On Fri, Jun 5, 2015 at 3:47 AM, Keean Schupke <ke...@fry-it.com> wrote: > > > On 5 June 2015 at 11:36, Matt Rice <ratm...@gmail.com> wrote: >> >> On Fri, Jun 5, 2015 at 2:46 AM, Keean Schupke <ke...@fry-it.com> wrote: >> > I don't understand, you just use type-classes: >> > >> > area :: (RightTriangle a b, Numeric b) => a -> b >> > >> > RightTrianlge is a constraint on the polygon "a" with points of type "b" >> > (Int or Float etc). >> > >> > Only the algorithm used in areaOfRightTriangle knows the type of >> > triangle >> > required for the area operation, not the triangle itself. >> > >> > I can have other triangle area definitions too: >> > >> > area :: (Square a b, Numeric b) => a -> b >> > >> > WIth suitable overloads I can call 'area' on any polygon, and I will get >> > the >> > most efficient algorithm for that type of polygon automatically. >> > >> >> I guess I don't understand how this in any way affects what I was >> replying to, which was coalescing assertions on types that were not >> abstract... >> >> but in reality probably just more comfortable/familiar with the keykos >> model of lambda calculus which doesn't assume you'd ever want to give >> out a constructor... > > > My point was you do not want assertions on types, abstract or not.
I don't think we disagree here, I was (at least in my earlier emails) trying to leave open the possibility that an assertion is memoized and inextricably linked to the value, I probably lost this distinction along the way, sorry... > The > assertions belong on the functions, as it is the algorithms that have the > requirements not the data. > > None of this requires you to give out a constructor. In fact we don't know > the type of 'a' the polygon container so we cannot deconstruct it, we use > the abstract interface, which is probably an Iterator. > > The type class "RightTriangle" can be seen as a witness to the proof that > the value passed to the function is a right-triangle. You don't have to do > this proof for every function, as only right-triangles would be a member of > this type-class. > > > Keean. > > > > _______________________________________________ > bitc-dev mailing list > bitc-dev@coyotos.org > http://www.coyotos.org/mailman/listinfo/bitc-dev > _______________________________________________ bitc-dev mailing list bitc-dev@coyotos.org http://www.coyotos.org/mailman/listinfo/bitc-dev
