24 May
2005
24 May
'05
6:44 a.m.
On Mon, May 23, 2005 at 07:24:50PM +0200, Benjamin Franksen wrote:
On Monday 23 May 2005 17:35, Ross Paterson wrote:
foldr_l :: (a -> b -> b) -> b -> Seq a -> b foldr_l f z xs = case viewL xs of EmptyL -> z x :< xs' -> x `f` foldr_l f z xs'
The current definition is equivalent to [this] (but operates directly on the internal structure).
I wonder: Can a compiler optimize the above so that it is as efficient as the 'real' version? If not, why? If yes, everybody could easily create their own folds.
No, they're too different in structure for a compiler to work out the transformation. People can still create their own folds -- they just lose a constant factor over the insiders.