Argthtjtr

This is my first post on this SE so I apologize if my formatting is bad.

Essentially I am trying to reproduce the small black symbol from the following definition in Allen Hatcher's Algebraic Topology:

(This book can also be accessed from his website for free, and this particular image is from page 26.)

I am trying to figure out how to typeset the small black square between the f and the g(s). I tried the following in my preamble

renewcommand{bullet}{tiny$blacksquare$}

but the square bullet produced looks jarring and does not look like a binary operator, i.e. it is not centered and does not have equal spacing between f and g(s).

Would any of you have any suggestions on how to make this particular symbol?

This is actually not a square but just the shape of cdot from the Lucida family used in the picture.

documentclass{article}

usepackage{lucidabr}

begin{document}

$f cdot g$

end{document}

Lucida is a commercial font, you can purchase it from TUG.

You could also go ahead and fake the symbol using a rule.

documentclass{article}

renewcommandbullet{%

  mathbin{mskip1mu

    mathchoice

      {squarebullet{.25ex}{.25ex}}%

      {squarebullet{.25ex}{.25ex}}%

      {squarebullet{.18ex}{.18ex}}%

      {squarebullet{.15ex}{.15ex}}

    mskip1mu}

}

newcommandsquarebullet[2]{vcenter{hbox{rule{#1}{#2}}}}

begin{document}

$f cdot g_{f cdot g_{f cdot g}}$



$f bullet g_{f bullet g_{f bullet g}}$

end{document}

This symbol exists in the mathabx font package. Here is a way to use this symbol without having to load the package:

documentclass{article}

DeclareFontFamily{U}{mathb}{hyphencharfont45}

DeclareFontShape{U}{mathb}{m}{n}%

{<-6> mathb5 %

 <6-7> mathb6

 <7-8> mathb7 %

 <8-9> mathb8 %

 <9-10> mathb9 %

 <10-12> mathb10 %

 <12-> mathb12 }%

 {}

DeclareSymbolFont{mathb}{U}{mathb}{m}{n}

DeclareMathSymbol{sqbullet}{mathbin}{mathb}{"0D}



begin{document}



[ f sqbullet g]%



end{document} 

I don't know the size of the black square as in the picture of the OP. Personally I have tried to build a prehistoric macro to have a black square that could be even smaller if you want (see the 2nd code). For example, I used the package pifont that is available in all types of distribution.

documentclass[12pt]{article}

usepackage{pifont,mathtools,xcolor}

newcommand{sbs}{hspace{.05cm}{rotatebox{90}{ding{122}}}hspace{-.13cm}{rotatebox{90}{textcolor{white}{ding{122}}}}hspace{-.2cm}}

begin{document}



[fsbs g(s)=]



end{document}

Adding scalerel package, you have:

documentclass[12pt]{article}

usepackage{pifont,mathtools,xcolor,scalerel}

newcommand{sbs}{hspace{.05cm}{rotatebox{90}{ding{122}}}hspace{-.15cm}{rotatebox{90}{textcolor{white}{ding{122}}}}hspace{-.2cm}}

begin{document}



$fsbs g(s)=$ 



or



$fscaleto{sbs}{3pt}g(s)=$



end{document}

Decide for the size of the black dot, here it is twice the size of (the bounding box of) a period, with a small sidebearing.

documentclass{article}

usepackage{amsmath}



makeatletter

newcommand{pp}{}% check it's not defined

DeclareRobustCommand{pp}{mathbin{mathpalettepp@relax}}

newcommandpp@[2]{%

  mspace{0.5mu}%

  vcenter{hbox{sboxz@{$#1.$}rule{2htz@}{2htz@}}}%

  mspace{0.5mu}%

}

makeatother



begin{document}



$fpp g$



$scriptstyle fpp g$



end{document}