Norm with adjustable size?

Question

There was a similar question asked some time back. The solutions was to use the package amsmath and define norm as

\newcommand{\norm}[1]{\left\lVert#1\right\rVert}

However, I am using the packages newpxtext and newpxmath and it is advised not to amsmath with them. How can I then achieve a re-scaled norm sign in LaTeX?

Answer 1

I'd recommend defining them via the mathtools package using

\DeclarePairedDelimiter\norm\lVert\rVert

Then

\norm{x}    =  \lVert x \rVert
\norm*{x}   = \left\lVert x \right\rVert
\norm[\Big] = \Bigl\lVert x \Bigr\rVert

For more information see the mathtools manual

Note that it is generally not recommended to have autoscaling as the default, only use autoscaling in those explicit instances you need it. (I personally use it very rarely in my manuscript edits)

Answer 2

You can do that easily with mathtools (which loads amsmath): adding this code in your preamble:

\DeclarePairedDelimiter{\norm}\lVert\rVert

defines a \norm command and a starred version \norm*, which adds a pair of implicit \left ... \right in front of the delimiters. For fine-tuning the delimiters size, the unstarred version accepts an optional argument: \norm[\big], or [\Big], [\bigg], [\Bigg], which adds a pair of implicit \bigl ... \bigr, &c., in front of the delimiters.