245 lines
12 KiB
HTML
245 lines
12 KiB
HTML
<!doctype html>
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<html>
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<head>
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<meta charset="utf-8">
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<title>Thun</title>
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<link rel="stylesheet" href="/css/font/fonts.css">
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<link rel="stylesheet" href="/css/site.css">
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<script src="/Joy.js"></script>
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</head>
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<body>
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<div id="joy_interpreter"></div>
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<h1>Thun</h1>
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<p>A Dialect of Joy.</p>
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<p>Version 0.5.0</p>
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<blockquote>
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<p>Simple pleasures are the best.</p>
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</blockquote>
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<p><a href="https://en.wikipedia.org/wiki/Joy_%28programming_language%29">Joy</a> is a
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programming language created by Manfred von Thun that is easy to use and
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understand and has many other nice properties. <strong>Thun</strong> is a dialect of
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Joy that attempts to stay very close to the spirit of Joy but does not
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precisely match the behaviour of the original version written in C. It
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started as a Python project called "Joypy", but after someone claimed that
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name on PyPI before me I renamed it to Thun in honor of Manfred Von Thun.
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Now there are interpreters implemented in several additional languages
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(C, Nim, Prolog, Rust).</p>
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<p>Joy is:</p>
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<ul>
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<li><a href="https://en.wikipedia.org/wiki/Purely_functional_programming">Purely Functional</a></li>
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<li><a href="https://en.wikipedia.org/wiki/Stack-oriented_programming_language">Stack-based</a></li>
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<li><a href="https://en.wikipedia.org/wiki/Concatenative_programming_language">Concatinative</a>
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(See also <a href="http://www.concatenative.org/wiki/view/Concatenative%20language">concatenative.org</a>)</li>
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<li><a href="https://joypy.osdn.io/notebooks/Categorical.html">Categorical</a></li>
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</ul>
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<p>The best source (no pun intended) for learning about Joy is the
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information made available at the
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<a href="http://www.latrobe.edu.au/humanities/research/research-projects/past-projects/joy-programming-language">website of La Trobe University</a>
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| <a href="https://www.kevinalbrecht.com/code/joy-mirror/">(mirror)</a>
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which contains source code for the original C interpreter, Joy language source code for various functions,
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and a great deal of fascinating material mostly written by Von Thun on
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Joy and its deeper facets as well as how to program in it and several
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interesting aspects. It's quite a treasure trove.</p>
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<ul>
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<li><a href="https://en.wikipedia.org/wiki/Joy_%28programming_language%29">Wikipedia entry for Joy</a></li>
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<li><a href="http://www.latrobe.edu.au/humanities/research/research-projects/past-projects/joy-programming-language">Homepage at La Trobe University</a>
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<a href="https://www.kevinalbrecht.com/code/joy-mirror/">(Kevin Albrecht's mirror)</a></li>
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<li><a href="https://web.archive.org/web/20220411010035/https://joypy.osdn.io/">The original Thun/Joypy site</a></li>
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</ul>
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<h2>Example Code</h2>
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<p>Here is an example of Joy code. This function <code>square_spiral</code> accepts
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two integers and increments or decrements one of them such that the new
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pair of numbers is the next coordinate pair in a square spiral (like the
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kind used to construct an <a href="https://en.wikipedia.org/wiki/Ulam_spiral">Ulam Spiral</a>).
