I would like to get a macro \of to define a function with an optional macro \at to define its restriction. The reason is, that I don't like the spacing for functions (as there is no spacing) and I would like to automate that. The idea is, to set functions like f \of x or f\of x which would be quick and handy. But I am not sure, if that is doable for syntax reasons. I think, something like \func{f}{x} would be much easier to provide, but that would be too much typing and quite a lot of change for already existing formulae.

However, the reasons for this macro are the following properties which I would like to achieve. In future I want to expand this to all kind of derivatives or alike (total, partial, normal, increment, infinite element...).

Here is the list:

  • Always set argument (value behind \of in ()
  • Recognize x, (x), and {x} as argument
  • always set half space in front of the function when it is set behind a letter, number or bracket
  • set half space behind the function, if followed by a (
  • allow powers to the function and to the argument and set it properly
  • allow nested functions
  • allow \at-notation with three optional formats (this will get interesting later on for the derivatives...)

And here are some examples:


\begin{verbatim}f \of x=x^2\end{verbatim}
\begin{verbatim}f \of (x+y)=x+y\end{verbatim}
\begin{verbatim}f \of (x+y)x+y\end{verbatim}
\begin{verbatim}f \of (x+y)(x+y)(x+y)\end{verbatim}
\begin{verbatim}xf \of xx\end{verbatim}
\begin{verbatim}zf \of xg \of yz\end{verbatim}
\begin{verbatim}f^2 \of x\end{verbatim}
$f^2(x) \vee f(x)^2 \vee (f(x))^2 \quad \text{don't know which one is correct}$
\begin{verbatim}f \of x^2\end{verbatim}
\begin{verbatim}f \of g \of x\end{verbatim}
\begin{verbatim}\frac{a}{b}f\of x\end{verbatim}
\begin{verbatim}(a+b)f\of x\end{verbatim}
\begin{verbatim}\setFunctionAtBar \end{verbatim}
\begin{verbatim}f \of x \at a\end{verbatim}
\begin{verbatim}f \of x \at {a+b}\end{verbatim}
\begin{verbatim}f \of x \at (a+b)\end{verbatim}
  • 3
    latex goes to a lot of effort to have a consistent syntax \frac{a}{b} not a \over b, \hspace{2in} not \hskip 2in etc :( Commented Sep 20, 2013 at 11:37
  • hmmm, I will think of an other notation, which would be easy. But is there something around, doing the other stuff? I got the feeling, there has to be something, but I can't find it.
    – LaRiFaRi
    Commented Sep 20, 2013 at 11:56
  • 3
    Something like $(a+b)\,f(x)$ or (f(x))_{}, ie. inserting things way before \of is almost impossible without making things active or pre-processing the whole content. The \of doesn't know what came before it. (You can however put \mathinner{(a+b)} which, I believe, includes spacing around it.) Otherwise this is probably doable with a few ifnextchars, but do you really want that (see David's comment)? xparse can probably help with a \func macro. Commented Sep 20, 2013 at 12:06
  • I already gathered that the syntax is the major problem. But your point about pre-processing is very interesting. I will have a look on xparse when CTAN is on again.
    – LaRiFaRi
    Commented Sep 20, 2013 at 12:10

1 Answer 1


Aside from syntax it seems main issue is spacing before a function term. TeX will add space there automatically if it knows it is a function. \log \sin etc are \mathop atoms and get space, but f is a mathord so does not. If you declare a one-letter math operator though, it gets the space that I think you want:

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