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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Chapter 23. Interacting with C</title><meta name="generator" content="DocBook XSL Stylesheets V1.74.0" /><meta name="keywords" content=" ISO C++ , library " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="numerics.html" title="Part X. Numerics" /><link rel="prev" href="bk01pt10ch22.html" title="Chapter 22. Generalized Operations" /><link rel="next" href="bk01pt10ch23s02.html" title="C99" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 23. Interacting with C</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="bk01pt10ch22.html">Prev</a> </td><th width="60%" align="center">Part X. Numerics</th><td width="20%" align="right"> <a accesskey="n" href="bk01pt10ch23s02.html">Next</a></td></tr></table><hr /></div><div class="chapter" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title"><a id="manual.numerics.c"></a>Chapter 23. Interacting with C</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="bk01pt10ch23.html#numerics.c.array">Numerics vs. Arrays</a></span></dt><dt><span class="sect1"><a href="bk01pt10ch23s02.html">C99</a></span></dt></dl></div><div class="sect1" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="numerics.c.array"></a>Numerics vs. Arrays</h2></div></div></div><p>One of the major reasons why FORTRAN can chew through numbers so well
is that it is defined to be free of pointer aliasing, an assumption
that C89 is not allowed to make, and neither is C++98. C99 adds a new
keyword, <code class="code">restrict</code>, to apply to individual pointers. The
C++ solution is contained in the library rather than the language
(although many vendors can be expected to add this to their compilers
as an extension).
</p><p>That library solution is a set of two classes, five template classes,
and "a whole bunch" of functions. The classes are required
to be free of pointer aliasing, so compilers can optimize the
daylights out of them the same way that they have been for FORTRAN.
They are collectively called <code class="code">valarray</code>, although strictly
speaking this is only one of the five template classes, and they are
designed to be familiar to people who have worked with the BLAS
libraries before.
</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="bk01pt10ch22.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="numerics.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="bk01pt10ch23s02.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 22. Generalized Operations </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> C99</td></tr></table></div></body></html>
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