In the places I go, there are things that I see

That I never could spell if I stopped with the Z.

I'm telling you this ’cause you're one of my friends.

My alphabet starts where your alphabet ends.

                                                                -- Doctor Seuss

    This page describes and provides shareware and freeware I have released. There are five items, each described in more detail farther down the page:

        Shareware:

                Wraith Scheme 2.00 (64-bit application) -- released 22 September 2009.

                Wraith Scheme 1.36 (32-bit application) -- released 17 November 2009.

                Percival 1.00 -- released 8 February 2007.

                Pixie Scheme -- released January, 1991. No typo, I really do mean 1991.

        Freeware:

                Red Sky 1.21 -- released 14 October, 2007.

    Note:  There is a bug in Wraith Scheme 2.00 that does not occur on all Macintoshes. I have a fix -- Wraith Scheme 2.01 beta -- for those of you who need it. That fix is described further down the page.

    Wraith Scheme, Percival, and Red Sky are Apple Macintosh™ applications for current Macintoshes.  Wraith Scheme 2.00 runs only on Intel-based Macintosh computers that have processors capable of running 64-bit programs. Wraith Scheme 1.36, Percival, and Red Sky are universal binary; they run on both Intel-based and PowerPC-based Macintosh computers. Pixie Scheme is a Macintosh application that is probably of interest only to collectors of extremely old Macintoshes. Each program is described in more detail below.

    Source code for the 64-bit version of Wraith Scheme is available for redistribution under the GNU General Public License.  Details are provided below.

    “Shareware” can mean many things: To me, it means public service. These applications are fully functional as downloaded -- no activation codes, nothing to buy, and no pop-up reminders to send me a shareware donation. (Donations are welcome, if you want to make one.)  Any lack of functionality is likely due to inadequate pre-release testing by me: Send in a bug report so I can get busy fixing it.

    If you need assistance with any of this software, or if you have a complaint, an enhancement request, or a bug report, or if you are simply curious about how something works, then by all means let me hear from you. My EMail address is Jay_Reynolds_Freeman@mac.com.

Wraith Scheme (64-bit application):

    There is a bug in Wraith Scheme 2.00 that does not occur in all Macintoshes.  The bug is that while typing input to Wraith Scheme, the area where you type occasionally scrolls so that it shows the last line that you typed previously, instead of the line you are actually working on. If you have that problem, download Wraith Scheme 2.01 beta by clicking this link: Wraith Scheme 2.01 beta.dmg. This bug did not occur on any of the three Macintoshes I own, so I had no idea it was present until someone told me about it. I apologize profusely, but at least that gives me another irrefutable excuse to buy more computers. Wraith Scheme 2.01 beta is identical to Wraith Scheme 2.00 except for a three-line source code change that is reported to have fixed the problem.

    To run Wraith Scheme 2.00 or 2.01 beta, 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 of the early “Intel Macintoshes” — like my mid-2006 model Macbook 13 — cannot run 64-bit applications. They can, however, run the 32-bit version of Wraith Scheme described farther down this page.

    This release is 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 all of the required features of R5 Scheme, plus many of the optional ones, plus some enhancements. The most noticeable enhancement is for parallel processing, and is described in more detail a few paragraphs down.

    The present release comprises the Wraith Scheme 2.00 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 Wraith Scheme shortly after opening. At the top of the pale yellow main window is the “banner” that appears when Wraith Scheme starts running. The extra panel — Apple calls it a “drawer” — at the side of the main window has buttons for the most important Wraith Scheme commands. The drawer at the bottom is an instrument panel that shows what Wraith Scheme is doing and how some of its internal parameters are set. The square colored areas at the right side of this panel emulate the flashing status lights that were common on early computers.

    Wraith Scheme has major enhancements for parallel processing, by which I mean many separate Wraith Scheme processes running at the same time, sharing Scheme memory. One privileged process — the “MomCat” — supervises a handful of less privileged processes —  “kittens”. There are low-level primitives for interprocess communication and for locking shared data structures. Below is a reduced-size screen shot showing several parallel Wraith Scheme processes, each with its own separate and differently-colored window and with its own separate and differently-colored icon.

For a link to the portion of the web-browsable Wraith Scheme Help file that discusses parallel processing, click this link: Wraith Scheme parallel processing.

    Wraith Scheme has a history: In the late 1980s, I developed an implementation of Scheme that ran on early versions of the Apple Macintosh. It was called “Pixie Scheme”, was available as shareware, and actually saw modest use here and there. An Internet search for it will turn up a few links. I shelved the Pixie Scheme project in 1991, but in 2006 and 2007 I dusted it off and got an upgraded version to run in a Unix shell (a window of the “Terminal” application) on my new Macbook. Then I built a full Macintosh application around the heart of the code for the Unix-shell implementation. The changes seemed big enough to warrant a new name: Wraith Scheme.

    Wraith Scheme 1.00 was pretty much a straight port of Pixie Scheme, and was not quite an “R4” Scheme. Wraith scheme 1.10 was R4, 1.20 was R5, and 1.30 added support for parallel processing. Interim versions were bug-fixers or modest enhancements, or both.

