A+ (programming language)


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

History

In 1988, Arthur Whitney began work on the A programming language to replace APL. Other developers at Morgan Stanley extended it to A+, adding a graphical [user interface] and other language features.
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.

Features

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 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.