I have a base class,Organization, with name and address functions.
I want classes Buyer and Seller from Organization.
Now if I want to create an 2 instances of Seller
> data Yahoo = Yahoo
> instance Organization Yahoo where
> name _= "Yahoo"
> addreess = ...
> data DoubleClick= DoubleClick
> instance Organization DoubleClick where
> name _ = "DoubleClick"
...
Why is [Yahoo,DoubleClick] illegal?
----
Another approach is to do
> data Organization = Org {
> name,address::String
> }
> data Seller = Seller {
> org::Organization
> askPrice::Int
> }
yahoo = Seller (Org "Yahoo" "California") 12
But, that requires you to access
nameYahoo = name org yahoo
when it would make more sense to do
nameYahoo = name yahoo
-----------
It also prevents you from making a list of buyers and sellers that doesn't
lose information.
> func::Organization->Int
> func (Buyer=>b) b = bidPrice b
> func (Seller=>s) s = askPrice s
> result = map func organizationList
should work, I think.
-Alex-
___________________________________________________________________
S. Alexander Jacobson i2x Media
1-212-697-0184 voice 1-212-697-1427 fax
