Still preparing for the big shift to property lists.

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Simon Brooke 2023-04-02 12:57:26 +01:00
parent b61e7c3e8c
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<!DOCTYPE html PUBLIC ""
"">
<html><head><meta charset="UTF-8" /><title>beowulf</title><link rel="stylesheet" type="text/css" href="css/default.css" /><link rel="stylesheet" type="text/css" href="css/highlight.css" /><script type="text/javascript" src="js/highlight.min.js"></script><script type="text/javascript" src="js/jquery.min.js"></script><script type="text/javascript" src="js/page_effects.js"></script><script>hljs.initHighlightingOnLoad();</script></head><body><div id="header"><h2>Generated by <a href="https://github.com/weavejester/codox">Codox</a></h2><h1><a href="index.html"><span class="project-title"><span class="project-name">Beowulf</span> <span class="project-version">0.3.0-SNAPSHOT</span></span></a></h1></div><div class="sidebar primary"><h3 class="no-link"><span class="inner">Project</span></h3><ul class="index-link"><li class="depth-1 "><a href="index.html"><div class="inner">Index</div></a></li></ul><h3 class="no-link"><span class="inner">Topics</span></h3><ul><li class="depth-1 current"><a href="intro.html"><div class="inner"><span>beowulf</span></div></a></li><li class="depth-1 "><a href="mexpr.html"><div class="inner"><span>M-Expressions</span></div></a></li></ul><h3 class="no-link"><span class="inner">Namespaces</span></h3><ul><li class="depth-1"><div class="no-link"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>beowulf</span></div></div></li><li class="depth-2 branch"><a href="beowulf.bootstrap.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>bootstrap</span></div></a></li><li class="depth-2 branch"><a href="beowulf.cons-cell.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>cons-cell</span></div></a></li><li class="depth-2 branch"><a href="beowulf.core.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>core</span></div></a></li><li class="depth-2 branch"><a href="beowulf.gendoc.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>gendoc</span></div></a></li><li class="depth-2 branch"><a href="beowulf.host.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>host</span></div></a></li><li class="depth-2 branch"><a href="beowulf.io.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>io</span></div></a></li><li class="depth-2 branch"><a href="beowulf.manual.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>manual</span></div></a></li><li class="depth-2 branch"><a href="beowulf.oblist.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>oblist</span></div></a></li><li class="depth-2 branch"><a href="beowulf.read.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>read</span></div></a></li><li class="depth-2"><div class="no-link"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>reader</span></div></div></li><li class="depth-3 branch"><a href="beowulf.reader.char-reader.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>char-reader</span></div></a></li><li class="depth-3 branch"><a href="beowulf.reader.generate.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>generate</span></div></a></li><li class="depth-3 branch"><a href="beowulf.reader.macros.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>macros</span></div></a></li><li class="depth-3 branch"><a href="beowulf.reader.parser.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>parser</span></div></a></li><li class="depth-3"><a href="beowulf.reader.simplify.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>simplify</span></div></a></li><li class="depth-2"><a href="beowulf.scratch.html"><div class="inner"><span class="tree" style="top: -176px;"><span class="top" style="height: 185px;"></span><span class="bottom"></span></span><span>scratch</span></div></a></li></ul></div><div class="document" id="content"><div class="doc"><div class="markdown"><h1><a href="#beowulf" name="beowulf"></a>beowulf</h1>
<p>LISP 1.5 is to all Lisp dialects as Beowulf is to Emglish literature.</p>
