[Haskell-cafe] a monad for secret information

[Felipe Almeida Lessa]

2006/10/10, David Roundy <droundy at darcs.net>:
>
>
> >declassify :: Secret a -> String -> Maybe a
> >declassify (Secret pw x) pw' | pw' == pw = Just x
> >declassify (Secret _ _) _ = Nothing


Why does this works? "Yet Another Haskell Tutorial" teaches that pattern
matching occurs at one stage and guard processing at other, and that there's
no back (page 94).

-- 
Felipe.
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