I think pointing people here: http://www.rogerstokes.free-online.co.uk/31.htm might be good start.
It touches exactly these topics of replacing repeated scalar operations with vector operations. These techniques are applicable in any other language which is able to do vector operations directly (eg. Matlab). I hope this is the next version of the docs in preparation? It seems that the version of Learning J on the jsoftware.com does not contain this chapter (yet). Jan-Pieter 2013/5/19 Linda Alvord <[email protected]>: > I think you missed my point. > > In the vocabulary in "Control Structures" you provide hints to formulate this: > > if. y<0 do. c elseif. y>:0 do. d end. > > A beginner who finds this is likely to assume that this is the best way to > provide a conditional solution in J. > > Sadly, they are likely to work to master the use of this structure. A better > way is not there for them to see. I'm suggesting that a better way (or the > best known option at the current time) be provided right there. > > c*y<0)+(d*y>:0) > > Often these better ways appear on wiki pages. They are only brought to light > by some link on the forum which would otherwise never be found. > > If gems like this one were to appear in the vocabulary section it would > encourage faster development of good writing skills. > > So much of the give and take of the forum reduces concepts to a simpler way > of solving problems. It would be great if those "better ways" could find > their way into the vocabulary. > > Linda > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Roger Hui > Sent: Saturday, May 18, 2013 7:03 PM > To: Programming forum > Subject: Re: [Jprogramming] newbie help: how to avoid division by zero > > We don't do anyone any favors by providin > if. y<0 do. c elseif. y>:0 do. d end. > instead of > c*y<0)+(d*y>:0) > > > For one thing, the former has to work scalar-by-scalar, and for now and for > the forseeable future it'll be orders of magnitude slower that the latter > expression. > >> There are many places where newer and better ways of doing things >> could > be added to save lots of new users many pitfalls. > > Yes, we have newer and better ways of doing things; it's called array > thinking, and booleans returning 0 and 1 instead of false and true, and ... > > > > On Sat, May 18, 2013 at 1:41 PM, Linda Alvord <[email protected]>wrote: > >> try=: 3 : 0 >> c=:12 >> d=:14 >> if. c*y<0 do. c elseif. d*y>:0 do. d end. >> ) >> try _3 >> 12 >> try 0 >> 14 >> try 3 >> 14 >> >> c=:12 >> d=:14 >> y=:_3 >> (c*y<0)+(d*y>:0) >> 12 >> x=:0 >> (c*y<0)+(d*y>:0) >> 12 >> x=:3 >> (c*y<0)+(d*y>:0) >> 12 >> >> Roger, Most people seem to go first to the vocabulary to find a >> starting place to solve their problems. >> >> Wouldn't it be useful to go to "Control Structures" to find a major >> improvement such as the one you just wrote: >> >> if. c*y<0 do. c elseif. d*y>:0 do. d end. >> or: >> (c*y<0)+(d*y>:0) >> >> There are many places where newer and better ways of doing things >> could be added to save lots of new users many pitfalls. >> >> Linda >> > ---------------------------------------------------------------------- > 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
