mirror of
https://github.com/ganelson/inform.git
synced 2024-05-19 17:39:23 +03:00
124 lines
16 KiB
HTML
124 lines
16 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
|
|
<html>
|
|
<head>
|
|
<title>Equality Schemas</title>
|
|
<link href="../docs-assets/Breadcrumbs.css" rel="stylesheet" rev="stylesheet" type="text/css">
|
|
<meta name="viewport" content="width=device-width initial-scale=1">
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
|
|
<meta http-equiv="Content-Language" content="en-gb">
|
|
|
|
<link href="../docs-assets/Contents.css" rel="stylesheet" rev="stylesheet" type="text/css">
|
|
<link href="../docs-assets/Progress.css" rel="stylesheet" rev="stylesheet" type="text/css">
|
|
<link href="../docs-assets/Navigation.css" rel="stylesheet" rev="stylesheet" type="text/css">
|
|
<link href="../docs-assets/Fonts.css" rel="stylesheet" rev="stylesheet" type="text/css">
|
|
<link href="../docs-assets/Base.css" rel="stylesheet" rev="stylesheet" type="text/css">
|
|
<link href="../docs-assets/Colours.css" rel="stylesheet" rev="stylesheet" type="text/css">
|
|
|
|
</head>
|
|
<body class="commentary-font">
|
|
<nav role="navigation">
|
|
<h1><a href="../index.html">
|
|
<img src="../docs-assets/Inform.png" height=72">
|
|
</a></h1>
|
|
<ul><li><a href="../index.html">home</a></li>
|
|
</ul><h2>Compiler</h2><ul>
|
|
<li><a href="../structure.html">structure</a></li>
|
|
<li><a href="../inbuildn.html">inbuild</a></li>
|
|
<li><a href="../inform7n.html">inform7</a></li>
|
|
<li><a href="../intern.html">inter</a></li>
|
|
<li><a href="../services.html">services</a></li>
|
|
<li><a href="../secrets.html">secrets</a></li>
|
|
</ul><h2>Other Tools</h2><ul>
|
|
<li><a href="../inblorbn.html">inblorb</a></li>
|
|
<li><a href="../indocn.html">indoc</a></li>
|
|
<li><a href="../inform6.html">inform6</a></li>
|
|
<li><a href="../inpolicyn.html">inpolicy</a></li>
|
|
</ul><h2>Resources</h2><ul>
|
|
<li><a href="../extensions.html">extensions</a></li>
|
|
<li><a href="../kits.html">kits</a></li>
|
|
</ul><h2>Repository</h2><ul>
|
|
<li><a href="https://github.com/ganelson/inform"><img src="../docs-assets/github.png" height=18> github</a></li>
|
|
</ul><h2>Related Projects</h2><ul>
|
|
<li><a href="../../../inweb/index.html">inweb</a></li>
|
|
<li><a href="../../../intest/index.html">intest</a></li>
|
|
|
|
</ul>
|
|
</nav>
|
|
<main role="main">
|
|
<!--Weave of 'Equality Schemas' generated by Inweb-->
|
|
<div class="breadcrumbs">
|
|
<ul class="crumbs"><li><a href="../index.html">Home</a></li><li><a href="../inform7n.html">Inform7</a></li><li><a href="index.html">runtime</a></li><li><a href="index.html#2">Chapter 2: Emission</a></li><li><b>Equality Schemas</b></li></ul></div>
|
|
<p class="purpose">To define how to compile a comparison of two values.</p>
|
|
|
|
<p class="commentary firstcommentary"><a id="SP1" class="paragraph-anchor"></a><b>§1. </b>For most word-value kinds, it's easy to compare two values to see if they are
|
|
equal: all we need is the <span class="extract"><span class="extract-syntax">==</span></span> operator. But for pointer-value kinds, that
|
|
would simply tell us whether they point to the same block of data on the
|
|
heap, whereas we need in fact to compare the blocks they point to. So the
|
|
kind system makes it possible for each individual kind to decide how values
|
|
should be compared, returning an I6 schema prototype to compare <span class="extract"><span class="extract-syntax">*1</span></span> and <span class="extract"><span class="extract-syntax">*2</span></span>.
