Actually my first steps into APL were teasered by april[1], a Common Lisp library introducing an APL-like dialect as a domain specific language (like f.e. regular expressions). I was highly impressed by all the funny symbols, f.e.: ⎕← 5 5 ⍴ ⍳ 25.
As my appetite was wheted, I made my first hands-on-experience with APL in the 2020 AOC challenge[2].
As I read "_A_ _P_rogramming _L_anguage" by Kenneth IVerson[3] and the story behind of it, I finally fall in love with APL as a tool of thought. So I started learning APL - at first the ancient APL(1), especially through "APL - An Interactive approach" by Gilman[4]. As my first APL of choice was GNU-APL[5] - which mimics actually APL2 - I proceeded with "APL at a Glance"[4].
APL-dialects are programming languages, where you do more thinking than typing.
Russtopia has a great capsule on APL, especially a big collection of papers and books.
If you are interested in a todays modern APL, either check out Dyalog APL (commercial), or the "offical" 2nd APL named J[6] by Kenneth Iverson (for about 10 years open source).
For actually doing professional stuff and daily work, J is my todays choice. I am missing the funny symbols ;), but the eco-system, libraries, addons and community are much more state of the art, and it is open source, compared to Dyalog APL. Also the array model (flat with boxes) and tacit-style, if you get around it, are great.
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