Question about return type for Typescript

[crystalfp]

I just started using the library in my Nodejs+Typescript project with great satisfaction.
But I don't understand the return typing of some functions.
For an example of what I need, inv routine is perfect:

const a = [[1,2], [3,4]];
const b = inv(a) // Type of b is number[][]

Instead I have problems with cross (below is just an example):

const a = [1,2];
const b = [3,4];
const c = cross(a, b);
const len = Math.hypot(...c); // Typescript complains "Type 'MathCollection<MathNumericType>' must have a '[Symbol.iterator]()' method that returns an iterator.ts(2488)"

So I'm forced to put as number[] after cross() or accessing the results of eigs.
What I'm doing wrong here? Or there is a reason cross is not defined as cross<T>(T: a, T: b): T ?
Yes, I tried wit config, but nothing changes.
Thanks for clarifying!
mario

[josdejong]

The TypeScript definitions are hand-written. Some of them are a bit generic and can be refined.

I think we simply need to improve the type definition of function cross. Anyone able to help out here?