What is it?

A set of durable keycap stickers for your keyboard to ease programming in APL.

APL (A Programming Language -- really, that's what it stands for!) is an array-based programming language; in fact, it's the granddaddy of array-based languages (including, but not limited to: A+, J, K, Q, BQN, ...). It is a mathematics-oriented language, arising from the notation invented by Kenneth E. Iverson.

APL is an amazingly powerful language and will change the way you think about programming. Array-based languages are quite different from other so-called 'modern' programming languages. It pioneered the concepts of map/reduce and arguably the entire field of numeric computing itself. Modern statistical and numeric frameworks like Python's NumPy, the MATLAB language (and even spreadsheets!) can trace their roots to APL (see Iverson Ghosts).

Why did you make it?

Since APL uses an extended symbol set which is not present on any retail keyboard, one must always have an APL keyboard chart somewhere, either physically as a reference card or in a background window on the desktop which isn't always visible. It can be a bit of a barrier to new users getting comfortable with the language.

APL has many modern implementations: some commercial, some free. I am particularly fond of GNU APL (Hint: get the latest SVN version rather than the older v1.8 there and build it to suit your system).

This keyboard layout will also work just fine with other modern commercial implementations, such as Dyalog APL and NARS2000.

What makes it special?

These keyboard cap stickers, made of durable PVC and professionally-printed, are easily applied onto standard laptop or PC desktop keyboards. Dedicated replacement keycaps or entire keyboards invariably cost many times this, reaching into the hundreds of dollars (and no one it seems makes replacement keycaps for laptops).

They can easily be replaced or removed without damaging your keyboard's original silkscreening.

For guides on setting up your Linux or Windows keyboard to input APL see my blog post here or the APL wiki page or here.

What if I have an non-US Keyboard? Do you plan to do UK, FR, DE, ... layouts?

For now, I only have the US layout. To see if these can be easily used on your keyboard layout, consult the Dyalog APL keymap diagrams for various countries here.

With a bit of scissor handiwork, it looks like the UK layout shouldn't be too hard to do (the quote (") and at (@) symbols can be snipped out, leaving your keyboard's originals and the pound visible). Other layouts might take more work. But if you need an international layout, Please contact me! If I get enough demand for different country layouts, I may be able to produce them!

NOTE There is one minor print error -- the APL statement separator (⋄ 'diamond') and quad-diamond (⌺) glyphs are stacked incorrectly on the tilde key sticker. Oops. :P If it bothers you horribly, just cut this sticker in half and flip the right part upside-down before applying.

For a great introduction to APL, see APL2 At A Glance.

IF A STICKER LOOSENS...

Not to worry! If the key stickers' adhesion ever does come loose:

1. Take off the loose sticker and carefully peel or wipe off the original glue (usually it peels off as a single clear piece);

2. Carefully, gently scrub off both the keyboard key and the back of the removed APL key sticker with a microfiber cloth wetted with isopropyl alcohol to remove any gunk, and let dry;

3. Rub the now-cleaned APL key sticker with a paste-glue stick (I have found that Elmer's All Purpose Glue Stick works great). Not too much, not too little paste :)

4. Replace sticker on keyboard. Press gently but firmly, rubbing from corner to corner with your fingernail or the bottom of a small spoon (nothing sharp) across all of it to ensure a good bond. Let dry for an hour.

I have had two keys slip due to heavy use over the past year and a half (the D and F since they get heavy use being in the home row, I suppose). After treating with the above, they haven't budged again!

Update: A previous buyer, who really knows his glues, has informed me that Canopy Glue (Formula 560) from Zap is even better! Clean both surfaces (keycap and back of APL sticker) with alcohol, let that evaporate, then apply glue to one surface and allow to dry for a few minutes.