"In computer programs, concerns for efficiency may limit the possible ways to achieve a particular function, making a particular expression necessary to achieving the idea. In this case, the expression is not protected by copyright."
"Finally, material that exists in the public domain can not be copyrighted and is also removed from the analysis."
That code is specifically optimized for efficiency and there were similar approaches floating (get it?) around in the 1980s.
The magic-constant is not optimal there exist better alternatives. It is not necessary to implement this function and should be copyrightable. It is also not a trivial part.
On the other hand, Microsoft may only need to show "Hey, we got this code from FooBar under this license and this license and ..."
Why should it be copyrightable. It's just a way to calculte inverse square root. This falls under the public, in my non lawyer opinion. Such small snippets do not qualify, usually, for copyright.
It's not just the constant but it was easiest to identify for me in the last post. And due to it's popularity the size of the snippet doesn't matter, it stands on its own as a significant work.
The essence of the algorithm takes 4 lines: function declaration, declaration of 'y', one line for calculating the exponent in log-space, one line for returning the root finding.
The rest is fluff. Every line of the snippet has creative input with the chosen names ('threehalfs' for 1.5F), the order of declarations and instructions, the redundancy. There have been internet-wars around indentations and newlines, these are style choices.
((And it is public -- GPL more specifically, which is a restrictive license that should be respected. I think this snippets makes a perfect example of the dangers of copilot. But not one to litigate details with.))
(((Thinking back, I'm not sure anymore how the license laundering argument works if they got the code from a fair-use MIT-licensed hobby project. Can one person claim fair-use and include it under an MIT-license and have somebody else say 'oh this free code I'm going to use it commercially'?)))
https://en.wikipedia.org/wiki/Abstraction-Filtration-Compari...
"In computer programs, concerns for efficiency may limit the possible ways to achieve a particular function, making a particular expression necessary to achieving the idea. In this case, the expression is not protected by copyright."
"Finally, material that exists in the public domain can not be copyrighted and is also removed from the analysis."
That code is specifically optimized for efficiency and there were similar approaches floating (get it?) around in the 1980s.