|
|
</p>
|
|
|
|
<p class="commentary">What happens at run-time when we test to see if value V equals value W,
|
|
or change storage object S so that it now contains value T, depends on the
|
|
kind of values we are discussing. If there were only word-based values in
|
|
Inform (as was the case until September 2007), there would be little to
|
|
do here, as the comparison would simply compile to <span class="extract"><span class="extract-syntax">V == W</span></span>, while the
|
|
storage would be a matter of either <span class="extract"><span class="extract-syntax">S = W;</span></span> or some more exotic case
|
|
along the lines of <span class="extract"><span class="extract-syntax">StorageRoutineWrite(S, W);</span></span>.
|
|
</p>
|
|
|
|
<p class="commentary">But once pointers to blocks are allowed, this becomes more interesting.
|
|
Now the comparison needs to be a deep one, that is, we want to test whether
|
|
two texts (say) have the same textual content — not whether we are
|
|
holding two pointers to the same blocks in memory, which is what a simple
|
|
comparison would achieve. Such a test is called "deep comparison", and
|
|
similarly, we must assign by transferring the contents of the blocks of
|
|
data, not merely the pointer to them, which is a "deep copy".
|
|
</p>
|
|
|
|
<pre class="displayed-code all-displayed-code code-font">
|
|
<span class="identifier-syntax">text_stream</span><span class="plain-syntax"> *</span><span class="function-syntax">EqualitySchemas::interpret_equality</span><span class="plain-syntax">(</span><span class="identifier-syntax">kind</span><span class="plain-syntax"> *</span><span class="identifier-syntax">left</span><span class="plain-syntax">, </span><span class="identifier-syntax">kind</span><span class="plain-syntax"> *</span><span class="identifier-syntax">right</span><span class="plain-syntax">) {</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">LOGIF</span><span class="plain-syntax">(</span><span class="identifier-syntax">KIND_CHECKING</span><span class="plain-syntax">, </span><span class="string-syntax">"Interpreting equality test of kinds %u, %u\n"</span><span class="plain-syntax">, </span><span class="identifier-syntax">left</span><span class="plain-syntax">, </span><span class="identifier-syntax">right</span><span class="plain-syntax">);</span>
|
|
|
|
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> ((</span><span class="identifier-syntax">Kinds::eq</span><span class="plain-syntax">(</span><span class="identifier-syntax">left</span><span class="plain-syntax">, </span><span class="identifier-syntax">K_truth_state</span><span class="plain-syntax">)) || (</span><span class="identifier-syntax">Kinds::eq</span><span class="plain-syntax">(</span><span class="identifier-syntax">right</span><span class="plain-syntax">, </span><span class="identifier-syntax">K_truth_state</span><span class="plain-syntax">)))</span>
|
|
<span class="plain-syntax"> </span><span class="reserved-syntax">return</span><span class="plain-syntax"> </span><span class="identifier-syntax">I</span><span class="string-syntax">"(*1 && true) == (*2 && true)"</span><span class="plain-syntax">;</span>
|
|
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">kind_constructor</span><span class="plain-syntax"> *</span><span class="identifier-syntax">L</span><span class="plain-syntax"> = </span><span class="identifier-syntax">NULL</span><span class="plain-syntax">, *</span><span class="identifier-syntax">R</span><span class="plain-syntax"> = </span><span class="identifier-syntax">NULL</span><span class="plain-syntax">;</span>
|
|
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> ((</span><span class="identifier-syntax">left</span><span class="plain-syntax">) && (</span><span class="identifier-syntax">right</span><span class="plain-syntax">)) { </span><span class="identifier-syntax">L</span><span class="plain-syntax"> = </span><span class="identifier-syntax">left</span><span class="plain-syntax">-></span><span class="identifier-syntax">construct</span><span class="plain-syntax">; </span><span class="identifier-syntax">R</span><span class="plain-syntax"> = </span><span class="identifier-syntax">right</span><span class="plain-syntax">-></span><span class="identifier-syntax">construct</span><span class="plain-syntax">; }</span>
