Monad Maybe?

[Dylan Thurston]

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On Sat, Sep 21, 2002 at 12:56:13PM -0700, Russell O'Connor wrote:
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>=20
> [To: haskell-cafe@haskell.org]
>=20
> Is there a nicer way of writing the following sort of code?
>=20
> case (number g) of
>  Just n -> Just (show n)
>  Nothing ->
>   case (fraction g) of
>    Just n -> Just (show n)
>    Nothing ->
>     case (nimber g) of
>      Just n -> Just ("*"++(show n))
>      Nothing -> Nothing

You could write (using GHC's pattern guards):

show g | Just n =3D number g   =3D Just (show n)
       | Just n =3D fraction g =3D Just (show n)
       | Just n =3D nimber g   =3D Just ("*"++show n)
       | Nothing             =3D Nothing

Do I detect a program for analyzing combinatorial games being written?

--Dylan

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