<html><head><meta charset="UTF-8" /><title>beowulf</title><link rel="stylesheet" type="text/css" href="css/default.css" /><link rel="stylesheet" type="text/css" href="css/highlight.css" /><script type="text/javascript" src="js/highlight.min.js"></script><script type="text/javascript" src="js/jquery.min.js"></script><script type="text/javascript" src="js/page_effects.js"></script><script>hljs.initHighlightingOnLoad();</script></head><body><div id="header"><h2>Generated by <a href="https://github.com/weavejester/codox">Codox</a></h2><h1><a href="index.html"><span class="project-title"><span class="project-name">Beowulf</span> <span class="project-version">0.3.0-SNAPSHOT</span></span></a></h1></div><div class="sidebar primary"><h3 class="no-link"><span class="inner">Project</span></h3><ul class="index-link"><li class="depth-1 "><a href="index.html"><div class="inner">Index</div></a></li></ul><h3 class="no-link"><span class="inner">Topics</span></h3><ul><li class="depth-1 current"><a href="intro.html"><div class="inner"><span>beowulf</span></div></a></li><li class="depth-1 "><a href="mexpr.html"><div class="inner"><span>M-Expressions</span></div></a></li><li class="depth-1 "><a href="values.html"><div class="inner"><span>Understanding values and properties</span></div></a></li></ul><h3 class="no-link"><span class="inner">Namespaces</span></h3><ul><li class="depth-1"><div class="no-link"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>beowulf</span></div></div></li><li class="depth-2 branch"><a href="beowulf.bootstrap.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>bootstrap</span></div></a></li><li class="depth-2 branch"><a href="beowulf.cons-cell.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>cons-cell</span></div></a></li><li class="depth-2 branch"><a href="beowulf.core.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>core</span></div></a></li><li class="depth-2 branch"><a href="beowulf.gendoc.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>gendoc</span></div></a></li><li class="depth-2 branch"><a href="beowulf.host.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>host</span></div></a></li><li class="depth-2 branch"><a href="beowulf.io.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>io</span></div></a></li><li class="depth-2 branch"><a href="beowulf.manual.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>manual</span></div></a></li><li class="depth-2 branch"><a href="beowulf.oblist.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>oblist</span></div></a></li><li class="depth-2 branch"><a href="beowulf.read.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>read</span></div></a></li><li class="depth-2"><div class="no-link"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>reader</span></div></div></li><li class="depth-3 branch"><a href="beowulf.reader.char-reader.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>char-reader</span></div></a></li><li class="depth-3 branch"><a href="beowulf.reader.generate.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>generate</span></div></a></li><li class="depth-3 branch"><a href="beowulf.reader.macros.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>macros</span></div></a></li><li class="depth-3 branch"><a href="beowulf.reader.parser.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>parser</span></div></a></li><li class="depth-3"><a href="beowulf.reader.simplify.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>simplify</span></div></a></li><li class="depth-2"><a href="beowulf.scratch.html"><div class="inner"><span class="tree" style="top: -176px;"><span class="top" style="height: 185px;"></span><span class="bottom"></span></span><span>scratch</span></div></a></li></ul></div><div class="document" id="content"><div class="doc"><div class="markdown"><h1><a href="#beowulf" name="beowulf"></a>beowulf</h1>
<p>LISP 1.5 is to all Lisp dialects as Beowulf is to English literature.</p>
<h2><a href="#what-this-is" name="what-this-is"></a>What this is</h2>
<p>A work-in-progress towards an implementation of Lisp 1.5 in Clojure. The objective is to build a complete and accurate implementation of Lisp 1.5 as described in the manual, with, in so far as is possible, exactly the same bahaviour - except as documented below.</p>
<h3><a href="#status" name="status"></a>Status</h3>
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-s, --strict Strictly interpret the Lisp 1.5 language, without extensions.
