The Return of APL Fingers

I am programming in APL again after a six-year hiatus. My APL fingers are rusty but it’s amazing how deep muscle memory goes. I still know where all the beautiful APL glyphs’ hide on standard keyboards. I’ve programmed in almost a dozen programming languages but I maintain warm feelings for APL because I lost my coding virginity to her.

APL was gentle: abstract, clean, austere and so intoxicatingly elegant. I loved Iverson notation and how it manifested in what remains the most beautiful symbol set ever devised for a programming language. Blinded by passion I overlooked APL’s faults but as my ardor cooled I took notice of one glaring APL problem that persists to this day. Displaying, printing, emailing and now blogging with APL is a pain! Much has improved with the steady adoption of Unicode but even today handling APL imposes burdens. For example, without the APL385 Unicode font your browser will mangle the following APL characters.

!*+-/<=>?\^|~¨¯×÷←↑→↓∆∇∊∘∨∩∪∵∼≠≡≢≤≥⊂⊃⊖⊢⊣⊤⊥⋄⌈⌊

⌶⌷⌹⌻⌽⌿⍀⍂⍇⍈⍉⍋⍎⍐⍒⍕⍗⍙⍝⍞⍟⍡⍢⍣⍤⍥⍨⍪⍫⍬⍱⍲⍳⍴⍵⍷⍸⍺⎕◊○

By the way, if you have not installed APL385 Unicode I highly recommend downloading and installing it. Regrettably installing a Unicode APL font will not fix all your APL character problems! In particular you cannot reliably:

1. Copy and paste APL code between APL vendors or between APL and other languages.
2. Typeset APL listings with ubiquitous LaTeX packages like lstlisting.
3. Post APL idioms on Twitter. Twitter’s 140 character limit is not such a big deal for APL.
4. Print on arbitrary network printers! It’s the 21^st century yet office printers are routinely limited by parochial IT policies to a small set of standard fonts.

APL’ers  almost relish these irritants after all problem solving is what APL’ers do! We don’t go crying to momma; we squash whatever is annoying us and get on with deeper problems.

Currently I am dealing with how to display APL functions on WordPress. WordPress supports a source code highlighting plug-in based on Alex Gorbatchev’s excellent JavaScript SyntaxHighlighter. The WordPress plug-in produces wonderful results for well known languages like C# and by defining language specific JavaScript classes you can highlight languages like APL. Eric Lescasse has done this for APL+WIN code so it is possible, (given Unicode APL fonts), to render highlighted web friendly APL code. Unfortunately WordPress does not support APL highlighting, (what a surprise), and has banned user JavaScript classes on their freebie blogs. Apparently some programmers abuse JavaScript, (another surprise), and uncontrolled JavaScript’ing might endanger the WordPress business model.

This leaves the users of peculiar programming languages with a problem. We can pester WordPress to support new languages or we can roll our own. I am starting a campaign to get APL and J on WordPress’s list of highlighted languages and while I am waiting for official support I will roll my own. Fortunately, highlighting code for blogs is not difficult. The much maligned MS Word (2007 and beyond) can crank out blog happy APL provided you have UTF-8 APL Unicode text to format. Getting UTF-8’ed APL is the tricky bit. Some APL systems like Dyalog directly support UTF-8 and others are planning to do so. APL+WIN cannot spit out UTF-8 but it’s not difficult to transform APL+WIN to UTF-8. The APL Wiki contains some slick APL+WIN functions to convert internal APL text to and from UTF-8.

To get a sense of why all this fuss is worthwhile consider the following APL function taken from Eugene McDonnell’s superb essay Life: Nasty, Brutish, and Short.

∇ z ← LifeKnuth w;v
v ← w
w ← w + (1 ⌽ w) + ¯1 ⌽ w
w ← w + (1 ⊖ w) + ¯1 ⊖ w
w ← w + w – v
z ← w ∊ 5 6 7
∇

This little function is not the shortest APL Life function but in my opinion it’s the clearest and most concise description of Life’s generation rules out there. Tool of thought is not an empty APL marketing slogan. It’s the real deal!