How overload operator in Haskell?

[Liu Junfeng]

I come up a solution as this:
---------------------------------------------------
module Vector where
data Vector =3DVector [Double]
fromVector :: Vector -> [Double]
fromVector (Vector v) =3D v
fromList :: [Double] -> Vector
fromList v =3D Vector v
toVector :: Double -> Vector
toVector x =3D Vector (repeat x)
instance Eq Vector where
   v1 =3D=3Dv2 =3D (fromVector v1) =3D=3D (fromVector v2)
instance Show Vector where
   show v =3D show (fromVector v)
instance Num Vector where
   v1 + v2 =3DVector (zipWith (+) (fromVector v1) (fromVector v2))
   v1 - v2 =3DVector (zipWith (-) (fromVector v1) (fromVector v2))
   v1 * v2 =3DVector (zipWith (*) (fromVector v1) (fromVector v2))
   signum v =3D Vector (map signum (fromVector v))
   abs v =3D Vector ((repeat.sqrt.sum.fromVector) (v*v))
   fromInteger n =3DVector (repeat (fromInteger n))
instance Fractional Vector where
    v1 / v2 =3D Vector (zipWith (/) (fromVector v1) (fromVector=
 v2))
    fromRational r =3DVector (repeat (fromRational r))
-----------------------------------------------------------------=
---------
rk4 ::=
 ((Vector,Vector)->Vector)->Vector->Vector->Vector->[Vector]
rk4 _ _ _ (Vector []) =3D []
rk4 f h y0 (Vector (x0:xs)) =3D y0  :rk4 f h y1 (Vector xs) where=
 y1=3Dyp f h (toVector x0) y0
yp ::((Vector,Vector)->Vector)->Vector->Vector->Vector->Vector
yp f h x y =3D y +  (k1 + 2 * (k2 + k3) + k4)
     where k1=3Dh*f(x,y)
           k2=3Dh*f(x+0.5*h, y +(0.5*k1))
           k3=3Dh*f(x+0.5*h, y +(0.5*k2))
           k4=3Dh*f(x+h, y+k3)

a=3Dlet g (x,y1) =3D y1
      x0 =3D 0
      h =3D 0.01
      x =3DVector [x0,x0+h..3]
      y0 =3DVector [0,0.5]
   in rk4 g (toVector h) y0 x
-----------------------------------------------------------------=
---------

The main problem is how to make type convert implicitly.
Whem a function needs a vector as its parameter, pass a double=
 and it is 
converted to vector implicitly. 

=3D=3D=3D=3D=3D=3D=3D 2003-07-12 12:18:00 Jon Fairbairn Wrote=A3=BA=3D=3D=3D=3D=3D=3D=3D

>On 2003-07-12 at 20:20+1000 Andrew J Bromage wrote:
>> G'day all.
>> 
>> On Fri, Jul 11, 2003 at 04:28:19PM -0400, Dylan Thurston=
 wrote:
>> 
>> > Don't be silly [...]
>> 
>> Never!
>
>Or only sometimes. I'm surprised that no-one has yet
>answered the question "How overload operator in Haskell?"
>with "Overload operator in Haskell fine". (cf Cary Grant)

I am also surprised at this, it can be done by C++ .
>
>-- 
>J=F3n Fairbairn                                =
 Jon.Fairbairn@cl.cam.ac.uk
>31 Chalmers Road                                        =
 jf@cl.cam.ac.uk
>Cambridge CB1 3SZ            +44 1223 570179 (after 14:00 only,=
 please!)
>
>
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=3D =3D =3D =3D =3D =3D =3D =3D =3D =3D =3D =3D =3D =3D =3D =3D =3D =3D =3D =3D
=09=09=09

Regards,=09=09=09=09 
Liu Junfeng
liujf@softhome.net
2003-07-12