Update CONTRIBUTING.md

CONTRIBUTING.md

@@ -119,8 +119,9 @@ Implementation details are put into a subnamespace `Impl`. A few more subnamespa
 of `AMDiS` are allowed, e.g., `Concepts`. If one of these subnamespaces need another
 subsubnamespace for implementation details, it should be named `Impl_`.
 
-## Line length
+## Formatting
 
+### Line length
 Each line of text in your code should be at most 100 characters long.
 
 **Exceptions:**
@@ -128,9 +129,49 @@ Each line of text in your code should be at most 100 characters long.
 * A raw-string literal may have content that exceeds 100 characters.
 * ...
 
-## Indentation
+### Indentation
+Use two spaces instead of tabs! Follow the formatting rules of the K&R style.
 
-Use two spaces instead of tabs!
+### Variable qualifiers
+Use trailing `const`/`volatile` qualifiers for variables, e.g.
+
+```c++
+double const& d_ref = d;
+```
+
+### Functions
+Try to put all parameters in the line of the function declaration until it exceeds
+the maximum line length. Then list remaining arguments aligned with the first 
+function argument.  Follow the style of the brackets, like
+
+```c++
+return_type function_name(Arg1 arg1, LongArgumentType longArgumentName,
+                          Arg3 argument3)
+{
+  // implementation of the function
+}
+```
+
+### Classes
+Put base-classes on a new line, do not indent labels, member variables are appended
+with an underscore and follow the other formatting rules in the followign example:
+
+```c++
+template <class Type>
+class SubClass
+    : public BaseClass
+{
+public:
+  SubClass(Arg1 arg1, Arg2 arg2)
+    : member1_(arg1)
+    , member2_(arg2)
+  {}
+  
+private:
+  Arg1 member1_;
+  Arg2 member2_;
+};
+```
 
 ## Documentation