C-Interoperability-and-Type-Casting.md

+<p><strong>Avoid mixing C headers, functions, and casting if there is a corresponding C++ equivalent</strong></p><ol><li><strong>C Header/Function:</strong> use C++ equivalents. Use  cmath  not math.h,  iostream  not stdio.h  <ul><li><code>Don't</code> Use C header/functions<ul><li><pre style="border: 0;"><code>#include &lt;math.h&gt;
+#include &lt;stdio.h&gt;
+...
+float  powerOfTwo = powf( 2.f, 5.f );
+printf ( &quot;2^5 = %f\n&quot;, powerOfTwo );</code></pre></li></ul></li><li><code>Do</code> Use C++ header/functions<ul><li><pre style="border: 0;"><code>#include &lt; cmath &gt;
+#include &lt; iostream &gt;
+...
+constexpr float  powerOfTwo =  std::pow ( 2., 5. );
+std::cout  &lt;&lt; &quot;2^5 = &quot; &lt;&lt; powerOfTwo &lt;&lt; &quot;\n&quot;;
+</code></pre></li></ul></li></ul></li>
+
+<li><strong>Use C headers/functions when:</strong>
+<ul><li>There is no C++ equivalent
+<ul><li>C++ API is deprecated or not fully supported libraries ( <em>e.g.</em> MPI, CUDA_C, PETSc )</li><li>POSIX functionality <em>e.g.</em> unistd.h </li></ul></li><li>Language Interoperability is required
+<ul><li>C++ –&gt; C —&gt; Fortran </li><li>C++ –&gt; C —&gt; JNI —&gt; Java</li></ul></li></ul></li>
+
+<li><strong>Type Casting:</strong> use C++11 style casting: static_cast, dynamic_cast, reinterpret_cast when corresponding instead of ( Type ) C style.<ul><li><code>Don't</code> <ul><li><pre style="border: 0;"><code> ( int ) foo;</code></pre></li></ul></li><li><code>Do</code> 
+<ul><li><pre style="border: 0;"><code>  static_cast&lt;   int   &gt;  ( foo );</code></pre></li></ul></li>
+<ul><li><pre style="border: 0;"><code>  reinterpret_cast&lt;   double*   &gt;  ( foo );</code></pre></li></ul</li>
+</ul></li></ol>