Developer's-corner/Boundary-Conditions.md

@@ -67,6 +67,36 @@ In a carefully chosen source file ([src/D3/boundariesConditions.cpp](https://git
 ```
 You're done.
 
+## Passing parameters
+
+Parameters can be passed from the configuration file to the boundary condition code as a `key->value` map:
+
+```
+Disk {
+ ....
+ Boundaries parrot
+ {
+    type "Norvegian Blue"
+    voltage 25000.0
+    alive false
+ }
+ ....
+}
+```
+
+They will be made available to the code through a [std::map](http://www.cplusplus.com/reference/map/map/):
+
+```
+ void
+ PetChopBC(GasDisk& gas, real dt) {
+    using namespace std;
+    map<string, string> const& params = gas.physic().boundaries.params;
+    real voltage = boost::lexical_cast<real>(attrs["voltage"];
+    bool alive   = boost::lexical_cast<real>(attrs["voltage"];
+    ...
+ }
+```
+
 ## Tips
 
 ### Factorize