Oh yes, I like this! n is any noun, not just an atom. Henry Rich
> -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Dan Bron > Sent: Monday, October 29, 2007 8:31 PM > To: 'Programming forum' > Subject: RE: [Jprogramming] Inverse of <;.1 > > A synthesis just occurred to me. This is unrelated to the > "more ambitious" proposal I mentioned earlier, but still solves the > problem. > > I wrote (0): > > perhaps the raze of the result of affixing a fill element > > within each box, as in: > > > > <;._1 :. ([: ; ({.~ -@:>:@:#)&.>) > > <;._2 :. ([: ; ({.~ >:@:#)&.>) > > Then elaborated (1): > > Maybe, in line with other uses of !. to specify fill, a > > new fit could be defined, such that: > > > > <;._2!.n ^:_1 <==> [: ; ,&n&.> > > But worried (ibid): > > the phrase suggested above might have to be expressed as > > <;._2^:_1!.n [...] If that's the case, I'm less > > enthused about the idea > > However, we could extend the proposal thus: > > <;._2!.n <==> <;._2@:(,&n) :. ([: ; ,&n&.>) > > (similarly for <;._1!.n and equivalences apply to monads > only. Perhaps initially only for vector arguments.) > > That is, the fit WOULD apply to the nominal verb: it would > specify the fret. It would also apply to the obverse as laid out in > my previous message. > > Advantages: > > (A) Concise. > > (B) Solves a common problem. > (B.i) No worrying about losing the shard. > > (C) Backwards compatible > > (D) Centralized, easily optimized. In particular, in > <;._2 y,n the catenation (and attendant copying > of y ) need not be performed. > > (E) Could easily provide for other optimizations > which would support a large body of extant and > likey future code. In particular, f&.>&.(<;._2!.n) > could be optimized for well-behaved f (the > initial definitionof "well behaved" might be > "doesn't change the type or shape of its > argument") > > For example: > > dtb&.>&.(<;._2!.LF) NB. dtb from lines > > (though this is "poorly behaved" because it > changes the shape of its argument). > > (F) In the spirit of !. > > (G) In the spirit of ^:_1 > > Drawbacks (in addition to those associated with every > backwards-compatible change to the language): > > (A) <;._2 sans fit couldn't have an inverse, or, > if it did, it would be inconsistent with the > definition and inverse of fitted cut. > > (B) Every !. reduces the consistency of J; they > should be used sparingly, if at all. > -Dan > > (0) > http://www.jsoftware.com/pipermail/programming/2007-October/00 > 8564.html > (1) > http://www.jsoftware.com/pipermail/programming/2007-October/00 > 8569.html > > ---------------------------------------------------------------------- > For information about J forums see > http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
