I was wondering about an efficient way to generate an inner product symbol like

```
\[
\langle\langle u, v \rangle\rangle
\]
```

(i.e., double angle brackets), or a norm symbol like

```
\[
\lvert\lVert x \rVert\rvert
\]
```

(i.e., triple bars). Of course, the above examples are terrible, no respect for spaces. Is there an efficient way of doing this so that the delimiters are extensible (compatible with `$\left$`

and `$\right$`

)?

I know of the package *nath*, but it's quite incompatible with amsmath, and generates thousands of errors, so is not an option. I've also tried with "DeclareMathDelimiterX" in *mathmode*, but couldn't get it to work quite as well as I'ld like.

## Best Answer

Strangely enough, Detexify didn't help here. Another great source is The Comprehensive LaTeX Symbol List, and this has the following answers:

For your first delimiter pair use

`\llangle`

and`\rrangle`

from the`mnsymbol`

package (as observed in Martin's comment above); for the second pair you can try`\vvvert`

from`mathabx`

.