Re: [Haskell-cafe] Does this typeclass have a name?

On 2014-04-21 09:04, Ivan Lazar Miljenovic wrote:

On 21 April 2014 15:09, Bardur Arantsson wrote:

...

Hi all,

I was wondering if anyone out there knows if this type class has a name?

class Foo a e where foo :: e -> a -> a bar :: a

(I also have a fundep a -> e, but that's not essential.)

Essentially the usage is:

You have a sequence of "events" e_i and a starting value "bar" and can use the "foo" function to apply all events to that starting value

foo e_n $ foo e_{n-1} $ ... $ foo e_0 $ bar

= foldr foo bar [e_n, e_{n-1} .. e_0] ?

Yes, indeed, but I want the type class to constrain things since there are other interacting constraints on the types "a" and "e" (plus there's the fundep that I mentioned). The "single instance" part of type classes is also very desirable. Regards,