16 Feb
2009
16 Feb
'09
9:08 a.m.
Am Montag, 16. Februar 2009 14:21 schrieben Sie:
Aha! Wolfgang is a man who knows his own code :) Yes, I've seen this a couple of times but when I saw it again in Grapefruit, I wanted to know how this usage of existentials worked, since I'm sooo curious to find out how you managed to use the type system for solving some of the typical FRP problems.
Note that in Grapefruit I not only use rank-2 polymorphism (corresponding to existentials) but also impredicative polymorphism, namely in FRP.Grapefruit.Signal.switch. However, the idea behind using impredicativity here is the same as the reason for using rank-2 in Control.Monad.ST.runST, FRP.Grapefruit.Circuit.create and Graphics.UI.Grapefruit.Circuit.run. Best wishes, Wolfgang