On Wed, Nov 09, 2011 at 11:42:27PM +0100, Waldek Hebisch wrote:
> [..]
> > > Spad allows much heavier overloading then is possible in Haskell.
> > > [..]
> >
> > Haskell has much of overloading. I do not know of any example of what
> > needs more overloading. May be, you give such?
>
> Well:
>
> 1) Let r be elements of a Ring R and v element of module over R.
> r*v, r*r, v*r are legal, call different functions (and the
> function are not related by inheritance) while v*v is
> illegal. AFAICS it is impossible to get such result via
> inheritance.
Yes.
The DoCon library puts (in Haskell) something like
class (Ring r, AdditiveGroup v) => Module r v
where
cMul :: r -> v -> v
It fails to use (*) here.
On the other hand, in my experience, the summary negative effect of this
is small.
I thank Waldek Hebisch and other people for helpful notes.
------
Sergei
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