Double-pendulum-model-in-Cpp.md

+<table>
+  <tr>
+    <th colspan="2">Double pendulum model in C++</th>
+  </tr>
+  <tr>
+    <td style="text-align:center"><img src="Double-pendulum-model-in-C++_screenshot1.png" width=100%></td>
+    <td style="text-align:center"><img src="Double-pendulum-model-in-C++_screenshot2.png" width=100%></td>
+  </tr>
+  <tr>
+    <th colspan="2">Browse <a href="https://gitlab.onelab.info/doc/tutorials/tree/master/PendulumC++/">model files</a></th>
+  </tr>
+</table>
+
+## Quick start
+
+To run the model, first compile `pend.cpp` with a C++ compiler to create an
+executable `pend.exe`, e.g. with
+
+```
+c++ pend.cpp -o pend.exe
+```
+
+Them open `pend.exe` with Gmsh and click on the "Run" button in the left panel.
+
+## Features addressed in this tutorial
+
+  * C++ ONELAB model
+
+## Additional information
+
+Any C++ code can become a native ONELAB client by including the
+[`onelab.h`](https://gitlab.onelab.info/gmsh/gmsh/tree/master/Common/onelab.h)
+and header (which depends on
+[`GmshSocket.h`](https://gitlab.onelab.info/gmsh/gmsh/tree/master/Common/GmshSocket.h)).
+
+----
+*Model developed by @henrotte and @geuzaine.*