As a casual Swift desktop developer, I also wonder about how practical and fast Swift is, especially when compared to scripting languages like Python.

For instance, last week, I was working on bit manipulation and realized that Swift has methods to count 1 and 0 bits:

let value: UInt8 = 0b11010101

let count = value.nonzeroBitCount

It's fast enough to make running an app feel like running a native app – faster start time, less memory used, less power hungry, more responsive UI – compared to browser based cross-platform apps.

One can say it achieves maximum user interaction speed.

For most critical calculations, one can easily integrate C++/C libraries – at the source code level – which Swift can compile, link and call directly.

Or drop down to unsafe features of Swift and achieve speeds comparable to C++. But that's not really needed in most of real life use cases. Convenience is what really matters when it comes to Swift.

What's wrong with that? This is often a single CPU instruction and a lot of languages have support for it, including python

https://en.m.wikipedia.org/wiki/Hamming_weight