The key function is better described in the Dyalog reference manual, on page 153 here: http://docs.dyalog.com/16.0/Dyalog%20APL%20Language%20Reference%20Guide.pdf
Essentially, it's a grouping function. It's used to create groups of similar things, and apply a function on the individual instances. The examples in the section I referenced above should be pretty clear, I think. Regards, Elias On 3 July 2017 at 00:51, Juergen Sauermann <juergen.sauerm...@t-online.de> wrote: > Hi Elias, > > I am not quite in favour of it and it has problems. > > It is not on my keyboard (even though I am using a Dyalog keyboard). > Not to talk about other keyboards. > > It does not really look like need-to-have function and I suppose it can be > efficiently performed by a short combination of other APL primitives. > > In my opinion adding primitives for every imaginable use case (and > there are certainly use cases for the key function) leads to an overloading > of the APL language in the long run and does not improve the language. > > Another problem is that after reading the description several times, I > still > can't explain in simple terms what the function is actually doing. That > makes it > a good candidate for a never used function if it should ever be > implemented. > > Best Regards, > Jürgen Sauermann > > > > > On 07/02/2017 06:24 PM, Elias Mårtenson wrote: > > How about implementing the key function, ⌸? > > It's described in this article on the Dyalog site: > https://www.dyalog.com/blog/2015/04/exploring-key/ > > Jürgen, are you in favour of this function? > > Regards, > Elias > > >
