what's the difference?
Cagdas Ozgenc
co19@cornell.edu
Thu, 11 Jul 2002 13:44:25 +0300
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Greetings.
What is the difference between the following two scenarios:
1)
class Eq a where=20
(=3D=3D) :: a -> a -> Bool
class Eq a =3D> Ord a where
( < ) :: a -> a -> Bool
2)
class Eq a where
(=3D=3D) :: a -> a -> Bool
class Ord a where
(eq),( < ) :: a -> a -> Bool
instance Ord a =3D> Eq a where
(=3D=3D) =3D eq
eq is just a rename for =3D=3D to avoid the nameclash
The second scenario resembles Russell's Paradox. Typeclass of a =
typeclass. Anyhow we are loosing orthogonality here.
Thanks
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<BODY bgColor=3D#ffffff>
<DIV><FONT face=3DArial size=3D2>Greetings.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>What is the difference between the =
following two=20
scenarios:</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>1)</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>class Eq a where </FONT></DIV>
<DIV><FONT face=3DArial size=3D2> (=3D=3D) :: a -> =
a ->=20
Bool</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>class Eq a =3D> Ord a =
where</FONT></DIV>
<DIV><FONT face=3DArial size=3D2> ( < ) :: a -> =
a ->=20
Bool</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>2)</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>class Eq a where</FONT></DIV>
<DIV><FONT face=3DArial size=3D2> (=3D=3D) :: a -> =
a ->=20
Bool</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>class Ord a where</FONT></DIV>
<DIV><FONT face=3DArial size=3D2> (eq),( < ) :: a =
-> a ->=20
Bool</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>instance Ord a =3D> Eq a =
where</FONT></DIV>
<DIV><FONT face=3DArial size=3D2> (=3D=3D) =3D =
eq</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>eq is just a rename for =3D=3D to avoid =
the=20
nameclash</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>The second scenario resembles Russell's =
Paradox.=20
Typeclass of a typeclass. Anyhow we are loosing orthogonality =
here.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>Thanks</FONT></DIV></BODY></HTML>
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