I often use short macros in mathematical formulas for frequently used symbols, e.g. \d x for a differential dx or, say, \v if I need a vector v very often in my text to make things more readable.
However, I get a clash with predefined macros because \d stands for a dot under the next character and v for the hacek accent, which I don't want to override (maybe I need them in the bibliography…).
So, I came up with the following to override those macros only in math mode:
\documentclass{article}
\usepackage{everyhook}
\newcommand{\mathdef}[2]{%
\PushPostHook{math}{\expandafter\def\csname #1\endcsname{#2}}%
\PushPostHook{display}{\expandafter\def\csname #1\endcsname{#2}}}
\mathdef{d}{\mathrm{d}}%
\begin{document}
\d x is an x with a dot below and $\int f(x) \d x$ is an integral over $x$.
\end{document}
However, I would like the command to be defined like normal macros too, i.e. \mathdef{\d}{\mathrm{d}}, and also be able to take arguments, but all my experiments with expandafter, unexpanded, etc. didn't work out and led only to the usual strange error messages. Any hint how I can do that?
Furthermore, do you think there is a big performance penalty using \everymath like that in a large document?
Best Answer
My idea is very similar to egreg's, but I'd like to add an optional argument, so the math command could process arguments itself. The code:
The result: