Comment by Razengan

That's human error. "Correctness vs. mistakes" applies to all human languages too, English etc.

In math, `a - b` doesn't occasionally become `b - a` if one CPU/thread/stream finishes before an other, just to give one example.

Or, if you write `1 + 2` it will forever be `1 + 2`, unlike code where it may become `3 / 4 - 5 + 6 ^ 7 + 1 + 2` or whatever junk gets appended before or after your expression tomorrow (analogy for the OS/environment your code runs in)

I guess to put it simply: code is affected by its environment, math isn't.