sign for multiple $\Diamond$-product

Question

I use $\Diamond$ as a product sign and want to have something like $\bigDiamond_{i=1}^{n}$ to note multiple $\Diamond$-products. Similar to $\wedge$ and $\bigwedge$ or $\vee$ and $\bigvee$. Is there a package for this problem?

Answer 1

For such a simple geometric symbol, scaling it seems the easiest road. You might want a larger factor than 1.2 for text style, adjust at will. However, 2 is the right scaling factor for display style.

\documentclass{article}
\usepackage{amssymb,graphicx}

\newcommand{\bDiamond}{\mathbin{\Diamond}}

\makeatletter
\newcommand\bigDiamond{\mathop{\mathpalette\bigDi@mond\relax}}
\newcommand\bigDi@mond[2]{%
  \vcenter{\hbox{\m@th
    \scalebox{\ifx#1\displaystyle 2\else1.2\fi}{$#1\Diamond$}%
  }}%
}
\makeatother

\begin{document}
\[
\bigoplus_{i=1}^n % just for comparison
\bigDiamond_{i=1}^n (a_i\bDiamond b_i)\quad
\textstyle\bigDiamond_{i=1}^n a_i\quad
\scriptstyle\bigDiamond_{i=1}^n a_i\quad
\scriptscriptstyle\bigDiamond_{i=1}^n a_i
\]
\end{document}

Don't use \Diamond for a binary operation or the spacing would be wrong; you need to use \mathbin{\Diamond}, which is what \bDiamond does.