Proposal: refactor Arrow class

[wren ng thornton]

On 7/16/12 3:44 PM, Twan van Laarhoven wrote:
>I am sure there are other examples of categories for which
> `arr` is too strong, but which do, for example, support `first`.

My major complaint with arrows has always been that `arr` is way too 
strong. By requiring that we can embed every Haskell function into a 
given arrow we eliminate countless "arrows" which obey all the rest of 
the interface but which are specifically limited in not representing all 
Haskell functions. I'm thinking for example of DSLs. Ofttimes the whole 
point of a given DSL is that by restricting to a well-behaved class of 
functions we can get performance or other reasoning benefits.

-- 
Live well,
~wren