# [OS X TeX] which is real math mode?

Morten Høgholm morten.hoegholm at gmail.com
Mon Dec 12 18:40:07 EST 2005

On Mon, 12 Dec 2005 23:07:14 +0100, Matthew Inglis
<m.j.inglis at warwick.ac.uk> wrote:

>> \begin{displaymath} puts one into a displayed math environment, like to
>> the $$2 + 2 = 4$$ of Plain TeX (which should not be used in LaTeX).
>
> Why shouldn't $$...$$ be used in LaTeX? I have heard several people give
> this advice, but have always cheerfully ignored it with no obvious
> adverse consequences. Can anyone enlighten?

Besided the error checking parts there is also one fundamental difference.
In LaTeX, $...$ means "this is a displayed equation, which I'll put
where the document class told me to." The fleqn option is the most
prominent example of this. $$...$$ is TeX's way of saying "This is a
_centered_ displayed equation. Period.*"

So basically the $$-syntax is in conflict with the LaTeX paradigm unless you are one of those users who use the trick below but if you do that, you should know better. [*] TeX hackers can influence even$$ ...  by using \everydisplay but
don't you do it!
--
Morten
------------------------- Info --------------------------
Mac-TeX Website: http://www.esm.psu.edu/mac-tex/
& FAQ: http://latex.yauh.de/faq/
TeX FAQ: http://www.tex.ac.uk/faq
List Archive: http://tug.org/pipermail/macostex-archives/