Zebedee Mason discusses in his recent article some GOF idioms and analyzes them with his tool DeepsEnds.
by Zebedee Mason
From the article:
The example C++ code from the GoF (Gang of Four) book Design Patterns has had its dependencies analysed with DeepEnds. Certain examples have been refactored to remove circular dependencies enabled by pre-declaration of classes. These cycles in the graph serve to reduce the ability to subsequently modify the code with ease.