Why a single paren in vector norm notation?

Question

I am reading Goodfellow-Bengio-Courville Deep Learning book, and right at the beginning (chapter 1, where they go over basic Linear algebra concepts) they use this notation to define a vector norm:

$$ \| x\|_p = \left. \sum_i |x_i|^p \right)^{1/p} $$

the meaning is clear, and the notation is what I would have expected, except for the single closing parenthesis. Any special meaning? I am not familiar with this convention.

Answer 1

To my knowledge, there's no special meaning to the unmatched closed parenthesis there.

For some reason, you are not seeing the open parenthesis,

but it is there in this online version on page 37, equation 2.30.

Answer 2

An opening parenthesis has definitely been omitted in a typo. This formula is the standard definition of the $L^p$ norm; even the left-hand side is its usual symbol.