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For more information see <a href="/notebooks/Square_Spiral.html">Square Spiral Example Joy Code</a>.</p>
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<pre><code>square_spiral [_p] [_then] [_else] ifte
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_p [_p0] [_p1] and
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_p0 [abs] ii <=
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_p1 [<>] [pop !-] or
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_then [ !-] [[++]] [[--]] ifte dip
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_else [pop !-] [--] [++] ifte
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</code></pre>
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<p>It might seem unreadable but with familiarity it becomes as legible as any other notation.</p>
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<h2>Project Hosted on <a href="https://git.sr.ht/~sforman/Thun">SourceHut</a></h2>
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<ul>
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<li><a href="https://git.sr.ht/~sforman/Thun">Source Repository</a>
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(<a href="https://github.com/calroc/Thun">mirror</a>)</li>
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<li><a href="https://todo.sr.ht/~sforman/thun-der">Bug tracker</a>
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(<a href="https://osdn.net/projects/joypy/ticket/">old tracker</a>)</li>
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<li><a href="https://osdn.net/projects/joypy/forums/">Forums</a></li>
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<li><a href="https://osdn.net/projects/joypy/lists/">Mailing list</a></li>
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</ul>
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<h2>Documentation</h2>
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<p>This document describes Joy in a general way below, however most of the
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documentation is in the form of <a href="/notebooks/index.html">Jupyter Notebooks</a>
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that go into more detail.</p>
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<p><strong><a href="/notebooks/index.html">Jupyter Notebooks</a></strong></p>
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<p>There's also a <a href="/FuncRef.html">Function Reference</a> that lists each
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function and combinator by name and gives a brief description. (It's
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usually out of date, I'm working on it.)</p>
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<p><strong><a href="/FuncRef.html">Function Reference</a></strong></p>
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<h3>Building the Docs</h3>
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<p>Run <code>make</code> in the <code>docs</code> directory. (This is a lie, it's more complex than
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that. Really you need to run (GNU) make in the <code>docs/notebooks</code> and
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<code>docs/reference</code> dirs first, <em>then</em> run <code>make</code> in the <code>docs</code> directory.)</p>
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<h2>Directory structure</h2>
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<pre><code>Thun
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|-- LICENSE - GPLv3
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|-- README.md - this file
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|-- archive
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| |-- Joy-Programming.zip
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| `-- README
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|-- docs
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| |-- dep-graphs - Generated dependency graphs.
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| |-- html - Generated HTML docs.
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| |-- notebooks - Jupyter Notebooks and supporting modules
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| `-- reference - Docs for each function.
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|-- implementations
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| |-- defs.txt - common Joy definitions for all interpreters
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| |-- C - interpreter
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| |-- GNUProlog - interpreter
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| | type inference
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| | work-in-progress compiler
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| |
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| |-- Nim - interpreter
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| |-- Ocaml - work-in-progress interpreter
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| `-- Python - interpreter
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`-- joy_code - Source code written in Joy.
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`-- bigints
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`-- bigints.joy
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</code></pre>
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<h2>Installation</h2>
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<p>Clone the repo and follow the instructions in the individual
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<code>implementations</code> directories. There isn't really any installation. You
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can put the binaries in your <code>PATH</code>.</p>
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<p>(I had the Python package set up to upload to PyPI as "Thun", but the
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whole Python distribution story seems unsettled at the moment (2023) so
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I've gone back to the <em>old ways</em>: there is a single script <code>joy.py</code>
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that gets modified (<code>defs.txt</code> is inserted) to create a <code>joy</code> script
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that uses the "shebang" trick to pretend to be a binary. In other words,
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run <code>make</code> and put the resulting <code>joy</code> script in your PATH, if that's
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what you want to do. In a year or two the Python folks will have sorted
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things out and we can go back to <code>pip install Thun</code> or whatever.)</p>
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<h2>Basics of Joy</h2>
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<p>The original Joy has several datatypes (such as strings and sets)
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but the Thun dialect currently only uses four:</p>
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<ul>
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<li>Integers, signed and unbounded by machine word length (they are
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<a href="https://en.wikipedia.org/wiki/Arbitrary-precision_arithmetic">bignums</a>.)</li>
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<li>Boolean values <code>true</code> and <code>false</code>.</li>
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<li>Lists quoted in <code>[</code> and <code>]</code> brackets.</li>
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<li>Symbols (names).</li>
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</ul>
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<p>Joy is built around three things: a <strong>stack</strong> of data items, an <strong>expression</strong>
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representing a program to evaluate, and a <strong>dictionary</strong> of named functions.</p>
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<h3>Stack</h3>
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<p>Joy is <a href="https://en.wikipedia.org/wiki/Stack-oriented_programming_language">stack-based</a>.