    Wraith and Pixie were much-loved pet cats, now deceased. The icons for these two programs are stylized representations of what they looked like.

    I wrote Pixie Scheme and Wraith Scheme mainly because I wanted a Scheme implementation whose workings I knew well enough so that I could go in and mess with it to suit myself. My motivation for wrapping these programs up as shareware releases was about equal parts the fun of addressing the technical challenges of doing so, the desire to perform a public service, and the wish to see who might find them useful or interesting.

    Wraith Scheme 2.00 is the first release of Wraith Scheme as a 64-bit application; for details, see the “What’s New” section in Wraith Scheme’s help file.

    Known serious bugs in Wraith Scheme 2.00: See the discussion of Wraith Scheme 2.01 beta above for a bug that affects Wraith Scheme 2.00 on some, but not all, Macintoshes . If you should find any more bugs, by all means send me EMail.

Wraith Scheme (64-bit) Source Distribution:

    Wraith Scheme 2.00 is available for redistribution under the GNU General Public License.  I suggest you read the Distribution Notes before downloading it.

    To obtain the distribution as a Macintosh disk image, click this link: Wraith Scheme 2.00 Source Distribution.dmg. The disk image will probably only be useful to Macintosh users; mouse it to open it.

    To obtain the distribution as a tar file, click this link: WraithScheme.64.tar.gz.  Untar the tar file with the Unix or Terminal shell command: “tar -xzf WraithScheme.64.tar.gz”.

    After untarring the tar file or opening the disk image, you will find a single directory or folder, “WraithScheme.64”, with many subdirectories, and with a copy of the distribution notes at top-level inside it. The distribution contains a great deal of documentation, including a copy of the HTML file “Wraith Scheme Internals.html”, which is intended to help you work with and understand the software distribution. See the distribution notes for how to locate that file within the distribution. A web-browsable copy of that file is available here: Wraith Scheme Internals.

    I have never released a piece of software as open source before; please bear with me. Let me know if you have any problems getting or using the distribution. I will keep a running commentary of simple issues or matters of interest that have to do with the source distribution here: Release Commentary. At the moment, the last entry in the Release Commentary was made on 13 November, 2009.

    Known serious problems with the Wraith Scheme 64-bit source distribution: None known at present. If you should find any, by all means send me EMail.

    As described above, I have released a bug-fixer, Wraith Scheme 2.01 beta, to fix a problem that occurs on some Macintoshes.  The source code change comprises three lines in one of the Wraith Scheme 2.00 source files, and is described in the README file that accompanies Wraith Scheme 2.01 beta.

Wraith Scheme (32-bit application):

    To run Wraith Scheme 1.36 you need a Macintosh that is running at least Mac OS 10.4 (Tiger).  Wraith Scheme 1.36 should run equally well on Macintoshes with Intel processors and Macintoshes with PowerPC processors. If you have a newer Macintosh, running Snow Leopard, you might also be able to run the newer, 64-bit version of Wraith Scheme. Scroll up this page to learn more about it.

    I expect to keep a 32-bit, universal binary version of Wraith Scheme available as long as there is any demand for it. That version will probably not have such new features as I introduce into the 64-bit version, but I expect to fix any major bugs that turn up.

    This release is 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 all of the required features of R5 Scheme, plus many of the optional ones, plus some enhancements. The most noticeable enhancement is for parallel processing, and is described in more detail a few paragraphs down.

    The present release comprises the Wraith Scheme 1.36 application and a README file. There is a great deal more documentation within the application, accessible via the help menu. There is no source code for the application itself, but the 64-bit version has been released open-source, as described earlier herein.

     The reduced-size screen shot above shows a recent version of Wraith Scheme shortly after opening, running a Scheme procedure. At the top of the pale yellow main window is the “banner” that appears when Wraith Scheme starts running. Below that is a record of a few short interactions with Wraith Scheme; the text shows what the user entered and how Wraith Scheme responded. The user has just typed the line “(increment 42)”, visible near the bottom of the main window, but has not yet pressed “return” to make Wraith Scheme process it.

    Wraith Scheme has major enhancements for parallel processing, by which I mean many separate Wraith Scheme processes running at the same time, sharing Scheme memory. One privileged process — the “MomCat” — supervises a handful of less privileged processes —  “kittens”. There are low-level primitives for interprocess communication and for locking shared data structures. Below is a reduced-size screen shot showing several parallel Wraith Scheme processes, each with its own separate and differently-colored window and with its own separate and differently-colored icon.

For a link to the portion of the web-browsable Wraith Scheme Help file that discusses parallel processing, click this link: Wraith Scheme parallel processing.

    Wraith Scheme has a history. If you would like to learn about it, that history is described in a little more detail earlier in this page, in the description of the 64-bit version of Wraith Scheme.

   Wraith Scheme 1.36 is a bug-fixer for the previous release; for details, see the “What’s New” section in Wraith Scheme’s help file.

