76 lines
3.7 KiB
HTML
76 lines
3.7 KiB
HTML
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<!doctype html public "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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Generated from r6rs.tex by tex2page, v 20100828
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(running on MzScheme 4.2.4, :unix),
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(c) Dorai Sitaram,
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http://evalwhen.com/tex2page/index.html
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-->
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<head>
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<meta http-equiv="content-type" content="text/html; charset=UTF-8">
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<title>
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Revised^6 Report on the Algorithmic Language Scheme
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</title>
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<link rel="stylesheet" type="text/css" href="r6rs-Z-S.css" title=default>
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<meta name=robots content="index,follow">
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</head>
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<body>
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<div id=slidecontent>
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<div align=right class=navigation>[Go to <span><a href="r6rs.html">first</a>, <a href="r6rs-Z-H-4.html">previous</a></span><span>, <a href="r6rs-Z-H-6.html">next</a></span> page<span>; </span><span><a href="r6rs-Z-H-2.html#node_toc_start">contents</a></span><span><span>; </span><a href="r6rs-Z-H-21.html#node_index_start">index</a></span>]</div>
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<p></p>
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<a name="node_chap_2"></a>
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<h1 class=chapter>
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<div class=chapterheading><a href="r6rs-Z-H-2.html#node_toc_node_chap_2">Chapter 2</a></div><br>
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<a href="r6rs-Z-H-2.html#node_toc_node_chap_2">Requirement levels</a></h1>
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<p></p>
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<p>
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The key words “must”, “must not”, “should”,
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“should not”, “recommended”, “may”, and “optional” in this
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report are to be interpreted as described in RFC 2119 [<a href="r6rs-Z-H-21.html#node_bib_3">3</a>].
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Specifically:</p>
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<p>
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</p>
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<dl><dt></dt><dd>
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</dd><dt><b>must</b></dt><dd><a name="node_idx_64"></a>This word means that a statement is an absolute
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requirement of the specification.
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</dd><dt><b>must not</b></dt><dd><a name="node_idx_66"></a>This phrase means that a statement is an absolute
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prohibition of the specification.
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</dd><dt><b>should</b></dt><dd><a name="node_idx_68"></a>This word, or the adjective “recommended”, means that
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valid reasons may exist in particular circumstances to ignore a
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statement, but that the implications must be understood and weighed
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before choosing a different course.
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</dd><dt><b>should not</b></dt><dd><a name="node_idx_70"></a>This phrase, or the phrase “not recommended”, means
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that valid reasons may exist in particular circumstances when the
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behavior of a statement is acceptable, but that the implications
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should be understood and weighed before choosing the course described
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by the statement.
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</dd><dt><b>may</b></dt><dd><a name="node_idx_72"></a>This word, or the adjective “optional”, means that an item
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is truly optional.
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</dd></dl><p></p>
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<p>
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In particular, this report occasionally uses “should” to designate
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circumstances that are outside the specification of this report, but
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cannot be practically detected by an implementation; see
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section <a href="r6rs-Z-H-8.html#node_sec_5.4">5.4</a>. In such circumstances, a
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particular implementation may allow the programmer to ignore the
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recommendation of the report and even exhibit reasonable behavior.
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However, as the report does not specify the behavior,
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these programs may be unportable, that is, their execution might
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produce different results on different implementations.</p>
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<p>
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Moreover, this report occasionally uses the phrase “not required” to note the
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absence of an absolute requirement.</p>
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<p>
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</p>
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<p></p>
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<div class=smallskip></div>
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<p style="margin-top: 0pt; margin-bottom: 0pt">
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<div align=right class=navigation>[Go to <span><a href="r6rs.html">first</a>, <a href="r6rs-Z-H-4.html">previous</a></span><span>, <a href="r6rs-Z-H-6.html">next</a></span> page<span>; </span><span><a href="r6rs-Z-H-2.html#node_toc_start">contents</a></span><span><span>; </span><a href="r6rs-Z-H-21.html#node_index_start">index</a></span>]</div>
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</p>
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<p></p>
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</div>
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</body>
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</html>
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