|
|
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">kind_constructor_comparison_schema</span><span class="plain-syntax"> *</span><span class="identifier-syntax">dtcs</span><span class="plain-syntax">;</span>
|
|
<span class="plain-syntax"> </span><span class="reserved-syntax">for</span><span class="plain-syntax"> (</span><span class="identifier-syntax">dtcs</span><span class="plain-syntax"> = </span><span class="identifier-syntax">L</span><span class="plain-syntax">-></span><span class="identifier-syntax">first_comparison_schema</span><span class="plain-syntax">; </span><span class="identifier-syntax">dtcs</span><span class="plain-syntax">; </span><span class="identifier-syntax">dtcs</span><span class="plain-syntax"> = </span><span class="identifier-syntax">dtcs</span><span class="plain-syntax">-></span><span class="identifier-syntax">next_comparison_schema</span><span class="plain-syntax">) {</span>
|
|
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">Str::len</span><span class="plain-syntax">(</span><span class="identifier-syntax">dtcs</span><span class="plain-syntax">-></span><span class="identifier-syntax">comparator_unparsed</span><span class="plain-syntax">) > </span><span class="constant-syntax">0</span><span class="plain-syntax">) {</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">dtcs</span><span class="plain-syntax">-></span><span class="identifier-syntax">comparator</span><span class="plain-syntax"> = </span><span class="identifier-syntax">KindConstructors::parse</span><span class="plain-syntax">(</span><span class="identifier-syntax">dtcs</span><span class="plain-syntax">-></span><span class="identifier-syntax">comparator_unparsed</span><span class="plain-syntax">);</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">Str::clear</span><span class="plain-syntax">(</span><span class="identifier-syntax">dtcs</span><span class="plain-syntax">-></span><span class="identifier-syntax">comparator_unparsed</span><span class="plain-syntax">);</span>
|
|
<span class="plain-syntax"> }</span>
|
|
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">R</span><span class="plain-syntax"> == </span><span class="identifier-syntax">dtcs</span><span class="plain-syntax">-></span><span class="identifier-syntax">comparator</span><span class="plain-syntax">) </span><span class="reserved-syntax">return</span><span class="plain-syntax"> </span><span class="identifier-syntax">dtcs</span><span class="plain-syntax">-></span><span class="identifier-syntax">comparison_schema</span><span class="plain-syntax">;</span>
|
|
<span class="plain-syntax"> }</span>
|
|
|
|
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">KindConstructors::uses_block_values</span><span class="plain-syntax">(</span><span class="identifier-syntax">L</span><span class="plain-syntax">)) {</span>
|
|
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">KindConstructors::allow_word_as_pointer</span><span class="plain-syntax">(</span><span class="identifier-syntax">L</span><span class="plain-syntax">, </span><span class="identifier-syntax">R</span><span class="plain-syntax">)) {</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">local_block_value</span><span class="plain-syntax"> *</span><span class="identifier-syntax">pall</span><span class="plain-syntax"> =</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">Frames::allocate_local_block_value</span><span class="plain-syntax">(</span><span class="identifier-syntax">Kinds::base_construction</span><span class="plain-syntax">(</span><span class="identifier-syntax">L</span><span class="plain-syntax">));</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">text_stream</span><span class="plain-syntax"> *</span><span class="identifier-syntax">promotion</span><span class="plain-syntax"> = </span><span class="identifier-syntax">Str::new</span><span class="plain-syntax">();</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">WRITE_TO</span><span class="plain-syntax">(</span><span class="identifier-syntax">promotion</span><span class="plain-syntax">, </span><span class="string-syntax">"*=-ComparePV(*1, CastPV(%S, *#2, *2))==0"</span><span class="plain-syntax">,</span>