</code></pre>
<p>To end a session, type <code>STOP</code> at the command prompt.</p>
<h3><a href="#reader-macros" name="reader-macros"></a>Reader macros</h3>
<p>Currently I dont have </p>
<h3><a href="#functions-and-symbols-implemented" name="functions-and-symbols-implemented"></a>Functions and symbols implemented</h3>
<p>The following functions and symbols are implemented:</p>
<table>

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<!DOCTYPE html PUBLIC ""
"">
<html><head><meta charset="UTF-8" /><title>M-Expressions</title><link rel="stylesheet" type="text/css" href="css/default.css" /><link rel="stylesheet" type="text/css" href="css/highlight.css" /><script type="text/javascript" src="js/highlight.min.js"></script><script type="text/javascript" src="js/jquery.min.js"></script><script type="text/javascript" src="js/page_effects.js"></script><script>hljs.initHighlightingOnLoad();</script></head><body><div id="header"><h2>Generated by <a href="https://github.com/weavejester/codox">Codox</a></h2><h1><a href="index.html"><span class="project-title"><span class="project-name">Beowulf</span> <span class="project-version">0.3.0-SNAPSHOT</span></span></a></h1></div><div class="sidebar primary"><h3 class="no-link"><span class="inner">Project</span></h3><ul class="index-link"><li class="depth-1 "><a href="index.html"><div class="inner">Index</div></a></li></ul><h3 class="no-link"><span class="inner">Topics</span></h3><ul><li class="depth-1 "><a href="intro.html"><div class="inner"><span>beowulf</span></div></a></li><li class="depth-1 current"><a href="mexpr.html"><div class="inner"><span>M-Expressions</span></div></a></li></ul><h3 class="no-link"><span class="inner">Namespaces</span></h3><ul><li class="depth-1"><div class="no-link"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>beowulf</span></div></div></li><li class="depth-2 branch"><a href="beowulf.bootstrap.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>bootstrap</span></div></a></li><li class="depth-2 branch"><a href="beowulf.cons-cell.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>cons-cell</span></div></a></li><li class="depth-2 branch"><a href="beowulf.core.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>core</span></div></a></li><li class="depth-2 branch"><a href="beowulf.gendoc.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>gendoc</span></div></a></li><li class="depth-2 branch"><a href="beowulf.host.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>host</span></div></a></li><li class="depth-2 branch"><a href="beowulf.io.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>io</span></div></a></li><li class="depth-2 branch"><a href="beowulf.manual.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>manual</span></div></a></li><li class="depth-2 branch"><a href="beowulf.oblist.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>oblist</span></div></a></li><li class="depth-2 branch"><a href="beowulf.read.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>read</span></div></a></li><li class="depth-2"><div class="no-link"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>reader</span></div></div></li><li class="depth-3 branch"><a href="beowulf.reader.char-reader.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>char-reader</span></div></a></li><li class="depth-3 branch"><a href="beowulf.reader.generate.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>generate</span></div></a></li><li class="depth-3 branch"><a href="beowulf.reader.macros.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>macros</span></div></a></li><li class="depth-3 branch"><a href="beowulf.reader.parser.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>parser</span></div></a></li><li class="depth-3"><a href="beowulf.reader.simplify.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>simplify</span></div></a></li><li class="depth-2"><a href="beowulf.scratch.html"><div class="inner"><span class="tree" style="top: -176px;"><span class="top" style="height: 185px;"></span><span class="bottom"></span></span><span>scratch</span></div></a></li></ul></div><div class="document" id="content"><div class="doc"><div class="markdown"><h1><a href="#m-expressions" name="m-expressions"></a>M-Expressions</h1>
<html><head><meta charset="UTF-8" /><title>M-Expressions</title><link rel="stylesheet" type="text/css" href="css/default.css" /><link rel="stylesheet" type="text/css" href="css/highlight.css" /><script type="text/javascript" src="js/highlight.min.js"></script><script type="text/javascript" src="js/jquery.min.js"></script><script type="text/javascript" src="js/page_effects.js"></script><script>hljs.initHighlightingOnLoad();</script></head><body><div id="header"><h2>Generated by <a href="https://github.com/weavejester/codox">Codox</a></h2><h1><a href="index.html"><span class="project-title"><span class="project-name">Beowulf</span> <span class="project-version">0.3.0-SNAPSHOT</span></span></a></h1></div><div class="sidebar primary"><h3 class="no-link"><span class="inner">Project</span></h3><ul class="index-link"><li class="depth-1 "><a href="index.html"><div class="inner">Index</div></a></li></ul><h3 class="no-link"><span class="inner">Topics</span></h3><ul><li class="depth-1 "><a href="intro.html"><div class="inner"><span>beowulf</span></div></a></li><li class="depth-1 current"><a href="mexpr.html"><div class="inner"><span>M-Expressions</span></div></a></li><li class="depth-1 "><a href="values.html"><div class="inner"><span>Understanding values and properties</span></div></a></li></ul><h3 class="no-link"><span class="inner">Namespaces</span></h3><ul><li class="depth-1"><div class="no-link"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>beowulf</span></div></div></li><li class="depth-2 branch"><a href="beowulf.bootstrap.