Tacitly, diffadv =: (}. - }:) ^:
> My guess, interpreting the verb-making form, is that ] > denotes values that differ on each cycle. If this is > accurate, I've learned something about power. > I don't think you have this right, but I'm not clear about what you're saying. Henry Rich > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Tracy Harms > Sent: Thursday, December 13, 2007 2:55 PM > To: [email protected] > Subject: [Jprogramming] forward differences > > Thank you, Messrs. Rich, Boss, Miller and McCormick > for the helpful replies. > > I can add to the list of solutions the following: > > diffadv=: 1 :'(}. - }:)^:u' > 2 diffadv (i.10)^5 > 30 180 570 1320 2550 4380 6930 10320 > > Although I don't know how to refer to them, I find two > very different contexts in J composition. One is where > verbs are *used*, the other is where verbs are > *formed.* Examples of each, here: > > list=: (i.10)^5 > order=: 3 NB. i.e. third-order > > ]noun=: (}. - }:)^:order list > 150 390 750 1230 1830 2550 3390 > > ]verb=: (}. - }:)@]^:[ > ] (}. - }:)@]^:[ > order verb list > 150 390 750 1230 1830 2550 3390 > > I do not yet properly grasp why the two nouns that > come into play must be reorganized between these two > modes. To demonstrate that they must, this is what > happens when we try to use the verb-forming > construction for immediate calculation: > > ]noun=: (}. - }:)@list^:order > |domain error > | ]noun=: (}.-}:)@list^:order > > Not that this would look right to me in the absence of > an error message, for the diff function (}. - }:) > needs to be processing distinct data on each pass, and > this seems to specify that the same data should be > bound each time. > > My guess, interpreting the verb-making form, is that ] > denotes values that differ on each cycle. If this is > accurate, I've learned something about power. > > What still eludes me, though, is a naturalness in > reading, such that I anticipate this reversal of > power-specification and data when moving from full > calculation to tacit definition. > > At this point, however, I have several engaging > variations in hand for study. Thanks, again. > > > Tracy > > > > ______________________________________________________________ > ______________________ > Looking for last minute shopping deals? > Find them fast with Yahoo! Search. > http://tools.search.yahoo.com/newsearch/category.php?category=shopping > ---------------------------------------------------------------------- > For information about J forums see > http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
