# If a matrix is written with a double bar instead of square brackets, is there any significance?

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

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I think your interpretation of the notation is correct. Single bars, on the other hand, seem to denote a determinant. –  Dylan Moreland Oct 10 '11 at 13:21
Yes, it's a matrix (he uses double bars where most other people would use parentheses or brackets). Look at the definition here. –  Ｊ. Ｍ. Oct 10 '11 at 13:25