Developer's-corner/Configuration-Checks.md

 
+### How it works
+
 It's possible to add as many consistency checks as you want in the ConfigLoader class. 
+
+A check is a function those signature is `bool check(boost::property_tree::ptree const&, std::ostream&)`, you can register it through ConfigLoader::addCheck.
+
+When loading the configuration, all registered checks will be called upon the property_ptree. If one check returns `false`, the program will stop.
+
+## example
+
+```
+bool
+CheckReferentialRotation(pt::ptree const& pt, std::ostream& log) {
+      DiskReferentialType type = pt.get<DiskReferentialType>("Disk.Referential.Type");
+  bool pass = true;
+  switch (type) {
+  case DR_COROTATING:
+    if (pt.get_optional<real>("Disk.Referential.Omega")) {
+      log << "Fatal: Can't specify both " << type << " and Omega.\n";
+      pass = false;
+    }
+    break;
+  }
+  return pass;
+}
+
+// register in constructor to activate it by default.
+ConfigLoader::ConfigLoader(std::ostream& log)
+   : myLog(log), myChecks() {
+  ...
+  loader.addCheck(CheckReferentialRotation);
+  ...
+}
+```
+
+
+```