Hi,
I'm not sure what you are after, but:
data Secret a = Secret {password :: String, value :: a}
classify :: String -> a -> Secret a
classify = Secret
declassify :: String -> Secret a -> Maybe a
declassify guess (Secret pw v) | guess == pw = Just v
| otherwise = Nothing
Put that in a module, do not export the Secret data type, and you're
good to go. I'm unsure what a Monad is giving you....
Thanks
Neil
On 10/10/06, Seth Gordon <[EMAIL PROTECTED]> wrote:
Cale Gibbard wrote:
> Why not just:
>
> secret :: a -> Classification String a
> secret = Classification "xyzzy"
>
> The password string isn't part of the type, it doesn't even
> necessarily exist at compile time. You might have just got confused
> between type and data constructors for a moment.
>
But now I want to be able to process the secret monadically:
mySecret =
secret "Jimmy Hoffa is buried under the 50-yd line in the Meadowlands"
do secretData <- mySecret
return (length secretData)
How do I define "return" so that it will put the password back, and how
do I define "(>>=)" so that the password won't be accessible within the
do-block?
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