Shilov's Linear Algebra writes a matrix with two bars on each side rather than square brackets. I didn't find any mention of it with a quick Google search, and I can't see any other examples this double bar notation.
Does it mean something other than a matrix? Is it an older notation? Or is it something else?
Thank you
Best Answer
It looks like he means a matrix when he uses double bars:
He uses the standard notation for a determinant, i.e. single bars:
I don't know if his notation for matrices was something that was common at the time he wrote the book, but I don't think it's popular now.