14 Jan
2013
14 Jan
'13
2:47 p.m.
Somebody claiming to be Simon Peyton-Jones wrote:
* For x1 we can write map MkAge x1 :: [Age]. But this does not follow the newtype cost model: there will be runtime overhead from executing the map at runtime, and sharing will be lost too. Could GHC optimise the map somehow?
My friend pointed out something interesting: If GHC can know that MkAge is just id (in terms of code, not in terms of type), which seems possible, and if the only interesting case is a Functor, which seems possible, then a RULE fmap id = id would solve this. No? -- Stephen Paul Weber, @singpolyma See http://singpolyma.net for how I prefer to be contacted edition right joseph