A more general phrase is proposition # ] Whether it merits support by special code is another matter.
----- Original Message ----- From: Dan Bron <[EMAIL PROTECTED]> Date: Monday, November 5, 2007 7:08 Subject: [Jprogramming] Performance of retain/expunge To: Programming forum <[email protected]> > I observe the perfomance difference: > > > x0 =: #~ e.&'ABCDEFGHIJKLMNOPQRSTUVWXYZ' > > x1 =: -.&(a.-.'ABCDEFGHIJKLMNOPQRSTUVWXYZ') > > > M =: 4e6$a. > > (x0 > -: x1) M > 1 > > > ts =: 6!:2 , 7!:2@:] > > %/ > 100 ts&> x0`x1 ,L:0 ' M' > 3.80106 1.12498 > > The difference is even more pronounced with integers: > > > w =: 20?100 > xi0 > =: #~ e.&w > xi1 > =: -.&((i.100)-.w) > > > N =: ?1e6$100 > > > (xi0 -: xi1) N > 1 > > %/ 100 ts&> xi0`xi1 ,L:0 ' N' > 7.4249 0.500099 > > I think the first form is the clear, obvious way to code this > verb. It's also more general, in the case where we know > only the identities of items we want to retain, not the whole > universe. > Could it be supported by special code (e.g. by avoiding the > intermediate boolean array)? ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
