[Haskell-cafe] Class/Instance : what am I doing wrong in this example ?

[david48]

On Dec 20, 2007 5:36 PM, Jules Bean <jules at jellybean.co.uk> wrote:
> 2. Maybe you want lots of possible different "a"s for each "g". Then you
> make "a" a parameter of the class too.

> 3. Maybe you want just one particular "a" for each "g". I.e. "g"
> determines "a". Then you can proceed as for (2), but add the functional
> dependency | g -> a

Practically, what would be the difference between 2. and 3. ?

David.