5

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'):

Examples

\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').

7
  • You don't want it to be a math operator, use \newcommand*\conjuntion{\mathbin{\raisebox{-0.25ex}{\textbullet}}}.
    – Manuel
    Apr 1 '15 at 16:23
  • @eduardo.tex: ...or use \mathrel.
    – Werner
    Apr 1 '15 at 16:25
  • @Werner No, \bullet is \mathbin.
    – egreg
    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.
    – Manuel
    Apr 1 '15 at 16:27
5

\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}}}
2

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} 

enter image description here

1
  • 2
    Since you are in math mode \raisebox{\fontdimen22\textfont2}{..} could be a \vcenter{\hbox{..}}.
    – Manuel
    Apr 1 '15 at 17:41

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