Understanding-j: An introduction to the J programming language that gets to the

Summary

J versions: 9.4.2, Found anything wrong? File an issue at https://github.com/bugsbugsbux/understanding-j/issues. Understanding J An introduction to the J programming language that gets to the point. It is intended for those with (some) programming experience, but others should be mostly fine after looking up some basic programming terms like function, argument, class, instance, inheritance, statement, expression, etc. Don't treat this as a reference: Section titles do not introduce an exhaustive explanation of a certain topic, but serve to give this document a rough structure. Individual sections are not intended to be read in isolation from the others and assume the knowledge of previous sections. Run the examples and read the comments! If you have J installed you can open this file in JQt via the file-selection dialog which opens with ctrl+o (make sure to set the filetype-filter to "all"). Click on a line with J code and press ctrl+enter to execute it. Covered builtins are listed in the appendix with a short description. Important links: Project Homepage: https://jsoftware.com Online J interpreter: https://jsoftware.github.io/j-playground/bin/html2/ All builtin operators , with links to their wiki pages: https://code.jsoftware.com/wiki/NuVoc , with links to their wiki pages: https://code.jsoftware.com/wiki/NuVoc Good old wiki: https://www.jsoftware.com/help/dictionary/contents.htm Cheatsheet/Reference Card (not for beginners): https://code.jsoftware.com/wiki/File:B.A4.pdf J was first released in 1990 as a successor to APL, an alternative mathematical notation that is computer-executable and works well with multi-dimensional array data. Most notably J switches from APL's custom symbol-set to ASCII only, calling most basic builtins by a single symbol or a symbol with appended dot or colon, and giving distinct meaning to single symbols that usually appear in pairs like various braces and quotes ( []"{} etc). : NB. comments the rest of the line (latin: nota bene). J h...