I'm using the commath package for its nice \od and \pd functions, but I find it uses \tfrac internally. It seems to have an 'if-then' clause to sometimes use \dfrac but it never does so in my tests:
test 1: \od{p}{x}\\
test 2: $\od{p}{x}$
test 3: \(\od{p}{x}\)
Or in align environments either. I don't see any options to control the package behavior. Should I just re-define \od and \pd in my preamble to behave the way I want?
commath provides \textstyle and \displaystyle versions of its \od and \pd (and \md) commands:
\textsyle override: \tod and \tpd\displaystyle override: \dod and \dpd
\documentclass{article}
\usepackage{commath}% http://ctan.org/pkg/commath
\begin{document}
\verb|Normal:| \par
test 1: \od{p}{x} \par
test 2: $\od{p}{x}$ \par
test 3: \(\od{p}{x}\) \par
\bigskip
\verb|\textstyle-version:| \par
test 1: \tod{p}{x} \par
test 2: $\tod{p}{x}$ \par
test 3: \(\tod{p}{x}\) \par
\bigskip
\verb|\displaystyle-version:| \par
test 1: \dod{p}{x} \par
test 2: $\dod{p}{x}$ \par
test 3: \(\dod{p}{x}\) \par
\end{document}
It would be possible to define your own commands doing the same with a slightly different interface (using xparse, say) that could allow you some flexibility.
\tfrac is a forced \textstyle\frac, while \dfrac is a forced \displaystyle\frac. The "normal" \frac is either \textstyle or \displaystyle, depending on the style it is used in. The same holds for the *-\od family above.
\frac switches behaviour between displaystyle and textstyle \od (like almost all commath commands) is broken in that respect and does not usefully switch, only the forced \tod and \dod versions are really useful. (The comath commands all use \ifinner to switch between display and text style versions but that is not a useful test in math mode)
Commented
Feb 23, 2018 at 11:02
\dfrac? It does so in display style\[...\].alignenvironments. I use this by default. Should I be using something else?\dfracand\tfrac, and not necessarily an explanation of why this is the case. Are you interested in a redefinition that uses (say) starred\od*/\pd*for\dfracusage, and\od/\pdfor the\tfracusage?commath. I can redefine the commands myself. I'm wondering if there is some way to do this forcommathvia an option that I've missed. At the same time, if I'm breaking a standard, I'd be happy for an explanation why I should be happy with it the way it is, and that I should change all my existing\fracto\dfracor\tfracinstead...\[environments, and another for\begin{align}. Aren't they similar enviroments? I understand the difference for$and\(compared to\[.