[texhax] A question with regards to align*

[Toby Cubitt]

Christian Hans Aastrup wrote:
 > Hello there!
 >
 > I'm very happy to display mathematics in
 >
 > \begin{align*}
 > ...
 > \end{align*}
 >
 > and I'm wondering whether it is possible to make LaTeX read
 >
 > $$ .... $$ as \begin{align*} ... \end{align*}???

Probably...but not easy. You'll have to change the catcode of $ to make
it into an active character (not too difficult, but requires familiarity
with low-level TeX), then define macros that expand to the right thing
depending on whether you're opening or closing the environment (no idea
how :) The flexisym and breqn packages from the mh bundle (available on
CTAN) might give you some pointers.

It will undoubtedly be easier to define $$ to be a smart short-cut that
inserts \begin{align*} or \end{align*} as appropriate, assuming you're
using a decent editor (e.g. emacs, vim, or something fairly programmable
-- no flame wars about the definition of "decent", please :)

If you were prepared to use \[...\] instead of $$...$$, then it would
probably just be a case of (untested):

\renewcommand{\[}{\begin{align*}
\renewcommand{\]}{\end{align*}


HTH,

Toby