glad that helped, definitely helped me
On Tue, Jan 27, 2015 at 3:29 PM, David Turner wrote: On 27 January 2015 at 17:23, Charles Durham You need to sign up for it, but this is a phenomenal talk by simon peyton
jones describing the idea behind lenses the way he understood it. https://skillsmatter.com/skillscasts/4251-lenses-compositional-data-access-a... Thanks, I think that was exactly what I needed to know. If I understand the key section right, you can do all that stuff with
a straight get/set pair but it'd be desperately inefficient, so then
you add an update function, and then one at Maybe and [] and IO and
they all start to look the same so you generalise to all Functors, and
then you discover that using Const you get a getter, and Identity
gives you a setter, so you can throw them away and end up with a lens
as we know it. And then you generalise it in about a billion other directions and you
end up with the lens library! Much obliged, David