Pixie Scheme II:

    Pixie Scheme II is an implementation of the Scheme programming language for the Apple Macintosh™. It runs only on 64-bit Intel Macintoshes using MacOS 10.6 (“Snow Leopard”) or later.  I created Pixie Scheme II as a design prototype for Pixie Scheme III, which runs on the Apple iPad, and which is further described here. Pixie Scheme III has an iPad-like user interface, but it lacks the “R5” procedures that access files (since the iPad hides its underlying Unix file system), and it does not have all of the enhancements beyond “R5”, that Wraith Scheme has.

    Pixie Scheme II was and is an experimental implementation: It is certainly not as well tested or as well documented as Wraith Scheme. I would be delighted to hear what you think of it. If people miss the features that I have taken out, I will probably put them back in a subsequent release.

    Pixie Scheme II is so named because its user interface much resembles the user interface of the original Pixie Scheme of the late 1980s. (For that matter, much of the source code of both Pixie Scheme II and Wraith Scheme is identical to that of the original Pixie Scheme.)

Pixie Scheme II – Overview:

    To run Pixie Scheme II, you need (1) a Macintosh (2) with an Intel processor (3) running at least MacOS 10.6 (Snow Leopard); furthermore, (4) the Intel processor in your Macintosh must be capable of running 64-bit applications. (Snow Leopard only runs on Macintoshes with Intel processors, and any Macintosh with an Intel processor can run Snow Leopard. Unfortunately, some early “Intel Macintoshes” — like my mid-2006 model Macbook 13 — cannot run 64-bit applications, such as Pixie Scheme II. They can, however, run the 32-bit version of Wraith Scheme — Wraith Scheme 1.36 — that is described farther down this page.)

    Pixie Scheme II 1.02 is almost an “R5” Scheme, with “R5” referring to the Revised5 Report on the Algorithmic Language Scheme (1998), edited by Richard Kelsey, William Clinger and Jonathan Rees. That is, this version of Wraith Scheme contains almost all of the required features of R5 Scheme, plus many of the optional ones, plus some enhancements. The “almost” mean that some features required by “R5” are missing from Pixie Scheme II; namely, the procedures that allow access to files: I left them out because Pixie Scheme II is in great part a design prototype for a possible implementation of Scheme for the Apple iPad, and the iPad pretty much hides its underlying Unix file system from users.

    The present release comprises the Pixie Scheme II 1.02 application and a README file. There is a great deal more documentation within the application, accessible via the help menu. Source code for the application is also available, in a separate download, described below.

     The reduced-size screen shot above shows a recent version of Pixie Scheme II shortly after opening. At the top of the pale yellow main window is the “banner” that appears when Pixie Scheme II starts running.

    Pixie Scheme II 1.02 is the third release of Pixie Scheme II; for details, see the “What’s New” section in the Pixie Scheme II Help file.

    Known serious bugs in Pixie Scheme II 1.02: None known at present. If you should find any, by all means send me EMail.