mathtools brackets larger than \Bigg

Question

I'd like to use the syntax of the mathtools package to generate brackets larger than \Bigg.

One can create larger brackets than \Bigg of specified size using

About big parenthesis larger than Bigg

However, that solution doesn't work with the \DeclarePairedDelimiter construct of mathtools.

See the MWE below. I suspect that what's needed is \Vastl, \Vastr, and \Vastm commands.

\documentclass{article}


\usepackage{mathtools}
\makeatletter
\newcommand{\vast}{\bBigg@{4}}
\newcommand{\Vast}{\bBigg@{5}}
\makeatother

\DeclarePairedDelimiter{\parens}()

\begin{document}

\[
 \parens[\Bigg]{\dfrac{\dfrac{y}{x}}{\dfrac{a}{b}}}
\]

\[
 \Vast({\dfrac{\dfrac{y}{x}}{\dfrac{a}{b}}} \Vast)\qquad
 \parens[\Vast]{\dfrac{\dfrac{y}{x}}{\dfrac{a}{b}}}  % does not work
\]
\end{document}

Answer 1

Yes, your suspicion is right. Simply define:

\newcommand{\vastl}{\mathopen\vast}
\newcommand{\vastm}{\mathrel\vast}
\newcommand{\vastr}{\mathclose\vast}
\newcommand{\Vastl}{\mathopen\Vast}
\newcommand{\Vastm}{\mathrel\Vast}
\newcommand{\Vastr}{\mathclose\Vast}

and you can use \vast and \Vast with \DeclarePairedDelimiter.

MWE:

\documentclass{article}


\usepackage{mathtools}
\makeatletter
\newcommand{\vast}{\bBigg@{4}}
\newcommand{\Vast}{\bBigg@{5}}
\newcommand{\vastl}{\mathopen\vast}
\newcommand{\vastm}{\mathrel\vast}
\newcommand{\vastr}{\mathclose\vast}
\newcommand{\Vastl}{\mathopen\Vast}
\newcommand{\Vastm}{\mathrel\Vast}
\newcommand{\Vastr}{\mathclose\Vast}
\makeatother

\DeclarePairedDelimiter{\parens}()

\begin{document}

\[
 \parens[\Bigg]{\dfrac{\dfrac{y}{x}}{\dfrac{a}{b}}}
\]

\[
 \Vast({\dfrac{\dfrac{y}{x}}{\dfrac{a}{b}}} \Vast)\qquad
 \parens[\Vast]{\dfrac{\dfrac{y}{x}}{\dfrac{a}{b}}}  % works now
\]
\end{document} 

Output: