Hello, Is there a formal specification or standard for the J language? Thank you.
Tarık Özkanlı 8 Şub 2020 Cmt 02:40 tarihinde Marshall Lochbaum <[email protected]> şunu yazdı: > If you're enjoying learning J, I would say it's certainly worth it. Many > of the ideas, like copy or the prefix operator, are incredibly powerful > tools you won't find anywhere else. And learning how these concepts work > in J will help you recognize when to use them in other languages, even > if they can't be written as easily. > > But sometimes another paradigm--Fortran indices, in this case--is more > direct or even more powerful. I think it's important not to obscure or > make excuses for these cases. Doing so prevents us from moving the array > paradigm forward. > > Marshall > > On Fri, Feb 07, 2020 at 04:04:00PM +0100, Rudolf Sykora wrote: > > Dear Marshall and Henry, > > > > > > Marshall Lochbaum <[email protected]> writes: > > > Although a matrix product will execute faster, if I want to write > tensor > > > code that is straightforward, and extends to multiple contracted axes, > I > > > would transpose the contracted axes to the end and combine them with > > > (+/@:*"1). > > > > This is exactly how I was thinking yesterday. But I could not make the > > shapes and ranks fit, and I gave up, and asked the question here, > > thinking that I must have been doing something really wrong... (That the > > problem at hand should be 'easy', especially in J.) > > > > > > > The idea with (|:~ 1 -.~ i.@(#@$)) is to get the list of indices for > > > ... > > > > Thanks for the explanation. When I saw Henry's answer I was taken aback, > > but after some thought I now understand what is going on. > > > > > > > I think this is a weak point for J's array programming style. Just like > > > tacit code works well for small manipulations but gets confusing and > > > difficult as the number of arguments increases, J primitives like rank, > > > transpose, and inner product are excellent for a few axes, but don't > > > work so well when the number of axes increases and the ways they are > > > manipulated become more complicated. In J's defense, most programming > > > languages are pretty awful at this (how many times are you going to > > > write .map before you just give up?). But it's something that bothers > > > me. Sure, I can write a bunch of nested rank operators to do what I > > > want, but why is it so hard to just say which axes correspond to which? > > > > Generally, I wonder whether trying J is worth it. It happened again that > > something one could write explicitly with ease in, say, fortran (the > > code would be more verbose, but straightforward), took me many hours to > > get working in J. I guess, pragmatically, it does not pay off, but, for > > the fun of it, it is interesting to see how far one can get. I love > > those little sniplets that can solve quite complex problems really > > succinctly. > > > > > > Thanks to both of you again, > > Ruda > > ---------------------------------------------------------------------- > > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
