\mathlarger does not make anything larger

Question

I am using VerbTeX on an iPhone. The \mathlarger command in math mode does not actually make anything larger. Text and and symbols within it do not get sized differently. Why?

Commands like \big and \LARGE also have no effect and \scalebox throws an error if I use a command like \| inside the second set of braces following it.

Remember, this is all in math mode (e.g., $...$).

Code:

\documentclass[varwidth=true, border=10pt]{standalone}
\usepackage[utf8]{inputenc}
\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{relsize}
\usepackage{graphicx}
\begin{document}
$\underset{i=0} {\overset{\lfloor l/n \rfloor} {\mathlarger{\|}}}$
\end{document}

Answer 1

I wouldn't use \overset, \underset and \mathlarger for this application.

\documentclass{article}
\usepackage{amsmath}
\usepackage{amssymb}

\makeatletter
\newcommand{\Vertop}{\DOTSB\mathop{\mathpalette\Vertop@\relax}\slimits@}
\newcommand{\Vertop@}[2]{%
  \ifx#1\displaystyle\expandafter\big\fi\|\vphantom{\sum}
}
\makeatother

\begin{document}

$\Vertop_{i=0}^{\lfloor l/n \rfloor} \quad \sum_{i=0}^{\lfloor l/n \rfloor}$

\[
\Vertop_{i=0}^{\lfloor l/n \rfloor} \quad \sum_{i=0}^{\lfloor l/n \rfloor}
\]

\end{document}

Answer 2

\big (or here \Bigg) does make the || larger:

\documentclass[varwidth=true, border=10pt]{standalone}
%\usepackage[utf8]{inputenc}
\usepackage{amssymb}
\usepackage{amsmath}
%\usepackage{relsize}
%\usepackage{graphicx}
\begin{document}
$\underset{i=0} {\overset{\lfloor l/n \rfloor} {\|}}$

$\underset{i=0} {\overset{\lfloor l/n \rfloor} {\Bigg\|}}$
\end{document}