Can confirm it is a font substitution issue. When I open the PDF a different font is used (note the very distinctive “r”) which has much better (but not great) kerning.

Colorado?

Most mathematicians, engineers, and scientists don’t use the asterisk symbol for multiplication. Most don’t write any symbol as it’s implicit. If they do use a symbol they would use a dot or x symbol (though never an actual x). In mathematics, the asterisk is mostly only used to represent convolutions.

Most common:

abc

Less common:

a • b • c

a × b × c

Never:

a * b * c

While to most people this doesn’t really matter (and should feel free using * for multiplication). It shows someone with minimal formal experience in mathematics using this formula

You can use swift package manager to create an executable target, which you can then run on macOS from the command line. Most frameworks (aside from UI) are shared between iOS and macOS like AVFoundation. If you don’t have access to macOS, you can still use swift package manager to build and run code on Linux or Windows, though you unfortunately won’t have access to any Apple frameworks.