README.md
1[](https://travis-ci.org/HeinrichApfelmus/vault)
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4*Vault* is a tiny library that provides a single data structure called *vault*.
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6A *vault* is a type-safe, persistent storage for values of arbitrary types. Like `IORef`, I want to be able to store values of any type in it, but unlike `IORef`, I want the storage space to behave like a persistent, first-class data structure, as appropriate for a purely functional language.
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8It is analogous to a bank vault, where you can access different bank boxes with different keys; hence the name.
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10In other words, a vault is an abstract data type with the following basic signature
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12 data Key a
13 data Vault
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15 newKey :: IO (Key a)
16 empty :: Vault
17 lookup :: Key a -> Vault -> Maybe a
18 insert :: Key a -> a -> Vault -> Vault
19 delete :: Key a -> Vault -> Vault
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21A few common functions for finite maps, like `adjust` and `union`, are provided as well.
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24This library was created thanks to the feedback on my blog post [Vault - a persistent store for values of arbitrary types][1].
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26 [1]: http://apfelmus.nfshost.com/blog/2011/09/04-vault.html
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29Installation
30============
31The whole thing is [available on hackage][hackage], so you just have to type
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33 cabal update
34 cabal install vault
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36 [hackage]: http://hackage.haskell.org/package/vault
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38Feedback
39========
40Use the [issue tracker][2] or send an [email to the maintainer][3].
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42 [2]: https://github.com/HeinrichApfelmus/vault/issues
43 [3]: mailto:apfelmus@quantentunnel.de
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