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preliminary set support

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[SVN r15908]
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Paul Mensonides
2002-10-13 05:47:23 +00:00
parent b2bd498a4f
commit 33daabd87d
77 changed files with 2878 additions and 208 deletions
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<html>
<head>
<title>sets.html</title>
<link rel="stylesheet" type="text/css" href="../styles.css">
</head>
<body>
<h4>Sets</h4>
<div>
A <i>set</i> is a group of adjacent parenthesized elements.
For example,
</div>
<div class="code">
(<i>a</i>)(<i>b</i>)(<i>c</i>)
</div>
<div>
...is a <i>set</i> of <i>3</i> elements--<i>a</i>, <i>b</i>, and <i>c</i>.
</div>
<div>
<i>Sets</i> are data structures that merge the properties of both <i>lists</i> and <i>tuples</i>
with the exception that <i>sets</i> cannot be empty.&nbsp;
Therefore, an "empty" <i>set</i> is considered a special case scenario that must be handled separately in C++.
</div>
<div class="code"><pre>
#define SET (x)(y)(z)
#define REVERSE(s, state, elem) (elem) state
// append to head ^
BOOST_PP_SET_FOLD_LEFT(REVERSE, BOOST_PP_EMPTY, SET)()
// #1 #2
// 1) placeholder for "empty" set
// 2) remove placeholder
#define SET_B (1)(2)(3)
#define INC(s, state, elem) state (BOOST_PP_INC(elem))
// append to tail ^
BOOST_PP_SET_FOLD_RIGHT(INC, BOOST_PP_SET_NIL, SET)
// ^
// special placeholder that will be "eaten"
// by appending to the tail
</pre></div>
<div>
<i>Sets</i> are extremely efficient.&nbsp;
Element access speed approaches random access--even with <i>sets</i> of up to <i>256</i> elements.&nbsp;
This is because element access (among other things) is implemented iteratively rather than recursively.&nbsp;
Therefore, elements can be accessed at extremely high indices even on preprocessors with low maximum expansion depths.
</div>
<div>
Elements of a <i>set</i> can be extracted with
<b>BOOST_PP_SET_ELEM</b>.
</div>
<h4>Primitives</h4>
<ul>
<li><a href="../ref/set_elem.html">BOOST_PP_SET_ELEM</a></li>
</ul>
</body>
</html>