# Comma between large functions parameters

My problem is actually quite simple. I have fractions as function parameters, but the delimiting comma doesn't behave properly (i.e. not as I want it to behave). I want the comma to be placed as if the fraction was sitting on the baseline, meaning the comma should be lowered down.

The code looks like this:

B\!\left(\tfrac{n+1}{2}, 2\right)


Actually

B\!\left(\tfrac{n+1}{2}_, 2\right)


looks pretty much how I want it to look like, but then the comma gets too small.

Is there some "proper" way to accomplish this?

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What you want is wrong: the fraction is not sitting on the baseline. –  egreg Jun 30 '12 at 17:35

There is a way. But the result is simply terrible:

\documentclass{article}
\usepackage{amsmath}
\begin{document}
B\!\left(\tfrac{n+1} {\ooalign{%\scriptstyle\hphantom{n+1}$\cr \hidewidth$\scriptstyle2$\hidewidth}% \smash{\rlap{,}}}\,2\right)$
\end{document}


Here's how I'd typeset the whole thing, in descending order of preference:

$B((n+1)/2,2)$

$B\bigl((n+1)/2,2\bigr)$

$B(\tfrac{n+1}{2},2)$


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If you really want to do this, you could try

$B\!\left(\tfrac{n+1}{2}_{\displaystyle ,} 2\right)$


but the result looks awful. Keep in mind that 'TeX knows more about typesetting than many authors do' (Lamport), so it probably has the comma in the best place by default.

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