HISTORY.md

History of Pixley Distribution

While The Pixley Programming Language notes the changes, over time, to the Pixley language itself, this file notes the changes to this distribution: implementation, documentation, example programs, and other "goodies".

1.0

• Initial distribution, implementing Pixley 1.0.

1.1

• Changed implementations to implement Pixley 1.1.

• An enlarged test suite (previously mentioned).

• A REPL (read-eval-print loop, or "interactive mode" interpreter), written in Scheme.

• A statistics generator, written in Scheme, which counts the cons cells, symbol instances, and unique symbols present in a given s-expression. This was to measure the complexity of the Pixley interpreter.

• A Mini-Scheme driver. During my adventures in getting programs to run under AmigaOS 1.3, I compiled Mini-Scheme thereunder, and got Pixley to run under it by including the Pixley interpreter in Mini-Scheme's init.scm file and invoking it therein. From this I conclude that, although I have not confirmed this is in a solid way by looking at the spec or anything, Pixley is also a strict subset of R4RS Scheme.

2.0

• Changed implementations to implement Pixley 2.0.

• Bourne Shell scripts to run Pixley programs which are stored in individual files. pixley.sh runs either a self-contained Pixley program from a single file, or evaluates a Pixley file to a function value and applies it to an S-expression stored in a second file. scheme.sh does the same thing, but with Scheme, as a sanity-check. By default these scripts use plt-r5rs for the Scheme interpreter, but that can be changed with an environment variable.

• A P-Normalizer written in Pixley, probably the first non-trivial Pixley program to be written, aside from the Pixley interpreter itself. P-Normal Pixley is a simplified version of Pixley where let* can only bind one identifer to one value and cond can only make one test, like Scheme's if. This form is described more fully in the Falderal literate test suite for the P-Normalizer.

• Test suites, written in Falderal, for both Pixley and the P-Normalizer. The original test suite written in Scheme, which runs successively deeper nested copies of the Pixley interpreter, is still included in the distribution.

• A few other standalone Pixley examples, including reverse.pix, which reverses the given list.

2.0 revision 2012.0219

• The Bourne shell scripts pixley.sh and scheme.sh were replaced by a single script tower.sh. The idea behind this script is that it lets you constuct a "tower of interpreters" from a sequence of text files which contain S-expressions. The first such S-expression is interpreted as Scheme, and may evaluate to a function value; the second such will be interpreted by that function, and may evaluate to another function value, and so forth, until there is an S-expression that evaluates to something besides a function value (and that result will be printed to standard output and tower.sh will terminate.)

• tower.sh officially supports three implementations of Scheme that can be used as the base interpreter: plt-r5rs from the Racket distribution, tinyscheme, and miniscm version 0.85p1 (from our fork of the project on GitHub.) Support for Scheme implementations is (more or less) capability-based, so adding support for other implementations should not be difficult (especially if they are similar to the three already supported.)

• The test suite was put into Falderal 0.6 format and now uses tower.sh to run each test case. By default, it uses plt-r5rs, but can be told to use any of the Scheme implementations that tower.sh supports. (Note: there is currently a failure when running one of the tests on a Pixley interpreter on a Pixley interpreter on miniscm that I have yet to track down.)

• To match the expectations of tower.sh, the Pixley self-interpreter was refactored to evaluate to a function value of one argument. It was also simplified slightly, removing an unnecessary nested cond.

• Various dialects of Pixley have been defined and described, and collected in the dialect directory of the distribution. The dialects include Pifxley, which supports an if construct instead of cond; there is a Pixley interpreter written in Pifxley, and a Pifxley self-interpreter. There is also a dialect called Crabwell which allows values to be bound to, not just symbols, but arbitrary S-expressions.

• A bug (a missing case) was fixed in the P-Normalizer.

• The main Pixley documentation (what you're reading now) was converted to Markdown format.

• Source code in the Pixley distribution was placed under a BSD-style license.

2.0 revision 2013.1024

• Funny story! Remember when I said I was writing writing stuff in C to compile with DICE C under AmigaOS 1.3, and that what I decided to write was a Pixley interpreter in C? Well, that implementation of Pixley, called mignon, has finally been included in the Pixley distribution.

• Another implementation of Pixley, this time in Haskell and called haney, has also been included in the Pixley distribution.

• The tower.sh script has been refactored, since honestly it was kind of grody. The abstraction layer which tries to make different implementations of Scheme behave the same has been split off into scheme-adapter.sh, while the responsibility of tower.sh itself is only to build and run the tower of interpreters. In addition to plt-r5rs, Mini-Scheme, and Tinyscheme, scheme-adapter.sh also supports the Husk Scheme interpreter. Finally, scheme-adapter.sh supports mignon and haney as well; even though they're not proper Scheme interpreters, they can be used as the base interpreter for a tower of Pixley interpreters.

• The test suite has been modernized (for whatever "modern" means for Falderal) and enriched to handle testing these extra implementations.

2.0 revision 2015.0101

(This also includes updates from revision 2014.0819 which I neglected to list here previously.)

• A new implementation of Pixley, in Javascript, which runs in a web browser which supports Web Workers. As a bonus, it can depict the Pixley program as a series of nested, coloured rectangles. You can see it online here: Pixley installation at Cat's Eye Technologies.

• Wrappers to allow pixley.scm to be run under Scheme48 and the CHICKEN Scheme interpreter.

• The test suite tries to find a reasonable Scheme implementation to run under.

• Syntax for tests updated to Falderal 0.10.

• with-input-from-file is an optional R5RS, so change the Scheme programs to not rely on it.

2.0 revision 2015.0723

• Small changes to the Javascript implementation.

2.0 revision 2017.1110

• Put all example programs as discrete files in the eg/ directory.

• Small changes to the Javascript implementation.

2.0 revision 2018.0622

• Split this HISTORY file off from The Pixley Programming Language.

• Added a build.seq which details how to build mignon under AmigaDOS 1.3 using DICE C.

• Added a launch-pixley.js file to the pixley.js demo, which is responsible for creating the UI, instead of coding it in HTML.

2.0 revision 2023.0919

• Refactored launch-pixley.js to eliminate long lines.