While not really related to the math topic, let me answer this:

- You can add an arbitrary number of trailing `[..]` blocks and they are just trailing arguments. So 2 & 3 are really the same.

- 3 & 4 are different because argument lists may _never_ have a space before them in Typst. you can also not write `calc.min (1, 2)`

The reason why the space may not be added is that you can write

    #for x in range(5) [
        Value is #x
    ]

And `range(5) [..]` therefore needs to be different from `range(5)[..]`. This aligns with normal formatting conventions and I haven't seen this become a problem in practice.