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>bootstrap</span></div></a></li><li class="depth-2 branch"><a href="beowulf.cons-cell.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>cons-cell</span></div></a></li><li class="depth-2 branch"><a href="beowulf.core.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>core</span></div></a></li><li class="depth-2 branch"><a href="beowulf.gendoc.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>gendoc</span></div></a></li><li class="depth-2 branch"><a href="beowulf.host.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>host</span></div></a></li><li class="depth-2 branch"><a href="beowulf.io.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>io</span></div></a></li><li class="depth-2 branch"><a href="beowulf.manual.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>manual</span></div></a></li><li class="depth-2 branch"><a href="beowulf.oblist.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>oblist</span></div></a></li><li class="depth-2 branch"><a href="beowulf.read.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>read</span></div></a></li><li class="depth-2"><div class="no-link"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>reader</span></div></div></li><li class="depth-3 branch"><a href="beowulf.reader.char-reader.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>char-reader</span></div></a></li><li class="depth-3 branch"><a href="beowulf.reader.generate.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>generate</span></div></a></li><li class="depth-3 branch"><a href="beowulf.reader.macros.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>macros</span></div></a></li><li class="depth-3 branch"><a href="beowulf.reader.parser.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>parser</span></div></a></li><li class="depth-3"><a href="beowulf.reader.simplify.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>simplify</span></div></a></li><li class="depth-2"><a href="beowulf.scratch.html"><div class="inner"><span class="tree" style="top: -176px;"><span class="top" style="height: 185px;"></span><span class="bottom"></span></span><span>scratch</span></div></a></li></ul></div><div class="document" id="content"><div class="doc"><div class="markdown"><h1><a href="#m-expressions" name="m-expressions"></a>M-Expressions</h1>
<p>M-Expressions (mexprs) are the grammar which John McCarthy origininally used to write Lisp, and the grammar in which many of the function definitions in the <a href="https://www.softwarepreservation.org/projects/LISP/book/LISP%201.5%20Programmers%20Manual.pdf">Lisp 1.5 Programmers Manual</a> are stated. However, I have not seen anywhere a claim that Lisp 1.5 could <em>read</em> M-Expressions, and it is not clear to me whether it was even planned that it should do so.</p>
<p>Rather, it seems to me probably that M-Expressions were only ever a grammar intended to be written on paper, like <a href="https://en.wikipedia.org/wiki/Backus%E2%80%93Naur_form">Backus Naur Form</a>, to describe and to reason about algorithms.</p>
<p>I set out to make Beowulf read M-Expressions essentially out of curiousity, to see whether it could be done. I had this idea that if it could be done, I could implement most of Lisp 1.5 simply by copying in the M-Expression definitions out of the manual.</p>

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<html><head><meta charset="UTF-8" /><title>Understanding values and properties</title><link rel="stylesheet" type="text/css" href="css/default.css" /><link rel="stylesheet" type="text/css" href="css/highlight.css" /><script type="text/javascript" src="js/highlight.min.js"></script><script type="text/javascript" src="js/jquery.min.js"></script><script type="text/javascript" src="js/page_effects.js"></script><script>hljs.initHighlightingOnLoad();</script></head><body><div id="header"><h2>Generated by <a href="https://github.com/weavejester/codox">Codox</a></h2><h1><a href="index.html"><span class="project-title"><span class="project-name">Beowulf</span> <span class="project-version">0.3.0-SNAPSHOT</span></span></a></h1></div><div class="sidebar primary"><h3 class="no-link"><span class="inner">Project</span></h3><ul class="index-link"><li class="depth-1 "><a href="index.html"><div class="inner">Index</div></a></li></ul><h3 class="no-link"><span class="inner">Topics</span></h3><ul><li class="depth-1 "><a href="intro.html"><div class="inner"><span>beowulf</span></div></a></li><li class="depth-1 "><a href="mexpr.html"><div class="inner"><span>M-Expressions</span></div></a></li><li class="depth-1 current"><a href="values.html"><div class="inner"><span>Understanding values and properties</span></div></a></li></ul><h3 class="no-link"><span class="inner">Namespaces</span></h3><ul><li class="depth-1"><div class="no-link"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>beowulf</span></div></div></li><li class="depth-2 branch"><a href="beowulf.bootstrap.