On Wed, Jun 9, 2010 at 3:54 AM, Roger Hui <[email protected]> wrote: > For example: > > foo=: >: > X=: 6 > }.^:(X ~: f...@{.)^:_ ] 3 1 4 1 5 9 > 5 9 > > I think you can omit the second ^: for tiny performance gain: (}.~ X ~: f...@{.)^:_ ] 3 1 4 1 5 9 5 9
> A better solution, I think, is special code for (f i. 1:) > for more general f, similar to the existing special code > for (= i. 1:), (> i. 1:) etc. > > The following timing shows that something different > is going on with (= i. 1:) vs. (x=y)i.1 : > > x=: ?1e6$100 > 6!:2 '1 (= i. 1:) x' > 2.26286e_5 > 6!:2 '(1=x) i. 1' > 0.00541857 > > > > ----- Original Message ----- > From: Alexander Mikhailov <[email protected]> > Date: Tuesday, June 8, 2010 23:22 > Subject: [Jchat] on the J thought style again > To: [email protected] > > > I'm writing a function which goes roughly as the following: > > "from the input array, take first element and do Foo to it. If > > the result is X, stop, otherwise get second element and do Foo > > to it. If the result is X, stop... etc. If the result of last > > element is still not X, return Y" > > > > I started to write like this: > > > > Foo y > > > > and then I realize that I'm doing Foo to all elements of input > > at once, even those which potentially won't be needed. > > > > So, trying to be optimal complicates things. A familiar observation. > > > > What would be an advice to J-ers? Clarity of idea - or, in > > extreme cases, soundness of algorithm? Or, rather, how to find a > > balance here? > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