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">pall</span><span class="plain-syntax">-></span><span class="identifier-syntax">to_refer</span><span class="plain-syntax">-></span><span class="identifier-syntax">prototype</span><span class="plain-syntax">);</span>
|
|
<span class="plain-syntax"> </span><span class="reserved-syntax">return</span><span class="plain-syntax"> </span><span class="identifier-syntax">promotion</span><span class="plain-syntax">;</span>
|
|
<span class="plain-syntax"> }</span>
|
|
<span class="plain-syntax"> }</span>
|
|
|
|
<span class="plain-syntax"> </span><span class="identifier-syntax">text_stream</span><span class="plain-syntax"> *</span><span class="identifier-syntax">cr</span><span class="plain-syntax"> = </span><span class="identifier-syntax">Kinds::Behaviour::get_comparison_routine</span><span class="plain-syntax">(</span><span class="identifier-syntax">left</span><span class="plain-syntax">);</span>
|
|
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> ((</span><span class="identifier-syntax">Str::len</span><span class="plain-syntax">(</span><span class="identifier-syntax">cr</span><span class="plain-syntax">) == </span><span class="constant-syntax">0</span><span class="plain-syntax">) ||</span>
|
|
<span class="plain-syntax"> (</span><span class="identifier-syntax">Str::eq_wide_string</span><span class="plain-syntax">(</span><span class="identifier-syntax">cr</span><span class="plain-syntax">, </span><span class="identifier-syntax">U</span><span class="string-syntax">"signed"</span><span class="plain-syntax">)) ||</span>
|
|
<span class="plain-syntax"> (</span><span class="identifier-syntax">Str::eq_wide_string</span><span class="plain-syntax">(</span><span class="identifier-syntax">cr</span><span class="plain-syntax">, </span><span class="identifier-syntax">U</span><span class="string-syntax">"UnsignedCompare"</span><span class="plain-syntax">))) </span><span class="reserved-syntax">return</span><span class="plain-syntax"> </span><span class="identifier-syntax">I</span><span class="string-syntax">"*=-*1 == *2"</span><span class="plain-syntax">;</span>
|
|
<span class="plain-syntax"> </span><span class="reserved-syntax">return</span><span class="plain-syntax"> </span><span class="identifier-syntax">I</span><span class="string-syntax">"*=- *_1(*1, *2) == 0"</span><span class="plain-syntax">;</span>
|
|
<span class="plain-syntax">}</span>
|
|
</pre>
|
|
<nav role="progress"><div class="progresscontainer">
|
|
<ul class="progressbar"><li class="progressprev"><a href="2-dv.html">❮</a></li><li class="progresschapter"><a href="P-wtmd.html">P</a></li><li class="progresschapter"><a href="1-rm.html">1</a></li><li class="progresscurrentchapter">2</li><li class="progresssection"><a href="2-hrr.html">hrr</a></li><li class="progresssection"><a href="2-ni.html">ni</a></li><li class="progresssection"><a href="2-cu.html">cu</a></li><li class="progresssection"><a href="2-emt.html">emt</a></li><li class="progresssection"><a href="2-ec.html">ec</a></li><li class="progresssection"><a href="2-ea.html">ea</a></li><li class="progresssection"><a href="2-int.html">int</a></li><li class="progresssection"><a href="2-sv.html">sv</a></li><li class="progresssection"><a href="2-th.html">th</a></li><li class="progresssection"><a href="2-dv.html">dv</a></li><li class="progresscurrent">es</li><li class="progresssection"><a href="2-ic.html">ic</a></li><li class="progresssection"><a href="2-kd.html">kd</a></li><li class="progresssection"><a href="2-sc.html">sc</a></li><li class="progresssection"><a href="2-hnae.html">hnae</a></li><li class="progresssection"><a href="2-sn.html">sn</a></li><li class="progresssection"><a href="2-gpr.html">gpr</a></li><li class="progresssection"><a href="2-ie.html">ie</a></li><li class="progresschapter"><a href="3-gm.html">3</a></li><li class="progresschapter"><a href="4-enc.html">4</a></li><li class="progresschapter"><a href="5-act.html">5</a></li><li class="progresschapter"><a href="6-bd.html">6</a></li><li class="progresschapter"><a href="7-cg.html">7</a></li><li class="progressnext"><a href="2-ic.html">❯</a></li></ul></div>
|
|
</nav><!--End of weave-->
|
|
|
|
</main>
|
|
</body>
|
|
</html>
|
|
|