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There is a single main <strong>stack</strong> that holds data items, which can be integers, bools,
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symbols (names), or sequences of data items enclosed in square brackets (<code>[</code> or <code>]</code>).</p>
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<p>We use the terms "stack", "quote", "sequence",
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"list", and others to mean the same thing: a simple linear datatype that
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permits certain operations such as iterating and pushing and popping
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values from (at least) one end.</p>
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<blockquote>
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<p>In describing Joy I have used the term quotation to describe all of the
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above, because I needed a word to describe the arguments to combinators
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which fulfill the same role in Joy as lambda abstractions (with
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variables) fulfill in the more familiar functional languages. I use the
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term list for those quotations whose members are what I call literals:
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numbers, characters, truth values, sets, strings and other quotations.
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All these I call literals because their occurrence in code results in
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them being pushed onto the stack. But I also call [London Paris] a list.
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So, [dup *] is a quotation but not a list.</p>
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</blockquote>
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<p>From <a href="http://archive.vector.org.uk/art10000350">"A Conversation with Manfred von Thun" w/ Stevan Apter</a></p>
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<h3>Expression</h3>
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<p>A Joy <strong>expression</strong> is just a sequence or list of items. Sequences
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intended as programs are called "quoted programs". Evaluation proceeds
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by iterating through the terms in an expression putting all literals
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(integers, bools, or lists) onto the main stack and executing functions
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named by symbols as they are encountered. Functions receive the current
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stack, expression, and dictionary and return the next stack, expression,
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and dictionary.</p>
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<h3>Dictionary</h3>
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<p>The <strong>dictionary</strong> associates symbols (names) with Joy expressions that
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define the available functions of the Joy system. Together the stack,
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expression, and dictionary are the entire state of the Joy interpreter.</p>
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<h3>Interpreter</h3>
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<p>The Joy interpreter is extrememly simple. It accepts a stack, an
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expression, and a dictionary, and it iterates through the expression
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putting values onto the stack and delegating execution to functions which
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it looks up in the dictionary.</p>
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<p><img alt="Joy Interpreter Flowchart" src="/joy_interpreter_flowchart.svg"></p>
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<p>All control flow works by
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<a href="https://en.wikipedia.org/wiki/Continuation-passing_style">Continuation Passing Style</a>.
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<strong>Combinators</strong> (see below) alter control flow by prepending quoted programs to the pending
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expression (aka "continuation".)</p>
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<hr>
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<p>From here it kinda falls apart...</p>
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<h3>Literals and Simple Functions</h3>
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<p>TODO</p>
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<h3>Combinators</h3>
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<p>The main loop is very simple as most of the action happens through what
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are called <strong>combinators</strong>. These are functions which accept quoted programs on the
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stack and run them in various ways. These combinators reify specific
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control-flow patterns (such as <code>ifte</code> which is like <code>if.. then.. else..</code> in other
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languages.) Combinators receive the current
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expession in addition to the stack and return the next expression. They
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work by changing the pending expression the interpreter is about to
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execute. (The combinators could work by making recursive calls to the
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interpreter and all intermediate state would be held in the call stack of
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the implementation language, in this joy implementation they work instead
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by changing the pending expression and intermediate state is put there.)</p>
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<pre><code>joy? 23 [0 >] [dup --] while
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23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
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</code></pre>
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<h3>Core Words</h3>
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<p>This is the <em>basis</em> set of functions, the rest of functions in the Thun
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dialect of Joy are defined in terms of these:</p>
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<pre><code>branch
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dip
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i
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loop
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clear
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concat
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cons
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dup
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first
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pop
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rest
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stack
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swaack
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swap
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truthy
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inscribe
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+ - * / %
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< > >= <= != <> =
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lshift rshift
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</code></pre>
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<hr>
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<p>Copyright © 2014 - 2023 Simon Forman</p>
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<p>This file is part of Thun</p>
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<p>Thun is free software: you can redistribute it and/or modify it under the
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terms of the GNU General Public License as published by the Free Software
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Foundation, either version 3 of the License, or (at your option) any
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later version.</p>
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<p>Thun is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
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details.</p>
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<p>You should have received a copy of the GNU General Public License along
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with Thun. If not see <a href="http://www.gnu.org/licenses/">http://www.gnu.org/licenses/</a>.</p>
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<script>var joy_interpreter = Elm.Main.init({node: document.getElementById('joy_interpreter')});</script>
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</body>
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</html>
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