    Known serious bugs in Wraith Scheme 1.36: None known at present. If you should find any, by all means send me EMail.

Percival:

Percival is a stand-alone shareware application for Macintoshes using OS X 10.4 or later. Percival is universal binary -- it will run on both newer Macintoshes that use Intel processors, and on earlier units that use PowerPC processors.

    The name, “Percival”, provides an acronym for what the application is: Pixel Editor for the Repair and Customization of Icons, when Vector Applications Lose. I wrote Percival because I needed a pixel-level image editor for touching up icons, and installed only those features that were useful to me. I will probably not release any newer versions of Percival unless I find major bugs or discover that I need more editing capability.

    The release comprises the Percival application, a README file, and a copy of the Percival Help file. There is no source code for the application itself.

    The reduced-size screen shot above shows Percival editing the image for its own icon. The big image that fills most of the window is the workspace where the user makes changes. The smaller versions at left show the current image at several sizes, so the user can see what it will look like when Mac OS changes its size.

    Percival, like Wraith and Pixie, was a much-loved pet cat. That’s his picture in the icon.

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

Pixie Scheme:

    The release comprises the Pixie Scheme application, some text files, and a folder with a few short samples of Scheme code. There is a help file — well, sort of: It’s a HyperCard™ stack. (I miss HyperCard.)  There is no source code for the application itself. Pixie Scheme is shareware.

    I do not have a screen shot for Pixie Scheme. The icon is a tolerable stylized representation of what cat Pixie actually looked like.

    I decided to make this venerable distribution available because I have read that there are people who collect and use old Macintoshes: Appropriate software must be scarce and difficult to locate. I myself no longer have any old Macintosh hardware or software, so there will probably be no further releases of Pixie Scheme.

    Known serious bugs in Pixie Scheme:  None known at present. And I regret to say, that if there are any, there is almost certainly nothing that I can do to fix them.

Red Sky:

Red Sky is a stand-alone freeware application for Macintoshes using OS X 10.4 or later. Red Sky is universal binary -- it will run on both newer Macintoshes that use Intel processors, and on earlier units that use PowerPC processors.

    Red Sky floats a nearly-opaque window of variable opacity on top of the main Macintosh display. The window has a small area that is less opaque, whose opacity is also variable, centered on the position of the cursor. The effect is as if you were using a well-shielded flashlight to illuminate your desktop, with the center of the flashlight beam tracking the mouse. The flashlight beam is off entirely when the cursor is in motion, but reappears once it is stationary again. The intent is that amateur astronomers may use their Macintoshes at night, in the field, while observing, with reduced adverse effect on their night vision. The floating window passes typing and mouse operations through to whatever is underneath, so you can use other applications while Red Sky is running. The name “Red Sky” is based on the old adage, “Red sky at night, sailors’ delight …”.  Make that “amateur astronomers”, and I hope it will be equally appropriate.

    Yet there is an unfortunate truth: Current Macintosh displays really aren’t suited for use with fully dark-adapted eyes. Even with the display as dark as Red Sky can make it, and the Macintosh hardware setting for display brightness at the lowest setting short of turning it off completely, the grayish background  glow from the screen may be too much for use at what amateur astronomers call a “dark-sky location”: When I use my 2006-model 13-inch Macbook at such a site, the glow bothers me. If you agree, you will probably need to use a piece of red transparent plastic over the display. Red Sky might be useful for fine adjustments of brightness in that case.

    The release comprises just the Red Sky application and a “README” file. There is no source code for the application itself.

    The reduced-size screen shot above shows Red Sky in use on my own desktop. Note the “center of the flashlight beam” above right of center. Look closely! I had the opacities set fairly dark when I made the screen grab. Both the “flashlight beam” and the rest of the screen can be made either more or less dark, independently, as you wish.

    Version 1.21 is a bug-fixer for version 1.20, which was in turn an upgrade over version 1.10. In 1.20, I had been playing with the colors and opacities of this and that, and I believed I had finally found a combination that was useful notwithstanding that the lowest screen brightness available in hardware, in all the Macintoshes with which I am familiar, is obnoxiously bright. The problem that required 1.21 as a fix was peculiar to slower Macintoshes — obnoxious bright patches appeared when the cursor was moving. I believe the issue is reduced, though not necessarily eliminated. See the section about bugs, immediately following.

    Known serious bugs in Red Sky:  On slow Macintoshes, with slow disc drives, small portions of the display may occasionally appear briefly at full brightness. I believe this problem is a timing issue related to how Macintoshes arrange to update their display screens, and I have not found a way to fix it completely, but I have reduced its frequency of occurrence considerably compared to earlier releases. I do not encounter the problem when running Red Sky installed on the internal disc drive of a 2006 model 13-inch Macbook; I see it in a few percent of the times I move the cursor when I am running Red Sky installed on a thumb drive plugged into a 600 MHz G3 Powerbook.  Your mileage may vary.

    If you should find any other bugs in Red Sky, by all means send me EMail.

Shareware software available for download.