# How to mimic spacing around \bullet with \DeclareMathOperator?

I'm trying to define \conjunction by means of \textbullet instead of \bullet, since the latter looks too big in logical formulas. How can I make the spacing around \conjunction to behave like the spacing around \bullet when there is an opening parenthesis just after it?

Compare (2) and (2'):

\documentclass[12pt]{article}
\usepackage[paperwidth=10cm,paperheight=7cm,margin=1em]{geometry}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{ebgaramond-maths}

\DeclareMathOperator\conjunction{\raisebox{-0.25ex}{\textbullet}}

\begin{document}\begin{align}
\intertext {Good spacing but bad size:}
(\exists x(\forall y(\phi(y)\equiv y\!=\!x)&\bullet Gx)\supset\psi)\\
\exists  x(\forall y(\phi(y)\equiv y\!=\!x)&\bullet (Gx\supset\psi))\\
\intertext {Good size and spacing:}
(\exists x(\forall y(\phi(y)\equiv y\!=\!x)&\conjunction Gx)\supset\psi)\\
\intertext {Good size but bad spacing:}
\exists  x(\forall y(\phi(y)\equiv y\!=\!x)&\conjunction (Gx\supset\psi))
\end{align}\end{document}


This won't do:

\DeclareMathOperator\conjunction{\raisebox{-0.25ex}{\textbullet\ }}


because it adds an unwanted extra space to (1').

• You don't want it to be a math operator, use \newcommand*\conjuntion{\mathbin{\raisebox{-0.25ex}{\textbullet}}}. Apr 1 '15 at 16:23
• @eduardo.tex: ...or use \mathrel.
– Werner
Apr 1 '15 at 16:25
• @Werner No, \bullet is \mathbin. Apr 1 '15 at 16:25
• @egreg: True, if \conjunction is a binary operator.
– Werner
Apr 1 '15 at 16:27
• @egreg I don't understand what's the text about, but may be OP was using \bullet because of the symbol while the correct would be a mathrel. Apr 1 '15 at 16:27

\DeclareMathOperator is only for \log-like functions. Here you want this symbol to be a binary operator, so you need \mathbin

\newcommand*\conjunction{\mathbin{\raisebox{-0.25ex}{\textbullet}}}


A simple solution with pict2e. The bullet size can be adjusted, via an optional argument (default: 2.1\unitlength):

\documentclass[12pt]{article}
\usepackage[paperwidth=10cm,paperheight=7cm,margin=1em]{geometry}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{ebgaramond-maths}
\usepackage{graphicx, pict2e}

\newcommand\conjunction[1][2.1]{\mathbin{\raisebox{\fontdimen22\textfont2}{\circle*{2.1}}}}

\begin{document}

\begin{align}
\intertext {Good size and spacing:}
( ∃ x(∀ y(ϕ(y) ≡ y\!=\!x) & \conjunction Gx) ⊃ \psi)
\end{align}

\end{document}


• Since you are in math mode \raisebox{\fontdimen22\textfont2}{..} could be a \vcenter{\hbox{..}}. Apr 1 '15 at 17:41