5

I'd like to create a symbol do deal with repeated applications of an arbitrary associative operation *. Something like:

enter image description here

But this is not good looking to me. The proportions on the left hand doesn't pleases me.

Does anyone have any idea on how to improve it?

Thanks.

Ari Brodsky
  • 2,596
Dion
  • 696

2 Answers2

8

The solution in https://tex.stackexchange.com/a/306593/4427 can actually be used for all symbols that already lack a “big” version.

\documentclass{article}
\usepackage{graphicx}
\usepackage{amsmath}

\makeatletter
\newcommand{\bigsymbol}[1]{%
  \DOTSB
  \mathop{% we want it to be an operator
    \mathchoice{\big@symbol\displaystyle\Large{#1}}
               {\big@symbol\textstyle\large{#1}}
               {\big@symbol\scriptstyle\normalsize{#1}}
               {\big@symbol\scriptscriptstyle\small{#1}}%
    }\slimits@
}

\newcommand{\big@symbol}[3]{%
  \vcenter{%
    \sbox\z@{$#1\sum$}%
    \dimen@=0.875\dimexpr\ht\z@+\dp\z@\relax
    #2% font size
    \hbox{\resizebox{!}{\dimen@}{$\m@th#3$}}%
  }%
  \vphantom{\sum}%
}
\makeatother

\newcommand{\bigast}{\bigsymbol{*}}

\begin{document}
Here's in text, $\bigast_{i=1}^n x_i$, next in display
\[
\bigast_{i=1}^n x_i=x_1*x_2*\dots*x_n
\]
\end{document}

enter image description here

egreg
  • 1,121,712
1

not as general as the one egreg just posted, but simpler:-)

enter image description here

\documentclass{article}

\usepackage{amsmath}

\newcommand\bigast{\mathop{\mathchoice{\hbox{\large$\ast$}}{\ast}{\scriptstyle\ast}{\scriptscriptstyle\ast}}}

\begin{document}

\[\bigast_{i=1}^n x_i = x_1\ast\dots\ast x_n\]


$\bigast_{i=1}^n x_i = x_1\ast\dots\ast x_n$

\end{document}
David Carlisle
  • 757,742