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| Paradigm | array |
|---|---|
| Appeared in | 1988 |
| Designed by | Arthur Whitney |
| Developer | Morgan Stanley |
| Typing discipline | dynamic, strong |
| Major implementations | A+ |
| Influenced by | APL |
| Influenced | K |
A+ is an array programming language, a dialect of APL with aggressive extensions. Arthur Whitney developed the "A" portion of A+, while other developers at Morgan Stanley extended it, adding a graphical user interface and other language features. A+ was designed for numerically intensive applications, especially those found in financial applications. A+ runs on many Unix variants, including Linux. A+ is a high-level, interactive, interpreted language.
A+ provides an extended set of functions and operators, a graphical user interface with a wide selection of widgets, automatic synchronization of widgets and variables, asynchronous execution of functions associated with variables and events, dynamic loading of user compiled subroutines, and other features. A newer graphical user interface 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 broken up 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 called "kapl" is provided on the web site for that purpose.
Arthur Whitney went on to create the K programming language, a proprietary array language. Like the J programming language, K dispenses with the APL character set. It does not have some of the perceived complexities of A+, such as the existence of statements and two different modes of syntax.
A+ is licensed under the GNU General Public License.
External links
- A+ Development.org A+ is freely available under the GNU General Public License
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