Discussion: namespace vs prefix

[jslee02]

Since #652, DART has been composed as the core library dart and several component libraries like dart-optimizer-nlopt, and the component libraries get compiled only when the required dependencies are installed. We then introduced dart::gui::osg namespace for OpenSceneGraph dependent library rather than using prefix like dart::gui::OsgViewer. However, we still use prefixes for other component classes like NloptSolver and IpoptSolver. I think we should follow one rule for consistency, but not sure which one is preferred way.

After Googling, I learned that using namespaces is the C++ way while using prefixes is the C way, and I'm inclined to using namespaces because of this reason.

Downsides of using namespace I can imagine would be (1) that it would require more typing for :: (e.g., NloptSolver vs nlopt::Solver) and (2) that it could cause namespace conflict with the dependency namespace (e.g., dart::collision::fcl of DART and fcl of FCL). (2) can be resolved by using the global namespace specifier like ::fcl for FCL namespace, though.

Here are some examples of current, namespace, and prefix cases.

current

dart::collision::FCLCollisionDetector
dart::collision::BulletCollisionDetector
dart::collision::DARTCollisionDetector

dart::optimizer::NloptSolver
dart::optimizer::IpoptSolver

dart::gui::GlutWindow
dart::gui::osg::[~]

prefix

dart::collision::FCLCollisionDetector
dart::collision::BulletCollisionDetector
dart::collision::DARTCollisionDetector

dart::optimizer::NloptSolver
dart::optimizer::IpoptSolver

dart::gui::GlutWindow
dart::gui::GlfwWindow
dart::gui::Osg[~]

namespace

dart::collision::fcl::CollisionDetector
dart::collision::bullet::CollisionDetector
dart::collision::dart::CollisionDetector // or something like dart::collision::builtin::CollisionDetector since dart::collision::dart would be ambiguous

dart::optimizer::nlopt::Solver
dart::optimizer::ipopt::Solver

dart::gui::glut::Window
dart::gui::glfw::Window
dart::gui::osg::[~]

[mxgrey]

I think we can close this, since we've settled pretty strongly on using namespaces instead of prefixes.

[jslee02]

I agree on using namespace over prefixes, but we still use prefixes for optimizers and collision detectors. If we close this, then let's create an issue to track it.