Re: [Haskell-cafe] [ANN] relational-record - relational-algebraic query building DSL

On Fri, Dec 19, 2014 at 4:44 AM, Tom Ellis wrote:

Opaleye uses arrows only because it is hard to implement a sensible semantics otherwise. See, for example, this bug report on HaskellDB which used a monad rather than an arrow

I'm curious how arrows make it easier to deal with aggregation? Sounds pretty interesting ... Justin