Ah, this for multiplying fractions. (And it's different from integer domain/integer valued division <[EMAIL PROTECTED])
* would be different from <[EMAIL PROTECTED] in such cases: 255 * 0.1 0.2 0.8 1 25.5 51 204 255 255 <[EMAIL PROTECTED] 0.1 0.2 0.8 1 25 51 204 255 0.5 * 10 21 33 5 10.5 16.5 0.5 <[EMAIL PROTECTED] 10 21 33 5 10 16 The idea of <.@:* is that we should save on the allocation of the intermediate floating array, and instead store the result in an integer array. The idea of special <[EMAIL PROTECTED] is to speed up the operation in C as compared to evaluating the interpreted conjunction in J. I don't know if the speedup will be significant. If not then it's not worth it. The results that don't into integer magnitude domain should probably conform with usual J rules. I.e. the user is responsible to ensure that the result will stay integer. --- Roger Hui <[EMAIL PROTECTED]> wrote: > How would <[EMAIL PROTECTED] be different from just * ? What > would be the result of the following expression on > a 32-bit machine? > > 1e9 <[EMAIL PROTECTED] 2e9 > > > > ----- Original Message ----- > From: Oleg Kobchenko <[EMAIL PROTECTED]> > Date: Monday, February 5, 2007 11:57 am > Subject: Re: [Jgeneral] large space overhead > > > A simple color space transformation could > > be done by J expressions. For example, > > color/brightness could be as simple as > > > > Y = C*X + B > > > > where C is contracts and B is brightness. > > > > Earlier it was discussed that it would be > > good to optimize integral valued division > > > > <[EMAIL PROTECTED] > > > > But it also makes sense to optimize integral > > valued multiplication > > > > <[EMAIL PROTECTED] > > > > or even maybe integral valued polynomial > > > > <[EMAIL PROTECTED] > > > > For the above example it would be > > > > Y = C*X + B > > > > Y = (B,C) <[EMAIL PROTECTED] X > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > ____________________________________________________________________________________ Do you Yahoo!? Everyone is raving about the all-new Yahoo! Mail beta. http://new.mail.yahoo.com ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
