A simple test of interfacing C with Swift code. This trivial example only exposes 1 C function from thing.c via thing.h which is #include'ed in the Xcode created bridging header. After including thing.h in the bridging header, items are automagically available in Swift.
The app has 2 buttons which execute algorithmically identical functions, one written in Swift and one in C. The C code runs considerably faster than the Swift equivalent in debug mode. In release mode, they both execute at a similar speed.