If you'll permit a few comments from a neophyte list-lurker, to my mind right-to-left evaluation has substantial benefits.
An illustrative but trivial example from LISP (Lots of Irritating Single Parentheses?): Take something like (CONS (CAR X) (CDR X)), write it thus: CONS CAR X CDR X ... and evaluate it from _right to left_ using a stack for intermediate values. This works fine without the parentheses. In evaluating from right to left, isn't J often effectively doing something similar --- a fairly natural "Polish notation with evaluation in reverse"? Makes sense to me, anyway (I've played with this idea a bit over the past couple of decades). And is there anyone out there who speaks Arabic? I'd love to hear their take on the left/right vs right/left reading of J. Regards, Jo. On 22 July 2013 13:44, Devon McCormick <[email protected]> wrote: > Understand too that left-to-right evaluation has expressive benefits: in > left-to-right evaluation, -/vec is equivalent to ({.vec)-(+/}.vec) whereas > the default in J gives us alternating sum. Similarly, %/vec is > ({.vec)-(*/}.vec) taken left-to-right but gives us extended fractions. > Take a look at the result of > (+`%)/100$1 or <:(+`%)/100$2 1 to see what nicely falls out of this order > of evaluation. > > > On Sun, Jul 21, 2013 at 9:25 PM, I.T. Daniher <[email protected] > >wrote: > > > I like Raul's style of thinking, comment rescinded. > > > > Best! > > -- > > Ian > > > > On Sun, Jul 21, 2013 at 9:18 PM, Tracy Harms <[email protected]> wrote: > > > > > I > > > On Jul 21, 2013 8:27 AM, "I.T. Daniher" <[email protected]> > wrote: > > > > > > > > You can definitely build similar aliases in J - simply writing 'add > =: > > +' > > > > will get you so far, but the right to left execution order confounds > > > > attempts to make truely human readable sentences, where left-to-right > > > > order is used. > > > > > > > > > > Like Raul, I disagree. I have become fluent enough in J that I > naturally > > > read unfamiliar sentences from left to right, except for the glance to > > the > > > far right that may be needed to qualify whether the sentence as a whole > > is > > > a noun or a verb. Such reading favors general comprehension early on, > > with > > > details filled in as the sentence is completed. > > > > > > As a transition measure, when I've needed to read J sentences from > right > > to > > > left I have, once I understood the sentence, then read it from left to > > > right. Repeated reading of a sentence with various scanning patterns > > builds > > > literacy, I've found. Another example is reading forks from inside, > out, > > as > > > well as from the outside, in. As time goes on you may become less aware > > of, > > > or concerned with, the order in which you read. At least, that's been > my > > > experience. > > > ---------------------------------------------------------------------- > > > For information about J forums see http://www.jsoftware.com/forums.htm > > > > > ---------------------------------------------------------------------- > > For information about J forums see http://www.jsoftware.com/forums.htm > > > > > > -- > Devon McCormick, CFA > ^me^ at acm. > org is my > preferred e-mail > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
