Use \DeclarePairedDelimiter instead of \def to define ceil and floor.

[xuhdev]

Using \DeclarePairedDelimiter offers much more benefit such as auto scaling of the paired operator.
See

https://tex.stackexchange.com/questions/94410/easily-change-behavior-of-declarepaireddelimiter

for some examples.

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Aside from that, I highly suggest adding a license for these files -- no explicit license essentially means propriety. If you like public domain, you can try CC0...

[srush]

Thanks, but could you send the PR to the DL book repo https://github.com/goodfeli/dlbook_notation ?

I would prefer not to change non-breaking issues in this file this year.

Adding a license is a good idea though, thanks.