newRPL - build 1255 released! [updated to 1299]

[The Shadow]

I've been thinking some more about equations involving matrices.

Many headaches arise when the matrices aren't square. There's whole classes of things you can't do to them that you can to square ones: inversion and raising to a power, among others. (Though a "pseudo-inverse" can be defined for all matrices, whether rectangular or non-singular, and might be worth implementing.)

But worse yet, there's *three* versions of the identity matrix you'd need for interacting with scalars: one for multiplying from the left, one for multiplying from the right, and one used for addition.

Does anyone actually use non-square matrices in equations? The only examples that are immediately coming to mind are ones in which they're multiplied by their transpose to make them square first.

Any new news, Claudio?