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An Implementation of A+

A+ is best described as a reduced instruction set APL. It was designed and developed by Arthur Whitney around 10 years ago as a super-fast engine for manipulating timeseries data. It was subsequently developed as A+ by Morgan Stanley and has now been placed into the public domain under the GNU public licence. This full version includes X-window support and runs under various flavours of Unix and is available from along with full source code.

The A+ Project at the British APL Association

In spring of 2001 it was agreed to allocate funds to investigate an implementation of the core A+ interpreter under Windows 9x and 2000. This phase of the investigation is now complete, and the interpreter is available for download from these pages. Please feel free to try it out, but be aware that the environment is totally primitive and that you will have to be a little persistent to achieve more than '2+2' in console mode. You might like to start with some of the simple scripts on the Getting Started pages, which include a translation into A+ of some functions from Norman Thomson's excellent “APL for the Maths Classroom”. Any components with Unix dependencies (such as the .sys context) are not available in this version.

This site reproduces a subset of Morgan Stanley's original A+ documentation (available in full at, with acknowledgement of copyright where appropriate. Some sections (relevant only in a Unix environment) have been pruned. You will need the KAPL TrueType font installed to read the sample code in your browser. This entire site content is available as a ZIP file from the downloads page if you would like to read it offline.

Adrian Smith
Chairman, British APL Association

© British APL Association 2001
Please send any comments to Adrian Smith via - thank you.