[Tex/LaTex] \star vs. \ast in formulas. Which one to use

math-modesymbolstypography

When you read a formula aloud you say "r and r-star are related by this formula".
If you write this formula down you normally write an r with a six-handed star, which would actually be an asterisk and not star (with 5 sharp hands) because it's easier to draw by hand.

But what to do when typing this formula in LaTeX? Should I set it as I pronounce it?

r^\star = a r

Or as I write it by hand?

r^\ast = a r

And will \ast always do the same as *?

r^\ast == r^* %???

Is one (\star or \ast) simply wrong (typographically or semantically) or is it just a matter of personal preference?

Best Answer

I think it's just personal preference. In the standard setup * and \ast are the same.

fontmath.ltx has

\DeclareMathSymbol{*}{\mathbin}{symbols}{"03} % \ast
\DeclareMathSymbol{\ast}{\mathbin}{symbols}{"03}

So both pick up character 3 from the symbol font with infix binary operator spacing.

Related Solutions

[Tex/LaTex] Tagging equations with three \ast

Here's my attempt. It's not ideal. And it borrows from Ian Thompson's answer in its use of the two commands, one for the symbol, one to protect it. It is more compact that Ian's and uses \shortstack rather than tabular. EDIT: I've changed the adjustments to be in ex rather than pt on egreg's suggestion. I've also got rid of the \ensuremath{\displaystyle… stuff I had before which I thought I needed...

\newcommand\iiiastsym{\raisebox{-.5ex}{\shortstack{%
  \(\ast\)\\[-.5ex]%
  \(\ast\ast\)}}%
}
\newcommand\iiiast{\protect\iiiastsym}

three asts as a triangle

By way of comparison, here are the proposed solutions:

enter image description here

Warning: egreg's solution has been changed as compared to the way he gave it in order for it to display. Namely, I've put it inside \( and \) for mathmode and I've removed a # which is needed because the doubled ## is for use inside a \newcommand...

[Tex/LaTex] \star printing as \ast

Computer modern has a star symbol. Since it is a rather stylistic symbol let's use it:

\documentclass[10pt]{article}
\usepackage{times}
\begin{document}    
    \newcommand{\mystar}{{\fontfamily{lmr}\selectfont$\star$}}

    Foo\mystar bar*
\end{document}

enter image description here

Best Answer

Related Solutions

[Tex/LaTex] Tagging equations with three \ast

[Tex/LaTex] \star printing as \ast

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