doc(style): update C++ style guide

doc/style.md

@@ -157,30 +157,61 @@ Similarly, we write `x < y + 1` instead of `x<y+1`.
 Google's C++ Style Guide
 ------------------------
 
-We are using a modified version of
+We are using a modified version of [Google's C++ Style Guide][google-style]. 
-[Google's C++ Style Guide][google-style]. Here is a list of checks
+We also have our version of Google's style checker [cpplint.py][cpplint].
-that we *disabled*:
+You can run the checker over the codebase by typing:
 
- - Namespace should be terminated with "namespace"  [readability/namespace]
+    make style
+    
+If you use Ninja, you can check by ``ninja style``. It is also a part of testcases and can be run by 
+
+    ctest -R style_check
+
+*Disabled* Features:
+
+ - Namespace should be terminated with "namespace"
  - At least two spaces is best between code and comments
  - Do not use ``dynamic_cast<>``.  If you need to cast within a class
    hierarchy, use ``static_cast<>`` to upcast.  Google doesn't support
    RTTI.
- - "public:" should be preceded by a blank line  [whitespace/blank_line]
+ - "public:" should be preceded by a blank line
- - Missing space before ``{``  [whitespace/braces]
+ - Missing space before ``{``
  - Found C system header after C++ system header. Should be:
-   environment.h, c system, c++ system, other.  [build/include_order]
+   environment.h, c system, c++ system, other.
-   [4]
  - Labels should always be indented at least one space.  If this is
    a member-initializer list in a constructor or the base class list in
    a class definition, the colon should be on the following line.
-   [whitespace/labels]
+ - You don't need a ``;`` after a ``}``
- - You don't need a ``;`` after a ``}``  [readability/braces]
  - No ``#ifndef`` header guard found
  - Streams are highly discouraged.
- - Extra space before ``(`` in function call  [whitespace/parens]
+ - Extra space before ``(`` in function call
- - Else clause should never be on same line as else [whitespace/newline]
+ - Else clause should never be on same line as else
- - Extra space before ``)``  [whitespace/parens]
+ - Extra space before ``)``
- - Is this a non-const reference? If so, make const or use a pointer. [runtime/references]
+ - Is this a non-const reference? If so, make const or use a pointer.
+ - All parameters should be named in a function
+
+Modified Features:
+
+  - Add ``#include <list>`` for ``list<>``
+
+    => *Check* ``std::list`` instead of ``list`` because we do have our own ``lean::list`` type.
+
+  - Add ``#include <algorithm>`` for copy
+
+    => *Check* ``std::copy`` instead of ``copy`` because we do have our own ``lean::copy`` method.
+
+  - Do not use namespace using-directives. Use using-declarations instead.
+
+    => *Allow* this if filename contains "tests/"
+
+  - Small and focused functions are preferred: foo()
+    has xxx non-comment lines (error triggered by exceeding 500 lines).
+
+    => *Allow* this if filename contains "tests/"
+
+  - Include the directory when naming .h files
+  
+    => *Allow* this if the included filename is "version.h" which is generated by cmake.
 
 [google-style]: http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml
+[cpplint]: /src/cmake/Modules/cpplint.py