleRecord = (Integer, Integer, Integer)
> type SimpleIndex = Integer
> type SimpleDB = (Array SimpleIndex SimpleRecord, FilePath)
> loadDB :: FilePath -> IO SimpleDB
> loadDB f = do h <- openFile f ReadMode
> s <- hGetContents h
> hClose h
> return $ r s
> where r :: String -> SimpleDB
> r = read
> getRecord :: SimpleDB -> SimpleIndex -> SimpleRecord
> getRecord (a, _) = (a !)
> updateRecord :: SimpleDB -> SimpleIndex -> SimpleRecord -> SimpleDB
> updateRecord (a, f) i r = (a//[(i,r)],f)
> storeDB :: SimpleDB -> IO ()
> storeDB sdb@(a,f) = do h <- openFile f WriteMode
> hPutStr h (show sdb)
> hClose h
> sampleDB = (array (0,10) [(x,(x+1,x*2,42)) | x <- [0..10]],"output/
1.db.txt")
[2] http://hsqldb.org/
- Matt Munz
[EMAIL PROTECTED]
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