APL Wiki
Learning APL
Note to contributors: Additions and corrections to this tutorial are welcome. Please keep in mind that it tries to be vendor neutral : where possible examples should work in any version of APL. Please make it clear when code is specific to a particular interpreter. |
This tutorial aims to teach some of the basics of the APL language.
It is adapted from an original version written to accompany MicroAPL's APLX interpreter which is available in PDF form.
The present version has been slightly modified so that examples should work with a number of APLs, including:
Dialect |
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APLX from MicroAPL |
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Dyalog APL 1 |
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APL2 from IBM |
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APL+Win from APL2000 2 |
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VisualAPL from APL2000 2 |
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1 Note that with a default installation, some of the examples won't work with Dyalog: Dyalog offers the system variable ⎕ML which can be set to various values. With ⎕ML←3 all examples will work. See DyalogMigrationLevels for details.
2 Core APL statements illustrated in this tutorial can be executed in VisualAPL from APL2000, however VisualAPL fundamentally extends APL to be inherently based on Microsoft .Net and requires Visual Studio 2008. Therefore it is recommended that the http://forum.apl2000.com/viewtopic.php?t=325 tutorial specific to VisualAPL be used.
The core APL language is similar in all these products, although each vendor has added proprietory extensions. Where code is specific to a particular APL interpreter it will usually be indicated in the text.
Once you're familiar with the material covered here, you might also want to check out Further Topics in APL which covers some more advanced topics.
Trying APL
The APL tutorial will be most effective if you actually try the example code in an APL interpreter. Several vendors provide free or low cost evaluation licenses:
To download a time-limited evaluation copy of APLX for Windows, Macintosh or Linux, visit MicroAPL's Download page. You can also download an older Linux version which is free for personal use.
To apply for a free educational license, or a cheap (£50/€75) non-commercial copy of Dyalog APL visit Dyalog's Download zone
NARS2000, an Open Source APL, does not compete against the commercially available APL implementations, but it is a fully-fledged APL implementation. Apart from the last chapter (15) you can do everything mentioned in this tutorial with NARS2000.
APL2000 and IBM offer their respective interpreters 'free' to educational establishments - contact them via their web site.
A no-cost, demonstration and evaluation copy of Visual APL is available for Visual Studio 2008 users - see www.apl2000.com.
The Finn APL Idiom library (for first generation APL) and IBM's APL2 Phrases (for second generation APL) are useful references for students and professionals alike.
Installing the APL font
To display the material in this tutorial properly, you need to ensure that
- your browser can correctly handle Unicode (UTF-8) encoding
you have a suitable APL Unicode font installed on your system. Note that non-Unicode APL fonts like "Dyalog Std" or "Causeway" won't work!
Most modern Browsers (such as Internet Explorer 6 or later, Firefox v2 or later, Safari v3 or later) should be fine. However, we have found problems using Firefox v2 on the Macintosh (the Windows version is OK, and Firefox v3 on the Macintosh is OK).
APL code on this Wiki is encoded using Unicode UTF-8. It should display correctly provided you have at least one of these APL fonts installed on your system:
Adrian Smith's APL385 Unicode font (http://www.vector.org.uk/resource/apl385.ttf)
MicroAPL's APLX Upright Unicode font (http://www.microapl.co.uk/download/aplx_unicode.ttf). If you have installed a desktop version of APLX (full or evaluation copy), you will have this font installed already.
- IBM's "Courier APL2" font which comes with APL2.
- Phil Chastney's "SiMPL" font.
Phil Chastney's "SiMPL medium" font which can be downloaded from the AplCharacters page. NARS2000 is using this font.
The fonts are listed in the order in which the APL wiki tries to make use of them. Of course this has an impact only if you have installed more than one font.
If you don't have either of these fonts installed, the Wiki's style sheets are set to fall back on Microsoft's Arial font. Some versions of this font (e.g. the "Arial Unicode MS" version which ships with the international support component of MS Office) do have the APL characters, but it is not a monospaced font. This means that code samples will display the correct characters, but may not be aligned correctly.
If you do not have either of the APL fonts listed nor a suitable version of Microsoft's Arial font, APL characters will not display properly.
Here's a sample of text which should display in the APL font:
X ← 3 3⍴÷⍳9 ⋄ Y ← DATA[⍋DATA] ⍝ A comment
It should appear in your browser something like this:
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(this is a picture, not text; it will always display APL chars)
If it looks more like this then you do not have an appropriate APL font installed:
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