# Typesetting a small function with Big parameters

I have a small function that needs to take big parameters. Right now I think that the function part looks too small and implicitly suggests it might be some kind of multiplication instead of an evaluation.

\newcommand{\rect}{\mathrm{\textbf{rect}}}
...
$$\left[(\rect_\ell) \ast (f\ast g)\right]\left( x+\frac{2i-1}{2k},y+\frac{2j-1}{2k}\right)$$


It looks like this & I think its ugly:

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Does a look which uses \bigl and \bigr instead of \left and \right, i.e., making sure that the outer brackets and parentheses have the same size, meet your needs?

\documentclass{article}
\usepackage[euler-digits]{eulervm} % educated guess about fonts
\usepackage{palatino}
\newcommand{\rect}{\textbf{rect}} % don't use \mathbf as that would load Computer Modern
\begin{document}
before:

$$\left[(\rect_\ell) \ast (f\ast g)\right] \left( x+\frac{2i-1}{2k},y+\frac{2j-1}{2k}\right)$$

\medskip

after:

$$\bigl[(\rect_\ell) \ast (f\ast g)\bigr] \bigl( x+\frac{2i-1}{2k},y+\frac{2j-1}{2k}\bigr)$$
\end{document}

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Here's my proposals; my preferred one would be the last, without outer parentheses.

\documentclass{article}
\usepackage{mathpazo}
\usepackage[euler-digits]{eulervm}
\usepackage{amsmath}

\newcommand{\rect}{\textbf{rect}} % simplify definition of \rect

\begin{document}
Displayed
\begin{gather}
\bigl[(\rect_{l}) \ast (f\ast g)\bigr]
\bigl(x+\tfrac{1}{2k}(2i-1),y+\tfrac{1}{2k}(2j-1)\bigr)
\\
\bigl(\rect_{l} \ast (f\ast g)\bigr)
\bigl(x+\tfrac{1}{2k}(2i-1),y+\tfrac{1}{2k}(2j-1)\bigr)
\\
\rect_{l} \ast (f\ast g)
\bigl(x+\tfrac{1}{2k}(2i-1),y+\tfrac{1}{2k}(2j-1)\bigr)
\end{gather}
Text:\\[1ex]
$\bigl[(\rect_{l}) \ast (f\ast g)\bigr] \bigl(x+\tfrac{1}{2k}(2i-1),y+\tfrac{1}{2k}(2j-1)\bigr)$\\[1ex]
$\bigl(\rect_{l} \ast (f\ast g)\bigr) \bigl(x+\tfrac{1}{2k}(2i-1),y+\tfrac{1}{2k}(2j-1)\bigr)$\\[1ex]
$\rect_{l} \ast (f\ast g) \bigl(x+\tfrac{1}{2k}(2i-1),y+\tfrac{1}{2k}(2j-1)\bigr)$
\end{document}


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