[OS X TeX] which is real math mode?

[Morten Høgholm]

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
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