What do the single bars in the Cauchy-Schwarz equation represent?

[zimbabwe]

I need to write out the proof for the Cauchy-Schwarz equation from quantum computing. I'm stuck on the first step as I don't understand what the single bars on the first term in the equation. Double bars is length but single??


http://en.wikipedia.org/wiki/Cauchy–Schwarz_inequality

 

[diazona]

Single bars indicate the absolute value, or magnitude.

For the record, it's not uncommon for people to use single bars to designate the norm (length) of a vector, even though the proper notation is technically double bars.

 

[zimbabwe]

Thanks I was totally stuck, as in all the notes the professor used double bars.