[misc.arrayTools] move Vector to its own submodule, and rewrite as a tuple subclass

[justvanrossum]

I felt our n-dimensional Vector class could be improved by making it a subclass of tuple, and deserves its own module.

This change makes Vector instances immutable. It appears this was the intention, as it did support __getitem__ but not __setitem__.

The internal values attribute is gone. I added a values read-only property for backward compatibility. Setting .values is no longer supported (due to Vector's new immutablity).

I added a two methods:

• vector.length(): an alias for abs(vector)
• vector.normalized(): returns the norm vector

I added some DeprecationWarnings.

[anthrotype]

Thanks!

When I implement Vector class, I like to call what you namedlength() => norm() and what you named normalized() => unit().

But it probably doesn't really matter.

I wonder about the use of abs() as a shortcut to computing the norm/magnitude/length/whathaveyou of the vector. Is that common? I guess it can be handy, but also may surprise a bit (it did surprise me).

[justvanrossum]

When I implement Vector class, I like to call what you named length() => norm()

It seems that "length", "norm" and "magnitude" are all synonyms here. I prefer "length" as it's a word that anyone understands. I just had to google "norm", as I wasn't even sure...

and what you named normalized() => unit().

Right, that makes sense, too. I prefer "normalized" as it implies an action.

I wonder about the use of abs() as a shortcut to computing the norm/magnitude/length/whathaveyou of the vector. Is that common? I guess it can be handy, but also may surprise a bit (it did surprise me).

It surprised me, too, but I took it from the original Vector, so it better stay for b/w compatibility... It makes sense given the |vec| mathematical notation, but this was the first time I saw it used in Python via __abs__.

[anthrotype]

ok, sgtm! thanks

[justvanrossum]

Now it would be nice to use it more in fonttools itself. Many things in bezierTools could benefit from it, like calcCubicParameters().

(Back in the day fonttools used numpy to make these kinds of operations easier to write. I'm very glad Behdad got rid of that dependency, but I've occationally missed the convenience.)