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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
<html lang="en">
 <head>
  <title>
   Autoconf Macro: ac_cxx_use_numtrait
  </title>
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 </head>
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      M4 Source</a>
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  <hr>
  <h1>
   ac_cxx_use_numtrait
  </h1>
  <h2>
   Synopsis
  </h2>
  <p class="indent" style="white-space:nowrap;">
   <code>AC_CXX_USE_NUMTRAIT</code>
  </p>
  <h2>
   Description
  </h2>
  <div class="indent">
   <p>
    If the compiler supports numeric traits promotions, define
    HAVE_USE_NUMTRAIT.
   </p>
  </div>
  <h2>
   Author
  </h2>
  <p class="indent">
   Todd Veldhuizen, Luc Maisonobe &lt;luc@spaceroots.org&gt;
  </p>
  <h2>
   Last Modified
  </h2>
  <p class="indent">
   2004-02-04
  </p>
  <h2>
   M4 Source Code
  </h2>
  <div class="indent">
   <pre class="m4source">
AC_DEFUN([AC_CXX_USE_NUMTRAIT],
[AC_CACHE_CHECK(whether the compiler supports numeric traits promotions,
ac_cv_cxx_use_numtrait,
[AC_REQUIRE([AC_CXX_TYPENAME])
 AC_LANG_SAVE
 AC_LANG_CPLUSPLUS
 AC_TRY_COMPILE([
#ifndef HAVE_TYPENAME
 #define typename
#endif
template&lt;class T_numtype&gt; class SumType       { public : typedef T_numtype T_sumtype;   };
template&lt;&gt;                class SumType&lt;char&gt; { public : typedef int T_sumtype; };
template&lt;class T&gt; class A {};
template&lt;class T&gt; A&lt;typename SumType&lt;T&gt;::T_sumtype&gt; sum(A&lt;T&gt;)
{ return A&lt;typename SumType&lt;T&gt;::T_sumtype&gt;(); }
],[A&lt;float&gt; x; sum(x); return 0;],
 ac_cv_cxx_use_numtrait=yes, ac_cv_cxx_use_numtrait=no)
 AC_LANG_RESTORE
])
if test "$ac_cv_cxx_use_numtrait" = yes; then
  AC_DEFINE(HAVE_USE_NUMTRAIT,,[define if the compiler supports numeric traits promotions])
fi
])
</pre>
  </div>
 </body>
</html>