Safe Haskell is a GlasgowHaskellCompiler extension to the Haskell language which allows unsafe (or simply untrusted) code to be used safely from within a trusted codebase, by restricting which Haskell/GHC features the untrusted code may use.

Code may be marked as

	Safe:	does not use unsafe features.
	Trusted:	uses unsafe features but in such a way that the details are safely encapsulated and are not accessible via the public api.
	Unsafe:	uses unsafe features in a way which could taint any code which imports it.

http://www.haskell.org/ghc/docs/7.2.1/html/users_guide/safe-haskell.html
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CategoryHaskell CategorySafety TypeSafe