Thanks for your elaborate answer, I very much appreciate it. After these discussions, Swift sounds like adopting the best of the worlds of fast and dangerous (C, C++, Fortran), slow and easy (Python, Ruby) and slow and safe (Haskell) languages (I'm listing the extreme examples here from my perspective rather than the actual influences to Swift). I especially like the 'safe by default - unsafe optional' stance, since this gives you the ability to create a working program quickly, but still optimise it later through introducing unsafe behaviour. This can allow Swift to be used for HPC purposes further down the road (provided [1] substantial parts will get Open Sourced, [2] it gets implemented on Linux and [3] it gets support for parallel computing both on node, core and accelerator level). Without having worked with it yet, here's what I'd love to get in order to use it for HPC:
-UnsafeButWarn compiler options -> replaces safe versions of arithmetic / arrays with unsafe ones, but issue runtime warnings whenever unsafe behaviour has occurred. Meant for debugging the runtime into never going unsafe, such that checks can be disabled.
-Unsafe compiler option -> replaces safe operations with unsafe ones. Meant for the production version that has been extensively tested but needs to run as fast as possible.
-UnsafeButWarn compiler options -> replaces safe versions of arithmetic / arrays with unsafe ones, but issue runtime warnings whenever unsafe behaviour has occurred. Meant for debugging the runtime into never going unsafe, such that checks can be disabled.
-Unsafe compiler option -> replaces safe operations with unsafe ones. Meant for the production version that has been extensively tested but needs to run as fast as possible.