Help need "Cannot use type synonym in instance head"
Benny
neon_2001@hotmail.com
Sun, 14 Apr 2002 16:22:36 +1200
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type Poly =3D [Float]
addPoly::Poly->Poly->Poly
addPoly x y =3D zipWith (+) x y
instance (Float a) =3D> Num (Poly a) where
(+) =3D addPoly
I got the error message "Cannot use type synonym in instance head" when =
I was trying to compile the codes above. Can anyone tell me why and how =
to solve it?
Cheers
Benny
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<DIV><FONT face=3DMingLiu size=3D2>type Poly =3D [Float]</FONT></DIV>
<DIV><FONT face=3DMingLiu size=3D2></FONT> </DIV>
<DIV><FONT face=3DMingLiu =
size=3D2>addPoly::Poly->Poly->Poly<BR>addPoly x y =3D=20
zipWith (+) x y</FONT></DIV>
<DIV><FONT face=3DMingLiu size=3D2></FONT> </DIV>
<DIV><FONT face=3DMingLiu size=3D2>instance (Float a) =3D> Num (Poly =
a)=20
where<BR> &nbs=
p; =20
(+) =3D addPoly</FONT></DIV>
<DIV><FONT face=3DMingLiu size=3D2></FONT> </DIV>
<DIV><FONT face=3DMingLiu size=3D2></FONT> </DIV>
<DIV><FONT face=3DMingLiu size=3D2>I got the error message "Cannot use =
type synonym=20
in instance head" when I was trying to compile the codes above. Can =
anyone tell=20
me why and how to solve it?</FONT></DIV>
<DIV><FONT face=3D=B2=D3=A9=FA=C5=E9 size=3D2></FONT> </DIV>
<DIV><FONT face=3D=B2=D3=A9=FA=C5=E9 size=3D2>Cheers</FONT></DIV>
<DIV><FONT face=3D=B2=D3=A9=FA=C5=E9 size=3D2></FONT> </DIV>
<DIV><FONT face=3D=B2=D3=A9=FA=C5=E9 =
size=3D2> Benny</FONT></DIV></BODY></HTML>
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