A+

Paradigm	Array
Designed by	Arthur Whitney
Developer	Morgan Stanley
First appeared	A – 1985; 39 years ago (1985) A+ – 1988; 36 years ago (1988)
Stable release	4.22-1 / March 27, 2008; 16 years ago (2008-03-27)
Typing discipline	Dynamic, strong
License	GNU General Public License
Filename extensions	.., .+, .a, .m[1]
Website	www.aplusdev.org
Major implementations
A+
Influenced by
APL
Influenced
K

A+ is a high-level, interactive, interpreted array programming language designed for numerically intensive applications, especially those found in financial applications.

In 1985, Arthur Whitney created the A programming language^[2] to replace APL.^[3] Other developers at Morgan Stanley extended it to A+, adding a graphical user interface (GUI) and other language features. The GUI A+ was released in 1988.

Arthur Whitney went on to create a proprietary array language named K. Like J, K omits the APL character set. It lacks some of the perceived complexities of A+, such as the existence of statements and two different modes of syntax.

A+ provides an extended set of functions and operators, a graphical user interface with automatic synchronizing of widgets and variables, asynchronous executing of functions associated with variables and events, dynamic loading of user compiled subroutines, and other features. A+ runs on many Unix variants, including Linux. It is free and open source software released under a GNU General Public License. A newer GUI has not yet been ported to all supported platforms.

The A+ language implements the following changes to the APL language:

• an A+ function may have up to nine formal parameters
• A+ code statements are separated by semicolons, so a single statement may be divided into two or more physical lines
• The explicit result of a function or operator is the result of the last statement executed
• A+ implements an object called a dependency, which is a global variable (the dependent variable) and an associated definition that is like a function with no arguments. Values can be explicitly set and referenced in exactly the same ways as for a global variable, but they can also be set through the associated definition.

Interactive A+ development is primarily done in the Xemacs editor, through extensions to the editor. Because A+ code uses the original APL symbols, displaying A+ requires a font with those special characters; a font named kapl is provided on the web site for that purpose.

• Official website^{[dead link]}, aplusdev.org

v t e APL programming
Features	APL syntax and symbols Direct function (dfn) Code pages Iverson bracket Rank Shared Variables
Implementations	Major Dyalog APL APL2 → APLX SHARP APL NARS → NARS2000° Dialects A → A+° APLNext → VisualAPL ELI GNU APL° J° kdb+ K, Q Polymorphic Programming Language (PPL)
Community	Professional associations Association for Computing Machinery: SIGAPL British APL Association Organizations Business Analogic Corporation APL2000 CompuServe Digital Equipment Corporation (DEC) DNA Systems Dyalog Ltd. IBM I. P. Sharp Associates Kx Systems Micro Computer Machines (MCM) Science Research Associates Scientific Time Sharing Corporation (STSC) Soliton Incorporated Telecompute Integrated Systems, Inc. Time Sharing Resources (TSR) Education Carnegie Mellon University (CMU) University of Maryland People Phil Abrams Bob Bernecky Larry Breed Charles Brenner Fred Brooks Jim Brown Adin Falkoff Patrick E. Hagerty Herbert Hellerman Roger Hui Kenneth E. Iverson Dick Lathwell Eugene McDonnell Robert Metzger Roger Moore Alan Perlis John Scholes J. Henri Schueler Bob Smith Edward H. Sussenguth Jr. Arthur Whitney William Yerazunis Rodnay Zaks Iverson Award
Italics = discontinued ° = Open-source software Commons Category