# [OS X TeX] OT: spacing after operator in math

Frank STENGEL fstengel at mac.com
Fri Dec 22 13:26:08 EST 2006

```Le 22 déc. 06 à 19:08, Bruno Voisin a écrit :

<snip>

> As far as I can tell, the fact that \sign is defined as an operator
> (\mathop) ensures that some space will be added before its
> argument. I'm seeing journal-specific macros which use instead:
>
> \newcommand{\sign}{\mbox{sign}}

Yuck! At least one could write

\newcommand{\sign}{\mathop{\mbox{sign}}}

to get halfway proper spacing

>
> which I think is wrong. In particular, that would prevent the above
> standard space to be added before the argument. I have seen also
> stuff like \newcommand{\sign}{\mbox{sign}\;}, which doesn't feel
> right either.

Indeed

>
> But what the heck is this space? Is this some hard-coded value
> inside the source code of TeX itself, or some accessible and
> clearly defined parameter within plain TeX or LaTeX?

It seems to be hard-coded in TeX. There is a table explaining what
kind of space is added when in chapter 18 of the TeXBook (p170 in my
copy). The TeX primitives \mathop, \mathrel, \mathopen, \mathclose
etc. will adjust spacing around their arguments.

HTH
--
Frank STENGEL (fstengel<at>mac.com)