Shortcuts for code in latex

Question

I am tired of writing \frac{\partial something}{\partial something_else}. Can I automate it by defining some sort of shortcut to it, so that when I write \p(x)(y) it will transform to \frac{\partial x}{\partial y}?

Answer 1

\documentclass{article}

\usepackage{amsmath}

\newcommand\p[2]{\frac{\partial #1}{\partial #2}}

\begin{document}
    $ \p{x}{y} $
\end{document}

Answer 2

The ability to define complex macros is one of the strengths of LaTeX. The traditional LaTeX way would be to use \p{x}{y} in the text instead of \p(x)(y). If you are happy with \p{x}{y}, then you can just add

\newcommand{\p}[2]{\frac{\partial#1}{\partial#2}}

to your preamble. Since this new macro is requires mathmode, you may also want to wrap the macro in an \ensuremath so something like

\newcommand{\p}[2]{\ensuremath{\frac{\partial#1}{\partial#2}}}

If you really want \p(x)(y) then you can add

\def\p(#1)(#2){\ensuremath{\frac{\partial #1}{\partial #2}}}

to your preamble. This isn't particularly robust in that something like $\p((a+b)(a-b))(a+b)$ will break it. There are ways to make it more robust including LaTeX3, however, I would advise against using \p(x)(y) unless there is a good reason (especially as a beginner).

One final note is that it is probably better to use a slightly longer and more descriptive names for macros. While \p seems good now, in a few months it likely will not mean anything to you. Short macro names also increase the chances you might run into a name clash with some other package.

Answer 3

The commath package has a lot of these handy macros already defined, like \pd[2]{f}{x}. I happen to use it, but it also has some nasty issues, like incorrect detection of inline vs. display math, and a conflict with TikZ over the colon character (see Why does pdfTeX hang on this file?).