| <?xml version="1.0" encoding="UTF-8" standalone="no"?> |
| <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Interacting with C</title><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><meta name="keywords" content="ISO C++, library" /><meta name="keywords" content="ISO C++, runtime, library" /><link rel="home" href="../index.html" title="The GNU C++ Library" /><link rel="up" href="numerics.html" title="Chapter 12. Numerics" /><link rel="prev" href="generalized_numeric_operations.html" title="Generalized Operations" /><link rel="next" href="io.html" title="Chapter 13. Input and Output" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Interacting with C</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="generalized_numeric_operations.html">Prev</a> </td><th width="60%" align="center">Chapter 12. |
| Numerics |
| |
| </th><td width="20%" align="right"> <a accesskey="n" href="io.html">Next</a></td></tr></table><hr /></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="std.numerics.c"></a>Interacting with C</h2></div></div></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="numerics.c.array"></a>Numerics vs. Arrays</h3></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 class="section"><div class="titlepage"><div><div><h3 class="title"><a id="numerics.c.c99"></a>C99</h3></div></div></div><p>In addition to the other topics on this page, we'll note here some |
| of the C99 features that appear in libstdc++. |
| </p><p>The C99 features depend on the <code class="code">--enable-c99</code> configure flag. |
| This flag is already on by default, but it can be disabled by the |
| user. Also, the configuration machinery will disable it if the |
| necessary support for C99 (e.g., header files) cannot be found. |
| </p><p>As of GCC 3.0, C99 support includes classification functions |
| such as <code class="code">isnormal</code>, <code class="code">isgreater</code>, |
| <code class="code">isnan</code>, etc. |
| The functions used for 'long long' support such as <code class="code">strtoll</code> |
| are supported, as is the <code class="code">lldiv_t</code> typedef. Also supported |
| are the wide character functions using 'long long', like |
| <code class="code">wcstoll</code>. |
| </p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="generalized_numeric_operations.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="io.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Generalized Operations </td><td width="20%" align="center"><a accesskey="h" href="../index.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 13. |
| Input and Output |
| |
| </td></tr></table></div></body></html> |
