<::SomeNamespace> doesn't compile in older versions of g++ (<4.8).
Specifically, with g++ 4.7.3, I see
In file included from src/gadgetlib2/adapters.hpp:18:0, from src/gadgetlib2/adapters.cpp:10: src/gadgetlib2/constraint.hpp:157:23: error: ‘<::’ cannot begin a template-argument list [-fpermissive] compilation terminated due to -Wfatal-errors.
Adding a space fixes the problem.
<::SomeNamespace> doesn't compile in older versions of g++ (<4.8).
Specifically, with g++ 4.7.3, I see
In file included from src/gadgetlib2/adapters.hpp:18:0, from src/gadgetlib2/adapters.cpp:10: src/gadgetlib2/constraint.hpp:157:23: error: ‘<::’ cannot begin a template-argument list [-fpermissive] compilation terminated due to -Wfatal-errors.Adding a space fixes the problem.