APL is an acronym for A Programming Language - it is based on a strict (unambiguous) mathematical notation invented by the late Kenneth E Iverson; it is an interpreted, interactive, and array oriented commercial language available for all contemporary platforms. Amongst programming languages, APL has at least three unique/exclusive hallmarks:

1. It is culture 'neutral'; it uses symbols rather than 'reserved' keywords.

2. It is solution 'focussed'; it promotes the expression of algorithms without any consideration of machine architecture or operating system - APL is a type 'inferred' language that rarely necessitates coding structures for loops.

3. It has just one 'simple' operator precedence rule: all expressions evaluate from right to left; if necessary, this default can be overrridden by enclosing parts of an expression in round brackets, with innermost sets of brackets imposing the highest level of precedence.

APL is one of the oldest programming languages, and an important influence on the development of spreadsheets, functional programming[1], Mathematica and MatLab[2]. It is a dynamic, interpreted language based on Iverson's mathematical notation. All data are arrays. Primitive operations all extend to arrays, and are denoted by distinctive graphic symbols rather than words, making APL programs compact and visually striking, with few or no loops.

The language flourishes in scientific, actuarial, statistical and financial applications, and is favored by domain experts writing software for their own purposes. APL is also associated with rapid and lightweight development projects in volatile business environments.

Interpreters are available for a wide range of platforms including PCs, Macs, Linux, mainframes and hand-held computers. Recent Notable extensions to APL interpreters and IDEs include:

• • anonymous lambdas

• • support for class/object programming and .Net assemblies
    

#!wiki comment But this is not a feature of APL as such! It is a matter of implementation. In other words, it should not be mentioned here at all.

Otherwise the two things should not be summarized under one topic: OO and .NET are in this context two different things.

• a version of APL, Visual APL, that is a native language hosted by Visual Studio 2008.

#!wiki comment What exactly is a "native language" in this context? What means "hosted"?

Visual APL is so fundamentally different from others (I dare say: real!) APLs that it needs much more details - or shouldn't be mentioned at all! -- KaiJaeger 2009-07-26 08:04:22

• ActiveX or COM Interrop support allowing APL to use, seamlessly, Windows resources, notably the operating system's Shell, Win32 APIs, and WMI (Windows Management Instrumentation),as well as any COM aware applications, including the MS Office suite.

#!wiki comment Again: this is implementation stuff. The word "seamlessly" is hard to justify in a Wikipedia article anyway. It works when the type declarations delivered by the authors of the COM thing are correct. If not it won't. Often they are not, including some from Microsoft.

• • XML-array conversion primitives
• • support for Subversion and Unicode text handling

#!wiki comment What I am missing is a remark about the most important enhancements: Namespaces in Dyalog and integrated debuggers in some implementation. This is again implementation stuff, but very closely related with the language and it's usage. -- KaiJaeger 2009-07-26 08:04:22

-- StephenTaylor 2009-07-25 05:36:32

[1] http://awards.acm.org/citation.cfm?id=0703524&srt=all&aw=140&ao=AMTURING
[2] http://www.mathworks.com/company/newsletters/news_notes/clevescorner/jan06.pdf