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>bootstrap</span></div></a></li><li class="depth-2 branch"><a href="beowulf.cons-cell.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>cons-cell</span></div></a></li><li class="depth-2 branch"><a href="beowulf.core.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>core</span></div></a></li><li class="depth-2 branch"><a href="beowulf.gendoc.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>gendoc</span></div></a></li><li class="depth-2 branch"><a href="beowulf.host.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>host</span></div></a></li><li class="depth-2 branch"><a href="beowulf.io.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>io</span></div></a></li><li class="depth-2 branch"><a href="beowulf.manual.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>manual</span></div></a></li><li class="depth-2 branch"><a href="beowulf.oblist.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>oblist</span></div></a></li><li class="depth-2 branch"><a href="beowulf.read.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>read</span></div></a></li><li class="depth-2"><div class="no-link"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>reader</span></div></div></li><li class="depth-3 branch"><a href="beowulf.reader.char-reader.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>char-reader</span></div></a></li><li class="depth-3 branch"><a href="beowulf.reader.generate.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>generate</span></div></a></li><li class="depth-3 branch"><a href="beowulf.reader.macros.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>macros</span></div></a></li><li class="depth-3 branch"><a href="beowulf.reader.parser.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>parser</span></div></a></li><li class="depth-3"><a href="beowulf.reader.simplify.html"><div class="inner"><span class="tree"><span class="top"></span><span class="bottom"></span></span><span>simplify</span></div></a></li><li class="depth-2"><a href="beowulf.scratch.html"><div class="inner"><span class="tree" style="top: -176px;"><span class="top" style="height: 185px;"></span><span class="bottom"></span></span><span>scratch</span></div></a></li></ul></div><div class="document" id="content"><div class="doc"><div class="markdown"><h1><a href="#understanding-values-and-properties" name="understanding-values-and-properties"></a>Understanding values and properties</h1>
<p>I had had the naive assumption that entries on the object list had their CAR pointing to the symbol and their CDR pointing to the related value. Consequently, I could not work out where the property list went. More careful reading of the text implies, but does not explicitly state, that my naive assumption is wrong.</p>
<p>Instead, it appears that the <code>CAR</code> points to the symbol, as expected, but the <code>CAR</code> points to the property list; and that on the property list there are privileged properties at least as follows:</p>
<dl>
<dt>APVAL</dt>
<dd>the simple straightforward ordinary value of the symbol, considered a variable;</dd>
<dt>EXPR</dt>
<dd>the definition of the function considered as a normal lambda expression (arguments to be evaluated before applying);</dd>
<dt>FEXPR</dt>
<dd>the definition of a function which should be applied to unevaluated arguments;</dd>
<dt>SUBR</dt>
<dd>the definition of a complied subroutine which should be applied to evaluated arguments;</dd>
<dt>FSUBR</dt>
<dd>the definition of a complied subroutine which should be applied to unevaluated arguments.</dd>
</dl>
<p>I think there was also another privileged property value which contained the property considered as a constant, but I havent yet confirmed that.</p>
<p>From this it would seem that Lisp 1.5 was not merely a <a href="http://xahlee.info/emacs/emacs/lisp1_vs_lisp2.html">Lisp 2</a> but in fact a Lisp 6, with six effectively first class namespaces. In fact its not as bad as that, because of the way <a href="https://www.softwarepreservation.org/projects/LISP/book/LISP%201.5%20Programmers%20Manual.pdf#page=79"><code>EVAL</code></a> is evaluated.</p>
<p>Essentially the properties are tried in turn, and only the first value found is used. Thus the heirarchy is</p>
<ol>
<li>APVAL</li>
<li>EXPR</li>
<li>FEXPR</li>
<li>SUBR</li>
<li>FSUBR</li>
</ol>
<p>This means that, while the other potential values can be retrieved from the property list, interpreted definitions (if present) will always be preferred to uninterpreted definitions, and lambda function definitions (which evaluate their arguments), where present, will always be preferred to non-lamda definitions, which dont.</p>
<p><strong>BUT NOTE THAT</strong> the <code>APVAL</code> value is saught only when seeking a variable value for the symbol, and the others only when seeking a function value, so Lisp 1.5 is a Lisp 2, not a Lisp 1.</p>
<p>Versions of Beowulf up to and including 0.2.1 used the naive understanding of the architecture; version 0.3.0 <em>should</em> use the corrected version.</p></div></div></div></body></html>