# Is there a (fork) symbol for probabilistic causality? Logic

I found pitchforks, but none that is similar to these explaines in Salmon 1989

Thanks!!

• Maybe $\supset\mkern-15mu-_u$ – Steven B. Segletes Sep 27 '16 at 12:37
• Hi CarlaTex, thanks! I saw this list, but the symbols are a bit different. Thanks again. – Oliver Amundsen Sep 27 '16 at 12:39
• Hi Steven, it did! thanks a lot! Maybe you want to add this as an answer and provide the context? thanks a lot! – Oliver Amundsen Sep 27 '16 at 12:40
• Just for fun: \documentclass{article} \usepackage{marvosym} \usepackage{graphicx} \begin{document} \rotatebox{90}{\Neptune} \end{document} :) – user36296 Sep 27 '16 at 15:37

Since it should be a connective, the type is \mathbin; then we can use TeX's rules for relations:

\documentclass{article}

\newcommand{\fork}{%
\mathbin{%
\supset
\mathrel{\mkern-9mu}%
\mathrel{-}%
}%
}

\begin{document}

The connective for the fork is $\fork$
and we can write $a\fork b$ or also
$a\fork_u b$.

\end{document}


Choose the kerning based on your liking.

At its simplest, I propose a simple overlap of a \supset and a -, with a kern to effect the overlap. However, A Rmano notes, this may not have the proper spacing relative to adjacent material. Thus, if one wishes a general symbol, that works across math styles, I have provided here \fork.

EDITED for \mathbin instead of \mathrel.

\documentclass{article}
\usepackage{scalerel}
\newcommand\fork{\mathbin{\ThisStyle{{\supset}\kern-\dimexpr.5\LMex+3pt\relax{-}}}}
\begin{document}

$\supset\mkern-15mu-_\mathrm{u}$

$\fork_\mathrm{u}$
$\scriptstyle \fork_\mathrm{u}$
$\scriptscriptstyle \fork_\mathrm{u}$
\end{document}


• Hmmm... I think that the _mathrm{u} should go into the mathrel --- otherwise it's strange. Try $A fork_\mathrm{u} B$ versus $A \mathrel{\supset\mkern-15mu-_\mathrm{u}} B$... maybe an optional argument? – Rmano Sep 27 '16 at 12:54
• @Rmano The initial version may indeed have the wrong spacing, and I showed it to convey the gist of the approach. For regular use, I certainly endorse the use of \fork as the preferred embodiment. – Steven B. Segletes Sep 27 '16 at 13:38
• Yes... but $A\fork_u B$ has still the wrong spacing, because the _u should go into the mathbin, no? Or am I wrong? (can't check now...) – Rmano Sep 27 '16 at 14:21
• @Rmano I don't know enough about the contextual meaning of the symbol and its usage to know the answer to your question. I would just note that egreg, who would know the answers to these questions, did not place the subscript inside the \mathbin. – Steven B. Segletes Sep 27 '16 at 14:38

Mnsymbol and Mdsymbol have \rightpitchfork glyphs (and indeed quite a few other pitchforks). Here is a way to use it, along with \leftpitchfork, without loading Mnsymbol. In addition , I defined an extensible version \xleftfork. They have bold versions.

\documentclass[12pt]{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{lmodern, mathtools}

\DeclareFontFamily{U}  {MnSymbolA}{}
\DeclareSymbolFont{MnSyA}         {U}  {MnSymbolA}{m}{n}
\SetSymbolFont{MnSyA}       {bold}{U}  {MnSymbolA}{b}{n}
\DeclareFontShape{U}{MnSymbolA}{m}{n}{
<-6>  MnSymbolA5
<6-7>  MnSymbolA6
<7-8>  MnSymbolA7
<8-9>  MnSymbolA8
<9-10> MnSymbolA9
<10-12> MnSymbolA10
<12->   MnSymbolA12}{}
\DeclareFontShape{U}{MnSymbolA}{b}{n}{
<-6>  MnSymbolA-Bold5
<6-7>  MnSymbolA-Bold6
<7-8>  MnSymbolA-Bold7
<8-9>  MnSymbolA-Bold8
<9-10> MnSymbolA-Bold9
<10-12> MnSymbolA-Bold10
<12->   MnSymbolA-Bold12}{}

\makeatletter
\newcommand{\xleftfork}[2][]{%
\ext@arrow 0079\xleftforkfill@{#1}{#2}%
}
\newcommand{\xleftforkfill@}{%
\arrowfill@\Mnrelbar\Mnrelbar{\mathrel{\leftpitchfork}}
}
\newcommand{\xrightfork}[2][]{%
\ext@arrow 0097\xrightforkfill@{#1}{#2}%
}

\DeclareMathSymbol{\rightpitchfork}{\mathrel}{MnSyA}{"88}%
\DeclareMathSymbol{\leftpitchfork}{\mathrel}{MnSyA}{"8A}%
\DeclareMathSymbol{\Mnrelbar}{\mathrel}{MnSyA}{"D0}%

\begin{document}

$A \rightpitchfork B\enspace B \leftpitchfork A$
\bigskip

\boldmath      $A \rightpitchfork B\enspace B \leftpitchfork A$
\bigskip

$C \xleftfork{\text{an extensible pitchfork}}D$

\end{document}


• I don't think the extensible pitchfork is useful but it looks nice :) +1 – Henri Menke Sep 27 '16 at 15:40
• It was asked for not long ago on this site. I tried for fun to obtain an extensible pitchfork with a \rightpitchfork on the left, but didn't succeed (missing $was the error message…) – Bernard Sep 27 '16 at 15:50 In Unicode there is the similar symbol \nisd. However, it is a relation rather than a binary operator. It is not available in all fonts but XITS has it. \documentclass{article} \usepackage{unicode-math} \setmathfont{XITS Math} \begin{document}$a \nisd b\$
\end{document}